AUDIO – June; 1955

JUNE, 1955

504

ENGINEERING MUSIC SOUND REPRODUCTION...a.' CN -.tar N -Qu\P pNpGßQ e P N 60i, 3Z.pa$ \ c w

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TVAL INPUT

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The search for more power, lower di:tor:ior, and better listening quality goes on ad infini_um. Using secordary emissio-z tubes in a cross -coupled phase splitter and four KT456's in the output stage, one author chains great improvement. See page 15. This elaborate installation is capable of giving recording studio quality -it has to be for its owner is a recording technician. Amu) IN THE HOME takes us to see it, describes it thoroughly. See page 18.

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40 to 15,000 cycles response at 71/2 in /sec. Over 55 db. signal -to -noise ratio Flutter and wow under 0.25% rms. Today the Ampex 600 is a tape recorder in a class by itself. Separate record and playback heads to permit At $545 it provides a degree of fidelity that is beyond reproach monitoring while recording - and it is a modest machine that weighs only 28 pounds. Built -in mixing between microphone and line It is a professional recorder priced within reach of thousands Prices - $498 unmounted, $545 in portable case of critical music listeners and tape recording enthusiasts.

n 1947 this same class of fidelity could only be had by buying an Ampex 200 for $5200. It was worth its price because it A companion unit that not only matches the 600 in portability and oppearance, but also in quality as was the was only thing of its kind. It the first commercial re- well. Price is $149.50 in portable case. corder that made radio transcriptions sound like live broadcasts. But the Ampex 200 weighed 250 pounds. Few, if any, were bought for home use.

The man who has seen it all has this to say: 4

"When I bought the first Ampex Model 200, folks thought I was a goner, springing for $5200.00. But it was a bargain - transcribing my radio program without losing any of the fresh- ness of a live appearance. Some of my records came off the same tape. I could be three places at once. But now here's an Ampex I can carry with one hand. Records and reproduces perfectly, but costs little compared with the first one. So I have a commercial recording studio wherever I roam."

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JUNE, 1955 VOL. 39, No. 6 Successor to RADIO, Est. 1917.

AUDIO f. \1.I\Fa.111 , itt :sic sot 'o RF.PRIInI 4770\' C. G. McProud, Editor and Publisher Henry A. Schober, Business Manager Ilarrie K. Richardson, Associate Editor Florence Rowland, Production Manager Edgar E. Newman, Circulation Director

Sanford L. Cahn, Advertising Director lu dastry Special Representatives - "Workhorse" H. Thorpe Covington and Dick Knott, 7530 Sheridan Road, Chicago 30, Ill. `, Nid West Representative - San ford R. Cowan, 67 West 44th St., 635 New York 36, N. Y. BROADCAST DYNAMIC West Coast Representatives - MICROPHONE lames C. Galloway and I. W. Harbison, 816 West 5th St., Los Angeles 17, Calif.

CONTENTS Audio Patents -Richard H. Dorf 2 USED ON New Literature 5 Letters 6 TV London Letter -Richard Arbib 8 Editor's Report 12 AND A High -Power Amplifier with Minimum Distortion -Bruce DePalma 15 At Home with Audio -Lewis C. Stone 18 Negative Feedback-Edgar M. Villchur 22 BC A Novel Tape Recording Amplifier-A. F. Fischman 24 Phonograph Equipment -A complete 32 -page section 25 Uniform high quality performance day- after -day Record Revue Edward Tatttall Canby 57 in studio and remote - pick -ups has proved Equipment Report the rugged -Crestwood 304 Tape Recorder, "Dual" Record Player - dependability of the "635 ". Pilotrol Preamplifier-F_qualiser 60 Exclusive E -V Acoustalloy New Products 64 diaphragm assures smooth, Audio E T C-Edward Tatnall Canby 68 peak -free response 60 to 13,000 cps. Output is db. 50 -250 Coming Events 69 -55 ohms impedance selector. Tiltable Employment Register 91 head. %"-27 thread. Cannon XL -3 About Music - Harold Lawrence 72 connector. 18 ft. cable. Industry Notes and People 79 List Price $75.00 Advertising Index A0 Normal trade discount applies. See your Authorized E -V Distributor or Write for further information. AUDIO (title registered U. S. Pat. Off.) Is published monthly by Radio Magazines, Inc., Henry A. Schober, President: C. O. hIcProud, Secretary, Execut.re and Editorial Offices, 204 Front St., Mineola, N. Y. Subscription rato -U. 8. NO FINER CHOICE THAN Possessions, Canada and Mexico, $4.00 for one year, $7.00 for two years, all other countries, $5.00 per year. Single copies 50c. Printed in U. S. A. at Lancaster, Pa. All rights reserved. Entire contents copyright 1955 by Radio Mega. vino, Inc. Entered as Second Class Matter February 9, 1950 at the Post Off ce, Lancaster, Pa. under the Act of March 3. 1879. gieeMS,CC RADIO MAGAZINES, INC., P. O. Box 629, MINEOLA, N. Y. BUCHANAN MICHIGAN AUDIO JUNE, 1955 1

www.americanradiohistory.com Ersin Multitore Solders

America's most complete line AUDIO PATENTS

RICHARD H. DORF* 1

TlIE USUAL AUTOMATIC gain control, point (selected by adjusting the delay bias. limiter, or volume compressor operates no doubt) despite increases of several on the basis that a negative -going d.c. hundred times at the input point. control voltage derived from the signal is Just what happens to the tube's operating applied to the grid of a control tube, usually point when the grid voltage is played a variable -mu tube, which reduces the gain around with in this manner we have not of the stage as the signal input level in- bothered to figure out. Very likely R. creases. Angus A. Macdonald of Catons- creates enough additional voltage drop ville, Md., is the inventor of a volume - when the grid goes negative and plate cur- limiting device which does not affect the rent increases to help keep actual bias fairly ROTARY POWER gain of the amplifier but actually limits the constant. Or perhaps it doesn't matter in IS BEST signal itself at the grid of a voltage- ampli- he "clop- clop" of this application. Anyway, the inventor says Old Bess" gave fier stage by voltage- divider action. Al- it works and in this column we generally Grandma's buggy ride though the inventor states in his preamble take his word if it doesn't look too out- more vibration thon the smooth Rotary Power that his device obviates the disadvantages rageous. He says the system can be used of today's modern au- of the usual types, he does not specify with any voltage -amplifier stage, and that tomobiles. ROTARY just what the gains over the prior art are. parameters should be adjusted initially for POWER is best for mo bile radio, too He has at least come up with something normal operation without control voltage. and for all DC to AC different and interesting, covered by Patent Naturally, higher signal levels initially can r conversion ... smoother No. 2,703,825, which is assigned to West- be handled by low -mu than by high -mu . . . more dependable. inghouse. tubes. The control voltage can, of course, DC TO AC CONVERTERS One circuit of his invention is shown in he derived from anyplace, the method of Fig. 1. Signal comes in through blocking Fi,q. 1 being only a for -instance. Delay bias capacitor Cs and passes through R, to the is also a matter of choice and need not be For operating tape re- is corders, dictating ma- grid of V,, which the amplifier stage. used at all. chines, amplifiers and Output is taken in the usual manner other 110 -volt radio - across plate resistor R, through blocking audio devices from DC or storage batteries. Used Cut Signalling by broadcast studios, program producers, exec- capacitor C,, R. is an unbypassed cathode - utives, salesmen and other "field workers ". bias resistor. Attell B. Anderson has recently been Output signal from the amplifier tube granted Patent No. 2,703,344, which con- DUO -VOLT GENEMOTORS is also passed through blocking capacitor tains some interesting implications in the The preferred power sup- C, to the grid of V,, which is the signal field of signalling and warning of blind and ply for 2-way mobile radio ¡ rectifier which produces the d.c. installatio ns. , control deaf persons by passing currents through from either 6 or 12 -volt batteries. Carter Gene - voltage. A negative delay bias may also be the skin. The patent, which is assigned to motors are standard equipment in leading makes connected to the grid of V, to prevent any Bell Labs, should be read by anyone much of auto, aircraft, railroad, utility and marine communications. control action until the signal level reaches interested and we will just skim the sur- a certain maximum point. The delay bias face here. CHANGE -A -VOLT DYNAMOTORS keeps V, at or near cutoff under no- signal The general idea is that if electrodes are or low -signal conditions. Operates 6 -volt mobile rodio attached to the skin, the wearer can detect sets from 12 -volt automobile When the signal reaches the level at changes in both the level and the frequency batteries ... also from 24, 32 which limiting is to begin, its voltage at of alternating currents passed by the elec- and 64volt battery power. One of many Carter Dynamo- the grid of V, is sufficient to overcome the trodes through the skin. As long as the tor models. Made by the delay bias. V, begins to conduct and cathode level is kept below about 10 db above 1 world's largest, exclusive man- current passes through cathode resistor R., 100 cps, the ufacturer of rotary power sup ma and between and 10,000 plies. electrons moving from ground to cathode sensation received is similar to tactile and creating, as usual, a pulsating d.c. stimulation (translation from patentese: BE SAFE . , . BE SURE . . . BE SATISFIED AC can be produced by revers- voltage at the cathode which is positive ing the flow of DC, like throw- with respect to ground. This voltage is ing a switch 120 times a sec- filtered by C,, C,, and R5, so that it passes ond. But ROTARY converters actually generate AC voltage through R, and R, to the grid of V, as from on alternator, some as pure d.c. 8+ utility stations. Thot is why The positive voltage at the grid of I ROTARY power is such clean R7 NEGATIVE AC, so dependable ... essen- causes V, to draw grid current. In ac- V2 DELAY tial for hash -free operation of cordance with normal tube action, the BIAS recorders from DC power. positive grid voltage lowers the impedance R6 MAIL COUPON for illustrated bulletin between grid and cathode, the magnitude G5 Be with complete mechanical and of this impedance at any time being in- CI electrical specifications and cerformance charts. Carter Motor Co., Chicago 47. versely dependent on the magnitude of the positive control voltage. The grid -cathode R3 f C2 R5 C4 impedance of V, is the shunt leg of a SIGNAL CARTER MOTOR CO. voltage divider, the series leg of which is OUTPUT 2648 N. Maplewood Ave. E R4 Chicago 47, Illinois R,. The signal passes through this divider, - C3 and as the grid-cathode impedance be- VI -li comes lower, the signal voltage on the grid SIGNAL R1 Please send illustrated literature containing com INPUT plete information on Carter "Custom" Con -1 also decreases. According to the patent, verters and Dynamotor Power Supplies s the grid voltage can, in this manner, be R2 NAME kept from increasing beyond a certain

Address * Consultant, 255 W. 84th State Electronics City SE, New York 24, N. Y. Fig. 1. AUDIO JUNE, 1955 2

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AUDIO JUNE, 1955 3

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touch) and is not painful or uncomfort- inch square and separation of at least 1/8 able. However, the electrodes must have a inch. Another electrode structure comprises sub - miniature audio certain minimum size and separation so several concentric electrodes, adjacent as not to give too high a current density. groups of two constituting each circuit. At frequencies up to 5,000 cps, changes Presumably the subject would learn to TRANSFORMERS in level are more easily detected than those localize the sensations and determine from of acoustical signals are by the ear. Fre- which set the stimulation came. quency discrimination is relatively poor Speech signals are not, of course, the but does exist. The inventor's idea is to only type which can be used. In addition employ such amplitude and frequency sen- to any of many signals to indicate various sitivity as does exist, combined with multi- conditions, one good use might be with ple sets of electrodes placed at different the radar -like obstruction -detecting devices parts of the body and carrying different which have been under development for pieces of the intelligence, to convey in- the blind for some years. These signal formation to the subject. distances to obstructions by time separa- The basic device used to transmit signals tion of the transmitted and received signals, to the electrodes might be simply an input and the cutaneous receiving method might device and amplifier. However, things work be desirable, not only for the deaf blind out better if something equivalent to the but also for the hearing blind who would block diagram of Fig. 2 is used-a signal like to reserve their hearing for normal source, equalizer, clipper, and amplifier. use in hearing what goes on about them Figure 3 shows the form such a system without confusion from ranging beeps. might take. The sound source is a microphone. Human speech has most of its content in the region around 400 cps so the equalizer is used to give a low -frequency Recorder Failure Alarm ,attenuation beginning at about 1000 cps: this makes the input signals roughly equal While we doubt that the problem solved over the spectrum. The peak clipper gets by this patent is very important, we report rid of the signal peaks which might cause it for what it is worth. German inventors, pain or be outside the region of amplitude Wolfgang Stoff and Egon Neumann, have a discrimination. The amplifier has positive patent on a system of signalling the failure feedback so that its effective output im- of a magnetic recording circuit. The in- pedance is high and it is essentially a convention, Patent No. 2,703,877, is assigned stant- current device. This is desirable to (take a breath) Leowe Opta Aktienge- because the resistance of the skin varies sellschaft. with moisture, pressure, heat, and the like, The idea, for which no drawing is really and if the signals were of a constant - necessary, is to hang on to the output of the voltage nature the current would vary recording amplifier a circuit tuned to the widely, destroying the subject's ability to frequency of the fundamental or a harmonic fre- Especially designed discriminate. of the bias -oscillator frequency. This This is, of course, only one section of a quency is then made to operate a plate - Printed Circuits and speech system. Since frequency discrimina- circuit relay through a tube. When some- Transistor applications tion by this method is poor, it would be thing goes haywire in the amplifier or bias desirable to separate the speech into several circuit, the bias signal, which normally goes frequency ranges by means of filters, each through the amplifier or is injected in AS LISTED IN TRIAD'S NEW band then being passed through a separate somehow, disappears. The relay then drops and causes bells to ring, sirens to sound, 1955 GENERAI CATALOG amplifier to a separate set of electrodes out located at a different portion of the body. lights to flash. . . . One suitable electrode structure would If this patent or any other one is worth be a pair of conducting "buttons" fixed in a quarter to you, send your two bits to a nonconducting block and strapped to, say, The Commissioner of Patents, Washington the wrist. For this structure the inventor 25, D. C., who will send you a copy pro- suggests electrode area of no less than 3/16 vided you have given its number.

Fig. 3

1955 4 AUDIO JUNE,

www.americanradiohistory.com NEW LITERATURE HOW YOU CAN ADVANCE Switchoraft, Inc., 1325 N. Halsted St., Chicago 22, III., announces publication of a new condensed four -page catalog No. IN CS -55, containing description and technical specifications of more than 200 electronic components, Including many recent additions to the Switcheraft line. Of par- ELECTRONICS ticular interest to users of audio equipment are the Switchcraft "Mini -Mix " a miniature two -position mixer which- plugs directly into the microphone input of tape recorders and amplifiers, and the new "Tini-Jax" and "Tini- Plugs" which add greatly to the miniaturization of audio devices. 2C-1 Acoustic Research, Inc., 23 Mt. Auburn St., Cambridge, Mass., has recently published a new brochure on its "acoustic suspension" speaker system. Included is a brief explanation of the acoustic -suspension principle, performance curves on both frequency response and harmonic distortion, and model numbers and prices. The brochure will be mailed free on request. Z -S Astatic Corp., Dept. RC, Conneaut, Ohio, has compiled a new master cross -Index replacement chart covering all makes of phonograph cartridges which is available free to distributors and dealers. Consisting of eight letter -size pages, the chart lists not only Astatic cartridges, but those made by other manufacturers as well, together with their current Astatic replacement number. It is compiled in booklet form, with a three -hole punch for insertion into IF YOU ARE AN ELECTRICAL ENGINEER any standard loose -leaf binder. E -3 OR PHYSICIST. YOU CAN CONDUCT Radio Electric Service Co., 709 Arch St., Philadelphia 6, Pa., is making available at LABORATORY AND no charge a full -scale chassis layout which CLASSROOM PROGRAMS may be used as a template by anyone desiring to build a 60 -watt ultra -linear ON ADVANCED SYSTEMS IN THE FIELDS Williamson amplifier using the Acro TO- 330 output transformer and four KT66 OF RADAR FIRE CONTROL. ELECTRONIC tubes. A copy of the diagram will be COMPUTERS. AND MISSILES. mailed on request. Z-! Maintenance instruction GUIDED on an advanced Hughes Cornell- Dnbiller Electric Corporation, tire control system. South Plainfield, N. J., in a new eight -page illustrated booklet, describes in detail the J applications, uses and advantages of printed circuits in various electrical products, as well as technical information to aid in design or planning of printed circuitry. Titled "Printed Circuitry," the attractive two -color publication explains simply and authoritatively the different As a training At Hughes Research and Development types of base materials, laminate characteristics and circuit designs. Various engineer you will Laboratories in Southern California you, as an engineer chapters explain how to prepare master drawings, soldering techniques, and pric- become assigned to this program, will be a member of the ing variables. "Printed Circuitry" will be familiar mailed free on request. E-5 with the entire Technical Staff. Prior to instructing you Sun Radio & Electronics Co., Inc., 850 will receive technical training to become familiar Sixth Ave., New York 11, N. Y., has just systems involved, published an interesting 72 -page book with the latest Hughes equipment. under the title "Sun's 1955 Hi -Fi Facts." including the most Available at 35 cents per copy, the publication is a complete and comprehensive advanced electronic book with a large number of illustrations. Features included in the book include: computers. With this bow to construct speaker enclosures: the function and evaluation of high -fidelity advantage you will components; how to select a hi -fl system suited to the individual's needs, and a be ideally situated simple glossary of high -fidelity terms. Re- THE TIME WAS NEVER MORE OPPORTUNE quests for copy must be accompanied by to broaden your remittance. Z -8 THAN NOW FOR BECOMING ASSOCIATED experience Nsumade Products Corp., 250 W. 57th and WITH THE FIELD OF ADVANCED St., New York 19, N. Y., has issued a new catalog covering equipment for the stor- learning more ELECTRONICS. BECAUSE OF MILITARY age, tiling, shipping and editing of motion - picture film of all types. With the advent quickly for future EMPHASIS THIS IS THE MOST RAPIDLY of wide -screen projection and new developments in the television field, Neu - application to GROWING AND PROMISING SPHERE made has added well more than 150 new items to its 35- and 16 -mm accessory line, advanced electronics OF ENDEAVOR FOR THE YOUNG all of which are listed in the new catalog. Available on request. Z -q activity in either ELECTRICAL ENGINEER OR PHYSICIST. River Edge Industries, 5 River Edge the military or the Road, River Edge, N. J., in a new 20 -page catalog just released, illustrates and de- commercial field. scribes one of the country's most complete lines of equipment cabinets and speaker enclosures. The expanded River Edge line includes modern, traditional and provincial styling, with virtually all models available in a choice of eleven hand- rubbed HUGHES finishes. Also listed are a number of do -it- SCIENTIFIC AND yourself kits. Half -tone illustrations are RESEARCH AND DEVELOPMENT LABORATORIES augmented with line drawings which help ENGINEERING STAFF greatly in cabinet selection by showing the relative positions of compartments for Culver City, Los Angeles County, California tuner, amplifier, record player and speaker. Copy will be mailed free upon request. Z -8

AUDIO JUNE. 1955 5

www.americanradiohistory.com LETTERS FOR THE BEST Bird Deterrents IN MAGNETIC SIR : This may sound like another Audio Aud- ity* but it really answers the request of a RECORDING... reader for information. In the April issue, C. S. Clemens asks if ultrasonic frequencies can be employed for driving destructive birds from crops. Sad to say, most common birds seem to be oblivious to ultrasonics in doses that would be practial to cover large HALF -TRACK REDHEADS -first areas. Sufficient ultrasonic power to gen- choice of leading manufoctrers of erate heat in feathered or furred creatures may be a deterrent, but requires fantasti- home tape recorders. cally large powers. While lethal effects have been obtained in the laboratory at distances of several inches, the high absorption of ultrasonic sound in the atmosphere makes it improbable that this means can ever be used for bird riddance on the basis of heat generation or the flocculation of organs and tissues. This requires levels at the target of 160 to 200 db. Actually, the nervous system of common birds reacts to sound in the same frequency range as humans. Some years ago, the writer undertook to use ultrasonics at a reservoir infested by scavenger seagulls, but the project met with failure until the frequency range was reduced to the spectrum where human ears found it irritating, and the neighborhood indicated that drastic action might soon be taken to terminate the experiments. A more successful approach has recently been used by ornithologists where communi- cation is made with the birds in their own ornithic language. It has been discovered by Dr. Fring of Pennsylvania State Univer- sity that birds have a rudimentary language which consists of cries and shrieks and other warning sounds of danger, the presence of a natural enemy, food, and that they may have other signals necessary for their sur- vival and existence. The nature of these cries or signals varies with different species of birds. It has been shown that the distress cry of a seagull has no effect on the starling NEW! FULL -TRACK REDHEA and vice versa. These cries have been ...provide extended range, recorded and then analyzed in terms of their significance to the birds. For example, the designed for professional use. "danger" cry has been recorded and then played back to the birds on a later occasion with the result that they take flight and disperse, probably assuming that one of their scouts was giving a warning. Some of this work has been reported in the news- Look for the Redhead! papers and the scientific press. An organization headed by Dr. Miller Magnetic heads represent a small Brush Redheads use a specially McClintock of Scarsdale, New York, is of complete tape structure to now engaged in this activity, employing a fraction of the cost a designed laminated pole device known as "Bird -E-Vict." recording system. Yet, since these com- provide uniform track width. The pole SAUL J. WHITE, ponents record, reproduce or erase the tips are ground and lapped perfectly 82 Elm Street, magnetic pattern, their quality deter- flat to assure a precise finite gap. This New Rochelle. N. Y. mines the performance of the system results in faithful reproduction over an itself. That's why it's wise to choose In addition, High- Frequency Resonance in Pickups famous Brush Redheads. extended frequency range. Redheads are moisture- proof, non - SIR : curve in Fig. For professional recording purposes microphonic and provide high output. Mr. Preisman refers to the the Brush Redhead series now includes 4 of his article in the May issue as "satis- full -track heads. These heads provide For information on Brush's full line of factorily flat," although there is a 3 or 4 improved signal to noise ratio and single and multi - channel magnetic db resonance around 8000 cps. The strict heads, write Brush Electronics Com- requirements in design and manufacture of greater dynamic range. Separate full - of LP pany, Y -6, .3405 Perkins Avenue, pickups for proper reproduction vinyl track record, reproduce and erase heads Dept. pressings are not well known, but if the are available. Cleveland 14, Ohio. vertical stylus force is reduced to the recommended 3 or 4 grams, the peak at stylus resonance (mechanical) can attain an amplitude of 16 to 18 db, and it is probable BRUSH ELECTRONICS COMPANY that Mr. Preisman used a pickup which employed mechanical damping, which reduces INDUSTRIAL AND RESEARCH INSTRUMENTS the peak somewhat, along with the response PIEZOELECTRIC MATERIALS ACOUSTIC DEVICES Division of above the resonant frequency. MAGNETIC RECORDING EQUIPMENT AND COMPONENTS Clevile Corporation This type of resonance is one of the major ELECTRONICS (Continued on page 70)

6 AUDIO JUNE, 1955

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www.americanradiohistory.com to give a sense of direction is very old, and the first known example of two -channel sound reproduction is an experiment made fauttunt at the Paris Opera House in 1881 and described ih L'Ectricien of October 1st, 1881." He claimed that the beginning of the present development went back to 1929 when the Columbia Graphophone Company com- ?Lrttrr menced experiments two years before it joined forces with H.M.V. to form the present E.M.I. organization. "At that time ", he said, "it was realised that the use of headphones (although simplifying the technical problems to some extent) was im- practicable and that the mere substitution of two loudspeakers fed from two microphones spaced at ear distances was not RICHARD ARBIB° capable of producing the required result. "During normal listening the ear locates the sound source at frequencies below about the H.M.V. DEMONSTRATES STEREOSONIC as real 'two -ear' listening. Opening the 1000 cps by the difference of phase of TAPES other ear by bringing in a second channel sound wave reaching the two ears. The ear is like opening the other eye or the second which receives the sound in phase advance NEARLY A QUARTER OF A CENTURY AGO, lens and negative of a stereoscopic picture. indicates that the source is towards that the then Master of the King's Musick, The re- created sounds immediately leap into side of the head. The amount of phase dif- the late Edward Elgar, conducted ference will indicate the degree in which Sir life and movement ; they acquire breadth a symphony orchestra in a building which and depth and solidity, so that you can hear the sound source is off centre. Whether the had just been erected in the gardens of an all round them, just as you can see all round sound source is in front of or behind the Edwardian house in London's fashionable the objects in a stereoscopic picture. No listener is indicated when he automatically St. John's Wood, which is just about 2 longer does the music of an orchestra, a moves his head. If turning the head, say miles from the West End of Britain's capi- choir, or a dance band appear to be static to the left, makes the sound in the left tal. and funnelled through a loudspeaker aper- ear appear louder, then the source is behind The leading members of the British Press the listener. If, however, the sound de- ture ; it has all the character of being spread and technical experts were present on that out across the width and depth of the stage, creases or remains constant in the left ear occasion which was a landmark in the de- with the instruments and voices in their and rises in the right ear, then the source velopment of recording for it was the open- correct perspectives. A grand piano no of sound is in front. ing of what was then claimed to be the longer 'sounds like a piano;' it IS a grand "At frequencies higher than 1000 cps. largest gramophone recording studios in the piano possessing breadth and depth and a where the dimensions of the human head World which had been built specifically for full- length keyboard with the bass and act as a shield, the ear depends more on that purpose. Since that time, nearly 25 treble node. at either end of it" the difference of level of the sound reaching years ago, the majority of the World's the two cars, the sound source being on greatest artistes have made recordings for Two -Channel Reproduction in 1881 that side of the head on which the sound posterity in the three studios which have, After his introductory remarks, H. A. M. appears louder to the ear. For steady for nearly all that time, been occupied by Clark, Technical Manager of the Record sounds, phase difference is often too am- the E.M.I. Company whose records are Division of E.M.I. gave some technical in- biguous at the higher frequencies, time of marketed in England under His Master's formation concerning the history of two - arrival is a very critical test of direction. Voice, Columbia, Parlophone, Regal, and channel recording and the developments "In 1929, the late A. D. Blumlein realised M.G.M. trade marks and in the U.S.A. that have been made recently by H.M.V. that it was necessary to convert the outputs now under the R.C.A. Victor and Angel He said "The idea of reproducing sound at of the two microphones into two different marks. a distance in such a way that the listener sorts of outputs having the correct ampli- A few weeks ago a further landmark was can use the natural function of the two ears tude differences for feeding the loudspeak- made in recording history, when one of Britain's greatest conductors, Sir Malcolm Sargent, introduced to a gathering of the Press and sound experts, H.M.V. Stereo- sonic tapes. Sir Malcolm said "This is the one fundamental development in sound recording and reproduction which musicians have been awaiting for years." Sir Mal- colm, who has followed with keen interest the recent work on this subject and has co- operated enthusiastically in making special recordings for the demonstration pro- gramme, emphasized his point by saying that even the very high degree of realism now obtainable from modern tape and microgroove records on good equipment has necessarily been "flat ;" the sound has been in one plane, as it were. This was inevitable so long as recording and reproduction were confined to one channel-like listening with one ear or looking with one eye. "If you close one eye and look around you" continued Sir Malcolm, "objects appear flat and in one plane, like an ordinary photograph taken with one lens on one negative. Look at a stereoscopic pl ture- taken with two lenses on two negatives- and the photograph imediately comes startlingly to life, with every detail standing out clear and sharp in solid three- dimen- sional realism. So it is with single channel recording and reproduction. Good though this is today -and at its best it can be very, very good, it can never be quite as natural W. S. Barrel) (left), manager of EMI recording studios, talking to two of the members of the Record Div.sion largely responsible for the technical development of the new Stereosonic sys- * Multitore Solders, Ltd., Hemd Hemp- tem -Dr. G. F. Dutton of Advanced Developments Section (center) and H. A. M. Clark, Tech- stead. Herts., England. nical Manager.

8 AUDIO JUNE, 1955

www.americanradiohistory.com "SCOTCH" Brand's new thin groove reel prevents tape tangles!

NO MORE "ZIG-ZAG" WIND to tangle tape! "SCOTCH" Brand has come up with a sure way to make magnetïc tape wind smoother Write on it! and reduce side play to a minimum. It's "SCOTCH" Brand's new, 10% " professional reel. Made from glass- reinforced plastic, the new reel measures just .270" wide ... 75 mils thinner between flanges than older type aluminum reels. Offers plenty of other advantages, too! "SCOTCH" Brand's reel spins true because of Won't dent... %6" center hole conforming to RETMA specifications. Won't dent or warp, thanks to tough fiber glass won't warp! reinforcement. And you can write on it for identification. All these features, plus exclusive slot threading -at no increase in cost.

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AUDIO JUNE, 1955 9

www.americanradiohistory.com ers. In this way, the effective time of ar- "The system requires two independent rival of the sound at the two ears could be channels from the recording studio to the made to simulate what happens in natural listener. In practice, the two channels are hearing, even though each ear could hear put on two tracks on a % -in. magnetic tape both loudspeakers. While this effect could and replayed through two identical sets of be approximated by the use of widely amplifiers feeding two loudspeakers. The spaced microphones, improved methods are spacing of these two loudspeakers will vary now available whereby the two microphones according to the size of the room and they can be placed in close proximity and still will generally be heard to best advantage achieve the required outputs to the loud- when placed in the corners at each end of speakers. In this sense the new system is one wall of the room, so that the subtended comparable to a single microphone tech- angle to the listener is between 60 and 90 nique- resulting in a simplification of the deg." problems of studio balance and acoustics. The audience was then treated to a "In 1933, the E.M.I. Recording Research demonstration of stereosonic recordings of Department successfully made a single which the first item was the Philharmonia groove record containing both recording Orchestra conducted by Sir Malcolm Sar- channels by using a complex cut involving gent, playing a Tchaikovsky Suite. The re- both lateral and "hill and dale" recording. production sounded spacious and realistic .21 When, however, this method was applied but from the rear of the studio it was not to modern LP records, it was found to be particularly apparent that some of the in- very difficult to achieve the high standard struments of the Orchestra were grouped of reproduction quality associated with sin- on the left, whilst others were on the right. gle- channel disc recordings. Magnetic tape, Although the sound did not come from simplify however, offered a recording and repro- a "funnel" as described by Sir Malcolm ducing- medium which was inherently free Sargent, one had the feeling that the sound from many of the disadvantages of discs, came from the centre of the studio some- custom and attention was therefore concentrated on what as one would have heard from an this field, with its promise of quicker and orchestra present in it. The next item was more effective results. a reproduction of Brahms pianoforte solo FILTER by Malcuzynski. The effect here was not Difference Between H.M.V. and other convincing. Although the quality of repro- installation 2- Channel Systems duction was of the highest order, the reproduction was too loud and the piano did not "The Stereosonic system differs H.M.V. natural. The third item was, however, from most other systems that have been sound remarkable. An excerpt from the Fi- tried by the fact that the stereophonic effect truly nale of Act 4 of "The Marriage of Figaro" is operative over the whole frequency range. was reproduced from a stereosonic tape, systems have been demonstrated for Other made by members of the Sadler's Wells has been quite erroneously claimed which it Opera Company and Orchestra. The effect that it is not necessary to reproduce the The 4200 Variable Filter and 4201 of movement from side to side of the studio below about 500 cps. It Program Equalizer are now available stereophonic effect was immediately apparent, and the whole has, however, been found by H.M.V. engi- in component form, as illustrated, for reproduction of both the voices and the Or- boominess is one of the greatest the custom builder. neers that chestra was most natural. The fourth item difficulties in sound recording and repro- In addition to the flexibility of was a reproduction of a dance orchestra. duction, and that this boominess is due to installation, all the features and char- obvious that once again H.M.V. lack of stereophonic definition in the low It was acteristics of the standard models are had tried to establish their claim to be first frequencies. This definition is fully restored retained. in the field by giving a demonstration of a in the new "Stereosonic" system so that a The high and low sections of either new development before being in a position bass drum sounds like a bass drum and not model may be obtained separately. to satisfy public demand for their new prod- like a door banging, and one can discrimi- Complete wiring instructions included. uct. they did show the equipment nate between the original sound of the dou- Whilst for the reproduction of stereosonic tapes Send for Bulletin 7'B -3 ble bass, for instance, and the reverberation of this sound in the studio. (Continued on rage 77)

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10 AUDIO JUNE, 1955

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AUDIO JUNE, 1955 11

www.americanradiohistory.com EDITOR'S REPORT

JUDGE FOR YOURSELF H. R. 2128

O. r rHINC that practically all products have in com- Across our desk this past week came a letter from one mon-be they hi -fi, groceries, or garden tools -is of our regular correspondents who lives by his wits (no the continual struggle to convince the potential offense intended -he is actually an inventor with an im- purchaser that each is better than its competitors. This pressive list of patents to his credit and, more important, is a natural and healthy condition, and it makes for im- an equally impressive amount of real estate to show how provement in the finished products from day to day and useful his inventions were) which seems rather more im- year to year in order for each manufacturer to maintain portant than most letters which appear in the LETTERS his position in his particular field. column. This correspondent, Benjamin F. Miessner, Every manufacturer extols the virtues of his own calls our attention to a bill now pending before the House product -carefully stressing the features that are ob- of Representatives Judiciary Committee-H. R. 2128. viously and noticeably superior to his competitors' goods. This is a bill which provides for the extension of those and equally carefully placing a minimum of emphasis on patents which could not be promoted, developed, or those points that are not "tops" in their field. We are worked in manufacture because of the restrictions on often asked for an opinion as to what is the best loud- manpower and strategic materials imposed by the gov- speaker, best enclosure, best pickup, best amplifier, and ernment during the war years. so on, and our answer is invariably the same -the one The idea of providing some relief for the inventor who you like best. was unable to derive income from his brainchild over a Fortunately, the equipment offered in the high fidelity reasonable time, which is normally related to the statu- field is almost uniformly excellent. True, one loud- tory period of seventeen years, is not new. Such legisla- speaker may sound differeñt from another, but that is tion is already in effect in the United States for war

easily explainable. Presumably, every loudspeaker manu- veterans, and most other , patent- recognizing countries facturer does his best to produce a unit which reproduces have already made some provision for relief to inventors music as perfectly as possible-or if he doesn't, he who were prevented by circumstances beyond their con- should be trying to-but since there are no accurate trol from working their inventions. It seems only fair to means for evaluating the subjective effect of loudspeak- extend the life of patents in those instances where re- ers, the judgement of quality must come from an in- strictions caused the inventor to suffer loss of income dividual, or a group of individuals. Thus, if A builds the that he would normally have had. best loudspeaker he knows how to, and B makes the best Not everyone has a definite interest in patents, for one he knows how to, and so on with C, D, and E, yet there are many millions whose work does not lead them all sound different, no one can truly say that one is better in the paths of inventive opportunity. But the average than the other. One listener prefers the first one, another experimenter-whether in audio, plastics, or toxicology the second, and so on, and the success or failure of each -is quite likely to have a patentable idea at some time manufacturer depends on what percentage of the market in his work, and would welcome a fair shake. By writing he can best satisfy. And so it goes with all components- our congressmen, we may just possibly be safeguarding not just loudspeakers alone. Even amplifiers may meas- our financial future. Aside from the fact that it is only ure exactly the dame by measurement techniques we right that the inventive minded-who have had such a know about, and yet sound'different. The point is that all large part in our economic development -should not be the hi -fi manufacturers are specialists, and that they all penalized for something which was not of their doing. make an honest effort to build the best products they can \Vho knows -maybe any one of us will be in those shoes Such is not always the case with some of the pseudo - some day ? hi-fi products that are offered in competition to audio A letter to your congressman would help -and re- components. To be sure, the same claims are made in member the bill, H. R. 2128. We should all be in favor the advertising -or more generally even superior per- of its enactment, and soon. formance is claimed. This is unfortunate for the great mass of people who are not yet familiar with the quality NEXT MONTH with which hi -fi components are normally associated, Some ago October, to be exact -we pub- And in months -last for they do not know where to go to compare. article describing briefly a unique loudspeaker are not demon- lished an most instances, quality audio components which was somewhat revolutionary in construction. We strated in the same room with these so- called superior had hoped to present more information about this unit products -because they aren't sold by the same stores - before now, because of the large response from the read- so it is difficult to make direct comparisons. The audio- ership. In fact, we even went so far as to schedule Mr. fan knows why they aren't demonstrated together, too. Villchur's description of its testing and performance in So, to sum up our opinions and recommendations, we this issue. However, the size of the phonograph equip- say, "Judge for Yourself." Hear them all, to be sure, but ment section- herein- reduced the available space in make sure that you judge on the basis of sound quality the rest of the issue, and we had to leave it out. Look for after adequate comparison. And judge on the basis of it, however, in the July issue, along with many more performance rather than claims. interesting articles.

12 AUDIO JUNE, 1955

www.americanradiohistory.com No dead spots No hot spots

Par fa/ view oì COP installa5on at modern Linron Fields Race Track, rxated

just sot" d Chicago at Cete, . Pinois

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Outdoors or incoors, everyone can comfortably hear everything when you use the C DP. Listeners off the axis, where the majority of audiences are, do not have to strain to hear, while those on the axis are not assaulted by blasts of sound. The CDP provides anooth peak -free wide- range response, with 120° sound distribution at all frequencies up to 10,000 cps. Unit energy is far more efficient- there's no wasted power. You can do a better job with fewer units at less cost. CDP utilizes two coaxially mounted diffraction horns, working from both sides of a single diaphragm, plus optical slit diffraction for smooth sound dispersion. CDP delivers 254 octaves more musical range than comparative units. Molded of glass fibers, CDP is weather-proof, blast- proof, splash- proof. Compare the CDP with any other unit in the environment in which it actually will be used -in the field or in an auditorium. Prove to yourself Elect,o -Voice CDP Public Address Loud- why it is so superior, why it is the best value ever! speaker System was chosen for the 8,248 seat North Side Gym, Elkhart, !adiaaa, one of the 'Pat. 0169904 and Pat. Pend. nat;on's 'argent high school gyms. Cluster of stacked CDP's can 5e seer. :a photo taken during construction. NO FINER CHOICE THAV I

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AUDIO JUNE, -955 13

www.americanradiohistory.com Hundreds of thousands of telephone conversations or hundreds of television programs may one day travel together from city to city through round waveguides - hollow pipes - pioneered at Bell Telephone Laboratories. Round waveguides offer tremendous possibilities in the Pipes endless search for new ways to send many voices great distances, simultaneously, and at low cost. Today, Bell Labora- tories developments such as radio relay, coaxial cable and multivoice wire circuits are ample for America's needs. But of tomorrow's demands may well call for the even greater capacity of round waveguides. Unlike wires or coaxial, these pipes have the unique property of diminishing power losses as frequencies rise. Progress This means that higher frequencies can be used. As the frequency band widens, it makes room for many more voices and television programs. And the voices will be true, the pictures faithfully transmitted. These studies illustrate once more how Bell Telephone Laboratories scientists look ahead. They make sure that America's telephone service will always meet America's needs, at the lowest possible cost.

New type of waveguide pipe formed of tightly wound insulated wire transmits better around corners than solid-wall pipes.

New type waveguide is bent on wooden forms for study of effect Testing round waveguides at Bell Telephone Luboratorie,. Holmdel, New Jersey. of curvature on transmission. The I alike coaxial cable, waveguides have no central conductor. Theoretically, waveguide itself is here covered nice- capacity is much greater than in coaxial cable. with a protective coating.

Bell Telephone Laboratories Improving America's telephone service provides careers for creative men in scientific and technical fields.

www.americanradiohistory.com A High -Power Amplifier With Minimum Distortion

BRUCE DePALMA

In an amplifier not for construction by the novice, the author tries for a new "ultimate" in performance.

THERE IS NO DOUBT that the best of (4) A negligible incremental output input cathode). Each stage must operate present - day amplifiers conform to impedance, and a means for making at as low a level as possible, which can- very high standards. However, a this variable in the negative direction. not be achieved easily with internal feed- study of the problem of distortion indi- (5) Complete freedom from hum. back loops. A minimum number of stages cates that still higher standards can be hiss, and microphonics. is used, and the circuitry kept simple. set for a distortion -free amplifier and For the lowest distortion, any ampli- Incidentally, no matched components the writer has evolved a design whose fier must be critically adjusted. There- need be used. principal constructional feature is a new fore, for the best results, it is recom- The input stage (Fig. 1) is a triode cross -coupled phase -splitter- driver. mended that the construction of the whose circuit parameters have been ex- In on working the new design the amplifier to be described should not be perimentally adjusted to produce the writer realized that a somewhat new ap- lowest amount of intermodulation with- proach attempted by those who do not have was necessary. To begin with, access to at least an intermodulation out feedback. This drives a modified the new circuit would have to satisfy analyzer, a vacuum -tube voltmeter and cross -coupled phase -splitter- driver V-- these requirements: a good oscilloscope. Vs-174. This new splitter-driver circuit is primarily responsible for the perform- (1) Negligible distortion - inter - modulation, harmonic, phase and fre- The Circuit ance of the amplifier. In the original cross- coupled phase quency. The basic philosophy inherent in the (2) No tendencies toward low -fre- splitterl there were two cathode follow- design was to make the amplifier as ers driving two triode voltage amplifiers. quency or ultrasonic oscillations. perfect as possible before the application (3) A maximum power rating far For single -ended inputs the grid of one of negative feedback, so that with its of the cathode followers was grounded in excess of that required for the re- application the distortion would virtu- production of the highest instantane- and left unused. It was found that the ally vanish. The signal level inside the unused cathode follower could be re- ous peaks found in music. amplifier was to be kept at the lowest possible level to keep the distortion at 1J. N. Van Scoyoc, "A cross -coupled in- * East Campus, Massachusetts Institute a minimum. In order to realize this only put and phase inverter circuit," Radio of Technology, 3 Ames St., Cambridge 39, one voltage feedback loop is used (from Electronic Engineering Edition, Radio & Mass. the output transformer secondary to the Television News, Nov. 1948.

X 510 B+ 220VAC CERAMIC BL 56VDC Mv 10 MEG 600V V7 KT-66 AGROSOUND Vi 0.47 V3 KT-56 V5 V2 365 V DC T0 -330 1/2 6SL7 u I/26SN7 EFP 60 1000 GR Ñ 20 2VAG I 450 o - ¡V INPUT 1- î 271/2V AC 1.0 16 ft. 200V 13.5VDC CER- ò 300 100 V 68VDC 1.25VAC -15V 01 AMIC ...IEyDISC DC 0 3 RD 20VAC 0 820 15VDC eFt w° z 0ó RD A t13VAC ó% L ó 4n el b o 01 IA 4w 3-30 put u o CERAMIC DISC TRIMMER = 2 Cu f n (DAMP-1_ Ó ING GR 17,500,10W 1000 Y ~_ óm WII KT-66 V6 VB KT-66 o i 3 3 3 ó 470 yyf, 1500 V CERAMIC BL 00 500 ó WH 0 AC BALANCE 0.0 10-1311Y 4 MY b 550 V DC RECTIFIER

K X 8 600v1 600V1 700V1 8+ V4 EFP-60 1.0= 600V

Fig. 1. Circuit diagram of the author's amplifier. Intermodulation and harmonic distortion are at lower than inaudible levels at 50 watts output. The EFP -60's are new, use a special 9 -pin socket.

AUDIO JUNE, 1955 15

www.americanradiohistory.com mhos. Using this tube, one can use a very low value of plate -load resistor, thereby keeping the driving impedance low, and still obtain a very high gain. In the splitter- driver circuit, the tubes Fig. 2. Amplifier and have a gain of better than 250 with a power supply are to- 16,000 -ohm plate load resistor. Their gether on the 13.' circuit parameters have also been experi- 17 3 -inch alumi- mentally adjusted for lowest distortion. num chassis. Steel Naturally, using such high -gain tubes might be a better presents some problems of input- output chassis material if isolation and shielding, but by the unit is to be careful handled to any ex- construction one will have no trouble tent. if the usual precautions adopted when working with high -gain, wideband amplifiers are observed. A 60,000 -ohm variable resistor across the high -voltage supply furnishes the "negative current" (a term adopted by the manufacturer) for placed with a resistor equal to twice the high the secondary are they are approximately equal. cathode of the EFP-60. tube's nominal plate resistance with no There is One electron one difference, however. Since impinging on this secondary cathode effect at all upon the operation of the the source is in series with the load in knocks 5 circuit except a slight additional amount the grounded out more. These electrons are -grid stage, the tube has to supplied from ground, while the elec- of degeneration. This further helps to deliver power. On the other hand, with keep the circuit insensitive to the effects the grounded- trode is kept at about 200 volts' above cathode stage, the input ground by the B+ supply. This means of drift and tube aging. This unused tri- driving impedance is almost infinite for ode might then be used for the input low that the resistor slider is kept close to frequencies. The cathode follower its grounded voltage amplifier. However, tubes which which drives these end. A ceramic disc capac- two stages has a low itor bypasses the secondary cathodes to make good low- distortion cathode fol- output impedance, but in order to get the ground ; lowers in the cross -coupled circuit do least amount at the sockets of the EFP -60's of degeneration from the this helps to stabilize not make good high -gain, low- distortion cathode follower the stage. In this this output impedance circuit the suppressors of -60's voltage amplifiers. Therefore, two sep- cannot be the EFP reduced low enough to match are connected to ground instead of to arate tubes were used : one -half of a the input impedance 'of the grounded - their cathodes. was found 6SL7 for the voltage amplifier and one - grid It that when stage without drastically reducing they were connected to the cathodes half of a 6SN7 for the cathode follower. the gain of the whole splitter.4 There- The other halves of these tubes un- distortion and parasitic oscillations re- are fore, in order to get any gain out of sulted. The used and are thus free for other purposes the circuit fact that they are about 15 there has to be a mismatch volts negative with respect to the cath- such as a preamplifier. between the cathode follower and the Contrary to popular belief, a odes has no effect on the operation of cross - grounded -grid stage, with consequent the tubes. coupled circuit is not self balancing, and unbalance of drive to the two stages. the so- called balance controls incorpo- To adjust the drives to the final tubes rated in these circuits accomplish noth- for lowest over -all distortion a method The Power Stage ing but to change the d.c. biases on the had to be devised to vary the drives to The output stage is a conventional voltage -amplifier tubes. Alternating-cur - the grounded -grid and grounded-cathode push -pull -parallel one with KT -66's ul- rent balance can be accomplished by stages of the splitter. To see how this tralinear- connected, using the Acrosound adjustment of this control to extreme was accomplished refer to Fig. 1 and ' TO -330 transformer. A 300 -µµf capac- values, thereby changing the mu of the note the 500-ohm potentiometer in series itor and shunt .01 -µf ceramic disc by- tubes. This practice naturally leads to with the cathode -bias resistor of V. The pass the final cathodes to ground. It is increased distortion. It must be realized arm of this potentiometer is connected essential to use this much capacitance that the drives to the power tubes are to the grid of V. Part of the negative to keep high -level intermodulation at a not necessarily equal to each other at feedback applied to V, is developed minimum. The disc capacitor nullifies the point of lowest distortion. Final tube across the cathode resistor of Vi. By the effects of inductance in the large unbalance and transformer unbalance, varying the amount of degeneration ap- electrolytics, thereby providing adequate negligible in high -quality output trans- plied to the Y, grid (by tapping down bypassing over the entire useful fre- formers, account for this phenomenon. on the V. cathode resistor) we can equal- quency spectrum. When final -tube and transformer unbal- ize the loss of drive to the upper tube due A 470 -µµf high -voltage ceramic ca- ance cancel out the inverter unbalance, to its mismatch. With this control, the pacitor from the blue -white plate lead low distortion results, but this is not a.c. balance of the inverter can be varied of the output transformer to ground always the case. about 10 per cent either way -enough corrects for a capacitive unbalance to Unbalance in the cross -coupled circuit to take care of any final-tube or trans- ground which would otherwise exist in can be traced to the driving of one tube former unbalance. Adjustment of this the transformer due to the geometry of by its cathode and the driving of the control affects the d.c. balance of the the windings. This capacitor clears up other by its grid. Assuming for the mo- inverter slightly, necessitating readjust- a slight ultrasonic parasitic which de- ment the absence of negative feedback ment of the 2000 -ohm d.c.- balance poten- veloped when the transformer was over- (about 21 db of current feedback in the tiometer. loaded. The measured capacitive un- writer's circuit) the cross-coupled split - In order to comply with the original balance existing in the transformer is ter reduces to a grounded -grid and a requirements of a minimum number of actually less than 100 µµf. The 470 -µµf grounded- cathode amplifier driven by a stages and of keeping the a.c. voltages capacitor evidently has some other sta- cathode follower. In a grounded-grid inside the amplifier small, a new tube bilizing effect than just cleaning up the stage the gain is equal to µ + 1. In the just recently placed on the market, the capacitive unbalance to ground. grounded-cathode stage the gain is just EFP-60* was used as the voltage-ampli- µ.Y8 When the gains of these two tubes fier -driver in the cross -coupled stage. * The EFP -60 tubes are manufactured in This tube utilizes the principle of sec- the Netherlands by N. V. Philips Gloei- ' F. E. Terman, "Radio Engineers Hand- ondary emission to obtain the extremely lampenfabrieken, Eindhoven, and are im- book," 1st ed., McGraw-Hill, New York, high transconductance of 25,000 micro- ported into the U.S.A. by Amperex. Usually 1943, pp. 470 -471. stocked by the larger parts houses, they may "Reference Data for Radio Engineers," S. W. Amos "Valves with resistive be ordered from Amperex, Hicksville, N. Y. 3rd ed., Federal Telephone and Telegraph loads," Wireless Engineer, April, 1949, pp. if unavailable in your locality. The socket Corporation, 1949, pp. 252-253. 119-123. is Amperex No. S- 13211.

16 AUDIO JUNE, 1955

www.americanradiohistory.com The negative feedback voltage is taken duced sounds to have a muddy, mushy, from the 4 -ohm tap on the transformer lack-of- definition quality. These difficul- secondary. It was found experimentally ties are completely absent with the am- that in this way more feedback could be plifier discussed here. applied without instability (high -fre- At extreme high frequencies, the large quency oscillation) than could be applied amount of feedback employed tends to when the feedback was taken from the - introduce problems. Since more than the 16-ohm tap, the conventional practice. 30 -db limit recommended for the trans- The negative feedback is applied to the former is being applied, it is natural to cathode of the 6SL7 voltage amplifier expect some difficulties to develop. In V, through a phase -advance network this amplifier two unstable regions were consisting of a 3- 30 -P-of trimmer capac- found -regions where the phase lag of itor in shunt with a 24,000 -ohm resistor. the amplifier was sufficient to cause it The amplifier has a voltage gain of about to oscillate through the feedback loop. 535 from the input to the grids of the These were 110 kc and about 1.5 mc. KT -66's with no feedback. 32 db of nega- The instability at 1.5 mc. was elimi- tive feedback is applied in one loop from nated by reducing the loop gain at this Fig. 4. Fuzzy tips on the input- output charac- the output to the input. With this amount teristic shown in this oscillogram denote in- frequency to a value less than unity, stability at of degeneration, 2 volts at the input extreme high frequencies at very shunting the 470,000-ohm plate load re- high power levels. Adjust the feedback trim- drives the amplifier to 50 watts output, sistor of V, with a 5 -ttt+f ceramic cape; mer to eliminate this trouble. so that there is a voltage gain of about itor. This expedient did not work, how- 10 to the 8 -ohm tap on the output trans- ever, for the 110 kc oscillation. It was minum chassis. It is recommended that former secondary. found that the output transformer leak- the amplifier be laid out and constructed Since the feedback loop includes the age reactance was causing sufficient in straight -line fashion. Particular at- output transformer, it is natural to ex- phase delay at this frequency to prevent tention should be paid to common stage pect stability problems to arise. The am- 32 db of stable feedback. Various "step" grounds and bypassing the EFP -60 plifier is perfectly stable at the low - selective phase- advance networks were dynodes to ground directly at the socket. frequency end, due to the large ratio tried in order to steer the phase charac- Radio -frequency wiring practices are (greater than 400 to 1) of the coupling teristic of the amplifier away from the advisable. It is recommended that the capacitor low frequency cutoffs.5 There 180 -deg. point in this region. None of filament leads be shielded or twisted and is however another low- frequency cutoff, these "step" networks had much effect, kept close to the chassis. All signal wir- that of the transformer. Its effect on so a variable 3- 30 -1+1f mica trimmer ing should be point-to -point and kept the low- frequency stability is hard to across the feedback resistor was finally away from the chassis. In particular, the ascertain because it varies with the level adopted. This expedient cured the oscil- 1 -µf coupling capacitors should be sus- of transformer excitation. Suffice to say lation. pended away from the chassis by their no low -frequency peak was found in the An adjustable incremental damping pigtail leads. It is definitely not recom- range ending at 1 cps. Due to the diffi- factor network has been incorporated mended that bathtub capacitors be used culty of making measurements, the re- into the design of the amplifier. The op- for this purpose. The writer suggests gion below 1 cps was not investigated. eration of this network is to control the metallized-paper tubular capacitors for The long time constants used in the am- amount of negative feedback applied their small size, high voltage rating and plifier reduce the low- frequency phase to the amplifier by means of the current self -healing properties. Only noninduc- shift to almost zero, while extending the flowing in the load. The adjustment of tive composition resistors should be used low- frequency response of the amplifier the 1 -ohm potentiometer is conven- for the grid and plate stoppers of the to below 1 cps. This extended response tional.6 If not desired, this network can KT -66's, and these should be connected is obtained without the low- frequency be eliminated without affecting the per- by the shortest leads directly to the transient instability peculiar to William- formance of the amplifier in the slightest. sockets. The KT -66's should be allowed son -type amplifiers. Many of these am- plenty of ventilation, as they must be plifiers are in a condition of near oscil- Construction run at maximum ratings for lowest dis- lation at a frequency of about 2 cps and tortion. The filament supply for The amplifier the when the amplifier is excited by a low - and power supply, il- amplifier must be the correct 6.3 volts; frequency peak, it is "triggered" at this lustrated in Figs. 2 and 3, were con- the EFP -60's are very sensitive structed to devia- subsonic frequency, causing the repro- on the same 13 x 17 x 3 -in. alu- tions in filament supply voltage, especially in the negative direction. The plate 6 N. H. Crowhurst "Feedback," "Audio 6 "A new approach to loudspeaker damp- supply Handbook No. should be able to deliver a con- 2," Norman Price, Ltd.. ing," Warner Clements, AUDIO ENGINEER- tinuous 300 ma at 1952. ING, August, 1951. 550 volts with good regulation. A pair of 5V4's as rectifiers is recommended. Although the manufacturer's recommended maximum plate voltage per plate is exceeded, no trouble has been experienced in several months of extended operation. It was found that the better regulation inherent with 5V4's will reduce the high -output -level inter - modulation by a factor of more than 25 per cent over a pair of 5R4GY's. Fig. 3. Under the chassis of the ampli- Adjustment fier. Despite experimental nature of this Perfection is no accident ; distortion - model the important free operation cannot be achieved with- leads are dressed as out critical adjustment. the author recom- After checking the wiring mends the follow- in the text. ing adjustments are made with the power off : Set the d.c. balance control to its middle position, the arm of the a.c. balance potentiometer close to the junction of the 15,000 -ohm and 510-ohm resistors, and the slider on the 60,000 -ohm resistor to the grounded position. Adjust (Continued on page 75)

AUDIO JUNE, 1955 17

www.americanradiohistory.com At Home with RU Io LEWIS C. STONE

Homework Hi -Fi

Wherein informal audio -pile yields precision audio results

AS FAR AS we can tell this month's hi -fi system points are, so to speak, pictorially sited together in intimate con- to no particular trend in "variations on the theme of tiguity as of houses in, say, an Italian mountainside village. housing the equipment," which is one of the topics on The arrangement, in fact, places what is in this case the this department's agenda. Are there more hi -fi installations most used article-the tape recorder -above the comfortable contained in music -wall erections than are cabineted sepa- height for handling (which should be, as broached in this rately (and we've had both here), or housed in a "projection department last year, on a level with your bent elbow, neither room" (of which more another time, perhaps) ?-we have much lower nor much higher). But let us observe the ameni- no way of stating authoritatively. The fact is, these varia- ties of open -mindedness and hold ourselves to a quite "linear" tions are seemingly endless as between one hi -fier and an- reaction to this departure from the rules of operational con- other. We have found that equipment housings are either venience. For, though our audiophile's audio -pile may run completely deceptive or disarmingly revealing (reflection, if counter to the tenets of the counter -top school of hi -fi com- any, on their owners' character not intended). How a few ponent concealment, we shall have to concede that reader such installations have been managed will be presented in Crofford's array of cases and cabinets holds more than we all their grisly detail in succeeding editions. Space permit- would ordinarily permit the first casual, jaundiced glance of ting, we expect some of these will be in the form of replies, our interior -decoration indoctrinated eye to perceive. See the to direct inquiries we have been getting from readers of this block diagram, Fig. 2. corner of Audio. (Corresponders please note.) Yet it is not for want of manual skills nor for lack of desire that this system is relatively "unhoused "-as a system. Audiophile's Audio -Pile On the contrary, our reader is far from being unhandy with a tool -even those carpentering ones we listed rather copi- The home audio system we have taken on for discussion of limited spare big rigs of ously in our opening article. But in the use now is in essence the not so little brother to the be profligate with devotion to the Like these, reader Crof- time he has preferred to the professional recording studios. cult of the cabled wire -up, the reamed -out cut -out for socket, is recording technician with Westminster Re- ford (who a transformer and so on, that go with making chassis build- cording Co. Inc.) shows thoroughbred tape recording and amplifier preamplifier, am- ups for (you've guessed it) that certain U- L- playback equipment; plus of course tuner, the expense, up to now, of any working earphones, microphones, disc playback. circuit adaptation at plifier, power supply, in homogenized cabinetry. It so happens that this hi -fi installation spreads itself with in Fig. 1). They some nonchalance in its several "arks" (as Home On the (Frequency) Range 235 E. 22nd St., New York 10, N. Y. For this man's money, hi -fi can easily be forever. His

shows main speaker system; Ampex electronics assembly in Fig 1 (left). No wallflowers are these vociferous hi -fi furnishings. Line -up Klipschorn phono cose over separate speaker for TV, with mechanical assembly in case atop TV cabinet. At right is Marantz Audio Consolette over and radio cabinet which also houses main power amplifier. Below it is the REL Precedent FM tuner. Fig. 2 (right). Chassis of amplifier and separate power supply in pre -tube- mounting stage. Tube sockets are Vectors: wiring on underside is cabled; transformers are completely potted.

www.americanradiohistory.com audio life is rounded out with what could be (we daresay) every man's dream -a library of many hundreds of across - the- labels LP recordings of all shades of musical thought, not to mention a solid collection of original and facsimile large -reel tape -ups in total beyond the reach of most of us financially, and anyway for most of us -whose hi -fi is a hobby marginal to our daily breadwinning- regrettably unavailable. In his view the playback equipment, thoroughbred though it surely is, should be regarded as valet and handy- man to this nobility of the world of recorded music. Which may go a little towards explaining (there are other reasons, of which later) why the walls of this man's audio room are also played down by being painted, if not an absolute black, then the closest thing to it we have ever "sensed." Moreover, three of the cabinets are ebon ( "ebony" is just not the word for it). Another, the speaker cabinet, is blond ; but black again is the portable case in which the tape recorder is mounted. Add low -key lighting (photographing the joint was quite a problem at first), dark drapes, dark upholstery -and one could pretty well imagine (sans the incense burner routine) a Baudelaire -ish world -well -lost emanation -perhaps, for all one can tell, a fitting setting for a sort of audio - séance kind of place. The total effect touches on space without limit, for in this dark nimbus little depth of field can be managed by the eye. But as for the ear-there's an organ gets the red (black !) carpet rolled out. Fig. 3 (above). Block schematic of the entire The vortex of sound system as this reader uses it. Important is is held in fact by the dark embrace of the somber walls, at it of flexibility and convenience. Fig. 4 (below). were, and it might be damped or extinguished but for the Schematic of the unusual 60 -watt amplifier and clear assertiveness of the highly efficient speaker system, power supply. Note use of voltage regulation in which leaves no wave or impulse without its due measure of circuit of latter. See parts list for components. reporting. Housed in the tallest single cabinet (nearly five feet high) is this speaker system. The main unit is the whopping 18-

6527 GTA V6 0B -2 C4-.5 5692 30=ce - á ó V2A ó T1 C71 < n - Ica N. C2-.25 2 F- 30 _ é 30 V3A ó L 01 `._. , I0O ppf R122200 o R16 0 r O 25,000 8 R2 T o R17 1 °w R20 °-- 25 000 } f 10,000 VIA ú 27,000 04 o C6 i`%, ó e 68 - o ppt ,V3B .-1 GND V28 se a V5 6550 05-.5 Hr *MATCHED VALUES

13 T4 R28-22 R29- 3300 N t « 6.3V,10A ALL FILS SRI 6.3 V 117V TNO/ R35-1000 L120H,rr1 50 t' 300MA -

5V,6A C12 -TC 13 R32 47 16 I 32 V9 hY 6080 R36-1000 R37-1000

425 R33-47

V7 83 O O e o V10 6080 V8 R38-I000 SW 83 a 425 o C,OT TG V12 V11 0., 1 10, OB-2 6SJ7 reÒ Ñ 3A C18 00 50 .--o V13 0 63 V 5A OB- 2 TO 6080,65J7

AUDIO JUNE, 1955 19

www.americanradiohistory.com while he monitors with earphones through Fig. 5 (left). With hand on record -level control, operator is positioned to set proper level for recording noises heard in playback. With phone jack. Fig. 6 (right). With both hands on editing knobs, tape is jockeyed slowly through head assembly to spot aid of earphones, exact spot is located and marked, then eliminated and spliced.

model 18WK, in Klipsch K baffle (folded wedding and other ceremonies or special meetings for later inch Electro -Voice if horn enclosure). Shelf -borne right over this, the mid -range dubbing to disc, and so on. A thing impractical to do the hollers through a Jim Lansing 500 -350 horn assembly and recorder were an integral built -in. its 375 driver, with crossover at 300 cps, the 12 db per octave network self -built. The high frequencies Marion through a Testing, Testing . . . pair of T -35 Electro -Voice tweeters, placed one on each side And again, as to safeguarding this thoroughbred equip- of the mid -range assembly, both faced towards the back of ment (music -wall or no) our reader is strong on mainte- the enclosure and triggered into chorusing by their own nance and observes religiously the prescribed rites, such as 8.000 cps crossover network. This, with the other cases and keeping tape recorder heads sterile by brushing with tetra- cabinets are ranged across the narrower wall of the approxi- chloride before and after use, and so on through the me- mately thirteen by nineteen foot room. It should give you an chanical assembly of his 350P Ampex. Neither is recording idea of the real informality of the hi -fi furniture layout, al- undertaken without checkups with an audio oscillator to though the total bill came to a rather stuffy hi for all of this assure those results we call optimum. Not excepting also, fi and one would think a music -wall might be indicated for frequent checking of the general systemic signal level : volt- safekeeping this rich hi -fi fare, if nothing else. But it ain't age analysis of amplifier with an RCA WV97A VTVM, or necessarily so. For one-and this seems to be the heart of the current measurements of tubes and resistors with a Triplett matter -as a seasoned bi -fier reader Crofford often is called 625NA unit. By measuring d.c. and a.c. voltages, the former upon to use his tape recorder on the outside. Perched atop reveals troubles in the shape of burned -out resistors, open 1 the Craftsmen TV cabinet, the portably cased tape recorder or shorted capacitors, etc.; and with the latter, he checks can be easily removed to be taken out on off- premise assign- adequacy of circuit operation to the functional requirements ments. These might be for A -B comparisons, recording of the entire system. You would tend to use such instrumentation, as our reader unfailingly does, to check out the equalization and record - head alignment so that the recording on tape will be held to unvarying maximum output of the upper frequency ranges. And you can use the audio oscillator to test the amplification wing of your own system for frequency range, output voltage and power. Indeed, this checking and re- checking of equipment for security as to optimum hi -fi results becomes important as you progress from taking your early pleasures in audio results by the "strength of your ignorance" and learn, while you listen, to listen -finally to appreciate the finer points of the technique of sound reproduction as you hi -fi with audio at home. The notion that test instruments are for trouble shooting (after the event) is OK but they are also, as used here, the electronic trouble preventive. Test instruments have a place, we venture to suggest, not only on the serviceman's bench, but just as assuredly in the dedicated audiophile's sea chest. All of this goes to show how goes the safari of a hi -fier a -hunt for linear results that will come ever closer to reconciling fact with dream. Fact, such as that amplification is developed further along of real- than speakerage ; dream, a seeking for the greatness ity in sound created as pure as can be with such, at the moment, disparate efficiencies.

Behind the Sonic Scenes Be that as it may, the fact remains that in practice and follows an exemplary pattern of audio - with shallow pullout routine our reader Fig. 9. Record playing equipment in slide drawer lab conditions by day, he listens to record- Rek turntable, Fairchild arm and cartridge; behavior. Under for stability. Shows -O -Kut or mother, or pressing discs) as a job to be done, also spirit level, stylus pressure gauge, 45 -rpm adapter disc. ings (tape, AUDIO JUNE, 1955 20

www.americanradiohistory.com Fig. 7 (left). Splicing tape with EdiTall block. Insert tape snugly in groove and pass razor blade along diagonal slot to moke true cut. Blade should be demagnetized before cutting to avoid clicks or partial erasure of tope after splicing. Small reel of splicing tape is shown. Fig. 8 (right) Operating wires and cables: Bottom row, ( I. to r.) Coaxial microphone cable with phono tips used to hook up preamplifier output to amplifier input ... Coax cable with phono plug on one end, alligator clips on other. Used for testing, phono tip into preamp out, the clips to voltmeter terminals W)II indicate signal -to -noise ratio; also checks frequency response . Coax cable, phono by on one end, phone plug on other, for connecting appropriate tope recorder output to amplifier input, to play through main speaker system . Three -wire microphone cable with Cannon XL connectors on both ends. Shown hooked up as extension to microphone cord. Middle row (I. to r.) Three -wire microphone cables, with Cannon XL connectors on both ends. Two sets shown, giving cable extra length . Electro -Voice 655 microphone with connecting 3 -wire cable -two conductors and ground - to assure low hum pickup and low extraneous noise pickup. Top row. Altec "lipstick" microphone and its own power supply with factory -equipped accessory hookup cable. Output is o balanced 3 -wire line with Cannon XL connector. Upper right: coax cable with phono tip and Cannon connector. Hooks up output of REL tuner to Ampex input for off -the -air recording to tape. intent then for flaws, in the sterile atmosphere of high -level that in the output transformer. Feedback is introduced from lighting, stainless steel and chromed apparatus. Thus it may the output transformer to the cathode of the first stage. The be that an un- bright home interior is a sort of escapist stage second stage is a split -load phase inverter, and it is coupled setting for a placid, private, unofficial kind of listening to to a push-pull driver stage; from there it goes to a push - musical offerings whose interior content is, perhaps, heard pull cathode-follower driver. thence to the output stage, whole only there, as against the fragmented note -by-note consisting of a pair of 6550's Ultra- Linear push -pull con- and instrument by instrument "snooping" in the recording nected. An OB2 is in the plate circuit of the cathode follower lab, with stop -watch holding and meter- reading intensity. drivers to keep a constant voltage at the plate of the cathode Such are the means to an end result in recording that bring follower. Fixed bias is used on the output stage and it is states of exaltation and then of deep repose to those of you adjusted by changing bias on the 6SN7GTA cathode-fol- who are aware that the science of cycling sound beyond the lower driver. (We expect you will he referring to the push -pedal or tin -ear level can be as brand -new young as schematic, Fig. 3.) All resistors in plates and cathodes, your own discovery of it through good hi -fi instrumentation feedback resistors and pli: :.' -shift resistors have 1 per cent of your own. (Continued on page 62) Such are the activities behind the sonic scenes that, in the general scheme of sound "manufacture" place ahead of the workings of the inner sanctums of designer and maker of signal- source and pickup equipment. And correspondingly, should your pre -listening ritual be full of carefully poised gestures. Just so is the disc held edge-to between palms first wiped dry. Just so is it placed on the turntable, and pickup arm (rechecked for true with spirit -level, and for pressure with gauge) wafted down upon the playing surface. To experience all the ecstasy this can bring, the lover of beauty in music must perforce become a knowledgeable knob - twirler. Adequate controls provide sensitive variation of sound to suit temperament or inclination. Thus, in this case on a Marantz preamplifier are the roll -off, the contour, the loudness, the bass, the treble controls delicately turned through an infinitesimal arc each, first one way and, closely listening, perhaps the other way. Volume is opened up then and from out of -as tt were-creation's void come the Voices.

The Amplifier Universe But not exactly a "void." Say, rather, the universe of amplification -60 watts -worth of it. The self -made amplifier and power supply in this system are mounted on two separate, self -punched out aluminum chasses, each 10 by 12 by 4 inches. The logic of their construction can be told in no better ternis than these notes on the components and their respective and related functionings. This version of Fig. 10. Rear of Ampex electronic assembly, with power supply at bop, the record and playback preamp below. Cord sets are original equipment, Ultra- Linear harbors in its circuitry two matched 5692 and connect to main amplifier. Accessories on bottom shelf include tubes as voltage amplifiers and phase inverters. The first Ampex head demagnetizer, Permo` lux earphones, tape splicing block, stage has a phase -shift network in the plate circuit to offset and marking pencils.

AUDIO JUNE, 1955 21

www.americanradiohistory.com Negative Feedback

The basic principles of negative feedback, and its use in variable damping factor and tone control circuits.

EDGAR M. VILLCHUR

LET US SUPPOSE that the power steering at which the distortion is generated, the and without measurable time delay. The system of pan automobile is (for the above explanation becomes a house of negative feedback circuit does just that; sake of argument) somewhat out of cards that can be easily demolished. It it compares the distorted output signal adjustment, in that it over -responds is only necessary to point out that the with the undistorted input, and applies when pulled to the right. The driver out -of-phase feedback signal can reduce to the amplifier a corrective signal cor- senses the trouble instaneously, and the amplitude of the faithful part of the responding to the differences between compensates for the defect by applying signal in exactly the same amount as the two. less force on right turns. This is nega- it reduces the distortion elements, thus tive feedback in operation, although it is leaving the distortion percentage un- Automatic Correction not automatic ; the feedback "circuit" changed. Clearly we must dig a little Figure 2 illustrates the automatic cor- includes the driver himself. deeper. We will see that if the negative rection applied by negative feedback. The function of an audio amplifier, as feedback signal is introduced into the The steps illustrated in sequence show of a power steering system, is to control amplifier at a point before the distortion the transmission of the signal through large amounts of power by small is generated, it acts as a pre- compen- the amplifier and back through the feed- amounts of power. The electrical signal sating element which reduces the per- back circuit; the time taken by each from a radio tuner or phonograph centage of distortion in the output step is so small that it cannot be meas- pickup cartridge, representing the broad- signal. ured by ordinary methods, and the cast or recorded sound, may have Consider the case of a pure sine wave process may be considered instanta- enough power to drive a pair of ear- applied to an imperfect amplifier. The neous. phones but is hopelessly inadequate for output signal fed to the loudspeaker will The distorted amplification of a sine a loudspeaker. Before the electrical cur- be a distorted version of the input, as wave is illustrated in (A) of Fig. 2. rents can be reconverted to sound of illustrated in Fig. 1. It is evident that Part of the distorted signal is tapped appreciable volume they must be ampli- a characteristic of this amplifier is the from the amplifier output and fed back fied,' that is, their power must be in- reproduction of positive peaks with in- to the input in such a way that the phase creased. At the same time there must sufficient relative amplitude. is exactly opposite, as illustrated in be negligible distortion -the fidelity If the entire process took place very (B). Notice that the feedback signal is of electrical representation must not be slowly we could compensate the signal fed back to a point before that at which changed. input for such a characteristic and the distortion was generated, so that The electron tubes that are the heart produce a pure sine wave in the output. the distorted signal is mixed out of 1 of the amplification process perform with As the signal approached its positive phase with an undistorted signal. good, but not perfect fidelity. Prior to peak we could turn up the level control Two things must happen. The original the universal acceptance of negative of the signal generator to just the right input signal will be reduced in strength, feedback as essential to high -fidelity position at each moment (monitoring and a corrective enlargement of the amplification, "undistorted" amplifier the amplifier output with an oscillo- first half -cycle will appear in its wave power meant maximum output at which scope) sq that the extra signal voltage form. It is as though the circuit knows the harmonic distortion was no greater would force the instantaneous amplifier what the amplifier is going to do to the than 5 per cent. One -twentieth of the output to conform to the sine -wave pat- signal's positive peak and sends in the output signal could consist of spurious tern. The erratic output characteristic signal forewarned and forearmed. harmonics not present in the original of the amplifier would then be corrected Where the defective amplifier will not input. Modern engineering techniques for at every point by an inverse charac- furnish enough gain, at the positive have been able to reduce this distortion teristic of the signal input from the gen- signal peak, the signal itself is pre - figure by a factor of 100 (leaving pick- eratotr. This would be a nonautomatic compensated by having too much voltage ups and loudspeakers far behind), and feedback system, in which the differ- relative to the negative half- cycle. The the most powerful of such techniques is ences between output and original in- output signal shown in (B) of Fig. 2 the application of negative feedback. put signals are sensed by the operator, is reduced in power but has a lower and the corrections applied manually. percentage of distortion. Feedback In Amplifiers The periods of time involved in the It is important to know that while A common explanation of how nega- amplification of an audio half -cycle, of gain is sacrificed by negative feedback, tive feedback reduces amplifier dis- course, are very small, and correction amplifier power capability is not. The tortion goes something like this: part for amplification characteristics through third step in the feedback process is of the output signal is fed back into the feedback must be applied automatically illustrated in (C) of Fig. 2. The cor amplifier out of phase, thereby partially cancelling distortion products. Such an CORRECT WAVEFORM explanation is not incorrect, but it is Fig. 1. Distorted re- DISTORTED incomplete. production of a sine - If no mention is made of the point wave signal. The ffil fIa n instantaneous am- 5 l at which the feedback signal is intro- 0 AMPLIFIER plification is reduced duced in relation to the point or points SIGNAL WITH DISTORTION SPEAKER on positive peaks. GENERATOR President, Acoustic Research, Inc., 23 Mt. Auburn St., Cambridge 38, Mass.

22 AUDIO JUNE, 1955

www.americanradiohistory.com obvious if we consider again the original quite a different pattern of variation example of the automobile power steer- from that of the output voltage) the ing mechanism. If the trouble consisted circuit is said to apply current feedback. III !!I (A) of the fact that the front wheels of the Both of these types of feedback have the car would not turn far enough, due to same effect on distortion and noise, but V a bent frame acting as a mechanical stop, opposite effects on the amplifier damp- no amount of increased force used by ing factor. OUT -OF -PHASE the driver would help. Similarly, if the Figure 3 illustrates a typical vol- FEEDBACK SIGNAL output wave form of an amplifier is tage- feedback circuit. Part of the volt- clipped because the tubes have reached age across the output transformer's saturation and cannot pass more cur- voice -coil winding is applied to the rent, or have reached current cutoff, cathode resistor of an earlier stage. no change of amplifier gain, automatic has ORIGINAL This the same effect as applying the SIGNAL or otherwise, can change the instanta- signal directly to the grid, but provides neous value of the current being passed. the additional convenience of a low - (B) Feedback can only help in those situa- impedance path. tions where an instantaneous FEEDBACK variation Figure 4 illustrates a current feedback SIGNAL in gain will produce a change in output. circuit. As the speaker's impedance Another limitation of negative feed- changes at different frequencies, due to back is inherent 1flluanl in the amplifier com- changing back -emf's the signal current (C) ponents themselves. The feedback cir- through the secondary circuit and cuit is designed to apply its corrective through R changes correspondingly, signal 180 deg. out-of- phase, but this although the signal voltage applied to phase relationship just does not hold up the speaker may be unaffected. The feed- at the extreme low and high frequencies, back signal is taken from the IR'voltage Fig. 2. How negative feedback corrects for especially when the output transformer drop across R rather than from the distortion. The steps illustro'ed take place is within the feedback "loop." The phase is practically actual signal voltage, and thus con- instantaneously. shift that occurs at the frequency ex- trolled by the output signal current. tremes can be so great that the feed- rected input signal is increased to bring back becomes positive, in which case Variable Damping Factor it back to its value before the application of feedback, and the original output A combination of voltage -controlled power is restored at lower distortion. and current- controlled feedback can be Not only is the power-output capability used to provide an amplifier with a of an amplifier not reduced by feedback; variable damping factor. The two cir- the power output at the original maxi- cuits can be so ganged that the net mum distortion rating is actually in- negative feedback, and hence the net creased somewhat. It is necessary, how- effect on distortion and noise, remains ever, to drive the amplifier harder, that the same. is, to provide a higher input signal. The amplifier damping factor may be defined as the ratio between the speaker Amount of Feedback impedance and the source impedance which the speaker "sees" looking back Not too long ago audio amplifier into the amplifier. A high damping fac- specifications might have listed "nega- tor means that the speaker sees a very tive feedback circuit" as one of the low resistance, and that this low resist- desirable features. Today the existence ance acts as an electrical brake on the of such a circuit is assumed, and the speaker. Any voice -coil vibrations un- specifications often describe how much Fig. 3. Typical negative voltage feedback authorized by the amplifier signal (such feedback is used. The amount of feed- circuit. as hangover vibrations, which tend to back, in decibels, is the ratio of the occur after a heavy stimulus in the original signal voltage to the corrected amplifier gain and distortion are in- region of speaker mechanical reso- signal voltage; thus the number of db creased or the circuit begins to oscillate. nance) must send current through the of feedback also refers to the reduction Too much feedback used over a cir- source resistance -the speaker is not of amplifier gain. cuit whose phase shift is too high re- only a motor but a generator -and with For example, suppose that a 30-watt sults in low- frequency "motor- boating" a low value of source resistance the amplifier is driven to full output by an (the name given to oscillations of sub- speaker is immediately braked to a halt. input signal of .025 volt prior to the sonic frequency because of their char- (Continued on page 70) application of negative feedback. Twenty acteristic sound) or high- frequency db of feedback (a healthy amount for an squeals. Some of the worst effects occur audio amplifier) means that the amplifier when the oscillations break out only gain has been reduced to one -tenth, and on signal peaks, producing distortion. 025 volt input will now be required to The effect of high -frequency oscillation produce the same 30 watts. If the feed- often imitates speaker rattle to per- back is applied in such a way as to be fection. fully effective the distortion and noise The successful use of large amounts will also he reduced by a factor of 10. of feedback is thus only possible with amplifiers which are of high quality to Limitations of Feedback begin with. However, the application of Negative feedback seems to work moderate amounts of feedback can pro- wonders, but it is not magical, and it duce dramatic changes in low -cost does not work against all types of dis- circuits. tortion. It is completely wrong to design an audio amplifier carelessly and to Types of Feedback assume that feedback will take care of When the corrective feedback signal any trouble. An amplifier circuit should is controlled by the output voltage the be as "clean" as possible before feed- is circuit said to apply voltage feedback; Fig. 4. Typical negative current feedback back is introduced. when the feedback signal is controlled circuit. The feedback voltage is dependent One limitation of feedback will appear by the output current (which can have upon the current flow in the speaker circuit.

AUDIO JUNE, 1955 23

www.americanradiohistory.com A Novel Tape Recording Amplifier'

A. F. FISCHMANN

The author describes a recording amplifier which provides a constant -current source for the head. This characteristic is achieved by applying current feedback from the load of the amplifier to its input.

THE PURPOSE OF A RECORDING HEAD IS utilizing the total output available. The to provide uniform magnetization for necessary high output resistance of the the tape over the frequency range amplifier is achieved by applying cur- covered by the amplifier feeding it. As rent feedback throughout the amplifier. the magnetizing force is proportional to This results in an output resistance the curent flowing through the head, which is practically equal to the value such a characteristic is achieved by con- of the load resistor RL. of the output necting the recording head to an ampli- tube in Fig. 3. The advantages resulting fier whose output current is proportional from such an arrangement are three : to its input voltage. Such an ampli- (1) The amplification is linear and fier is characterized by an extremely independent of the tube character- high output impedance compared to the istics, owing to the strong feedback. impedance of the load, which is in our (2) The frequency response may case the recording head in series with be influenced by including a fre- Fig. 4. A simplified form of the author's ampli- the coupling capacitor C in Fig. 1. As quency- selective network in the feed- fier has a choke for high- frequency com- the recording head is, for all practical back path. This network can consist pensation. purposes, a pure inductance, the con- of extremely low impedances and is stant current flowing through the re- GL, = GL, =0, the value of the output therefore not subject to capacitive conductance cording head creates across its terminals pickup. It may be connected through increasing by 6 db per 1 a voltage drop Y r=gr,.(1_ (2) octave and reaching a considerable am- 1 + ßGk ) plitude at high audio frequencies. where The problem of recording amplifiers 1 is solved conventionally by connecting +(gm, +gin) gm, gp, the recording head to a voltage amplifier gnu+gv, through a high resistance as in Fig. 2. (gpl ) However, this has the disadvantage that But fIGkcl; therefore I - ßGk. over the greater part of the frequency 1 + ßG range only a small fraction of the avail- is in the re- and . For practi- able output amplitude used Yoor gp. ßGx cording head, the rest being uselessly 14.4.10' dissipated in the series resistor R. In cal values of g. and gp, Zout= the recording amplifier described in this ,gr. GI article and shown in basic form in kilohnts. Your may therefore be neglected to Fig. 3, the load is directly connected Fig. 3. Basic theoretical diagram of the au- in comparison with GL. = --, the latter the anode of the output tube, thereby thor's constant- current amplifier. Note current feedback loop around entire amplifier. solely determining the output impedance * 390 Park Place, Brooklyn 38, N. Y. of the amplifier for all practical pur- 'Work done while with Israeli Ministry poses. The idea suggests itself to insert long leads to a conveniently located of Defense, Scientific Department. a suitable choke in series with RL, in switch correcting the frequency reorder to make the output impedance of sponse for different kinds of tape or the amplifier rise in the high audio - for different speeds. range at a rate similar to the delivered by the frequency (3) The power rate of increase in the impedance of the output tube is fully utilized. A 6SL7 head. This was, however, not RN recording is amply sufficient to drive a conven- found to be necessary in the author's tional high -impedance head. design. A simplified version of this amplifier consisting of one tube is shown in Fig. 4, Bias Injection and might be suitable for certain appli- Supersonic bias of considerable am- Fig. 1. The ideal recording amplifier give cations. The output conductance of this plitude must be impressed on the tape constant -current output. circuit simultaneously with the audio frequency. This bias is usually fed into the record- Yone= rp ing head in parallel with the audio fre- +Rn(µ +1) +RL. (1) same method were ap- c R quencies. If the Rk may be designed so as to make rÿ plied to the amplifier described in this sufficiently high to drive a recording article, the full bias amplitude would head over a reasonable range of fre- appear at the anode of the output tube quencies. However, the tube would then and would he fed into the amplifier need a driving voltage of about 20 volts through the voltage divider consisting which will hardly be provided by a pre- of rp, and Rk. Therefore, a double triode is The input signal etc (Fig. 3) is as- Fig. 2. Usual method of operation is to use a amplifier. added, and the feedback is extended over sumed to be zero, and a voltage e is medium- impedance amplifier with a large and series resistor to achieve constant recording - two additional stages as shown in Fig. 3. applied between the output terminal head current. This is wasteful. For further simplification, assuming (Continued on page 74)

24 AUDIO JUNE, 1955

www.americanradiohistory.com PHONOGRAPH EQUIPMENT

A SECTION Or

AUDIO JUNE. 1955

"Look, aren't you carrying this compliance business a little bit too far?"

Without the phonograph, our listening would be restricted to whatever music happened to be available on the radio, and would _re only that which someone else chose for us. To get the excellent reproduction possible from modern LP records demands a careful attention to the selection of equipment and a thorough understanding of its characteristics and their relation to quality.

www.americanradiohistory.com THESE PAGES PROVE HOW THE GARRARD RC8O

Original RC80's already had these important features

Pusher -type Platform: Adjusts simply to 7 ", 10 ", l2" records, regardless of diameter or size of spindle hole. The only device that assures positive gentle handling of all records. No overhead bridge to damage or dislodge records accidentally.

Automatic Stop: Insures positive and unfailing action at end of any type or size of record. When you buy the Garrard R.:80. r3u benefit f-om_ Pull -away Idler Wheel: Avoids flattening of drive millions cf playing hears wheel when changer is not operating. it t,a home, teeing ever? basic feature.

Heavy Drive Shaft: A unique feature, providing more consistent quality at critical low (331/3 and 45 rpm) speeds. Wows and wavers eliminated. $49 50 net: {ers cartridge

Convenient Start -Stop -Reject Lever; and Triple -Speed Switch: Controls are combined and located away from tone arm ... an important precaution for safety of stylii.

Heavily Weighted, Balanced Turn- table: Imparts flywheel action, so that any variations in drive motor are not reflected in record reproduction. No turntable rumble.

Balance- Mounted Tone Arm: Exclusive "parallel - lift" construction guarantees true -tangent tracking. Disturbing resonances eliminated.

Interchangeable Plug-in Heads: Engineered to accommodate user's personal choice of virtually any high fidelity cartridge ... crystal, ceramic or magnetic.

Advanced Heavy-duty Silent 4 -Pole Motor with Absolutely no Rumble: Assures no -hum when used with sensitive magnetic pickups! Speed Two InterchanzaaslE Soinmes: Easily nserted maintained regardless of wide variation in line raryova)la so that recnds seed and inst3ntlr le -arm is in voltage. No appreciable speed effect operating upwards ever metallic spindle prc- Mngrsg Switch: No sonic 1Jr tone not to ripped undistu,bed, unit "cold" with full load or "hot" with single jectisns afte' pla.inr. as ar ordinary changers. chi sging cycle. Continn t >r music b1 -extesnaors noises. record, regardless of weight, thickness or dia- The -.wo Gavel ;p-r -las :ccommoda-e all rec- meter of records. ords as tha wee misruled to be played (a)Gerraed "bait" spilc le or standout center cl replacemeit holes. Heavily pia -3d. perfectly smooth, as a A complote stock be mov ng parts to lick and Watch -like Construction: All levers fully adjust- spindle thou .d be axai able to all of precious records. parts is readily able easy, inexpensive to service. Bronze enla-ge . entar io es ... (b) Easi y insaßed ride spindle, av3lablk as bearings at all moving points for longer life! Garrard owners Precision ground gears perfectly meshed to in- an accessory for -15 spry records. sure constant, smooth action through years of service.

www.americanradiohistory.com World's finest Record Changer

through advanced engineering, rigid quality control

By now -all RC80's have these additional features

New! Stylus- pressure adjustment. Accessible from top. Prolongs life of records by enabling user to keep weight of stylus, on delicate record grooves.correct for any type of pickup cartridge, easily and at all times.

New! Foolproof Record Pawl Golde: Lengthened to handle records even thinner or thicker than standard, for any record material, any speed.

New! Exclusive Garrard Crowned Inte' wheel: A Check craftsmonsh'p, costly feature preventing even the slightest flutter or rumble. performance, price and service and you New! Manual play ... of selected record bands while tracking: RC80 tone arm sets down and will understand why lifts up perfectly and automatically for years this is truly the without slightest danger to record grooves. This is recommended as the safest manner to play world's number one records. However, professional -type finger lift permits manual handling of pickup arm, except high Fidelity only when unit is in midst of changing cycle. The arm is completely free to be moved by user record changer' to any part of record while tracking.

There's no need to pay more for a record player regardless New! Rumble -free Spindle thrust of other assembly ... Supported by components in you: high fidelity system Garrard -designed washer of special plastic ...more durable than metal, as on ordinary changers.

New! Main Turntable Spindle ... prevents wow. Bearings are sintered bronze, expertly burnished to size .., and revolve freely and smoothly in exclusive Garrard bakelite cage, eliminating noisy metal -to -metal contact and the binding "creepage" found in steel cup races used by many record changers.

New! Exclusive Drive Belts ... Insulate against any possibility of rumble and operate without slippage for years. However, replacements cost pennies ... are always available for changeover within minutes by owner. No long interruptions in use of changer ... waiting for replacement gears or bearings.

New! Special soft, flexible motor leads ... Avoid any possibility of even slight vibrations being transferred to base plate.

New! Exclusive one-piece moulded condenser - resistor network... eliminates startling "plop" noise when changer shuts off at end of last record.

For 16 page booklet. "Sound Craftsmanship" New! Exclusive! Motor armature dynamically bal- New! Completely wired.. ready for plug -in! names of dealers, mail this coupon. anced...super -finished and Individually weighted RC80 comes with UL- approved line cord and to very fine limits, by special Garrard process. moulded plug; and with pickup t cable, terminat- Insures quiet, perfect speed through years of ing in standard jack. let British Industries Corporation, Dept. A6 -5 operation. i 164 Duane Street, New York 13. N. Y. New! Mounting grommets of exclusive material, Gentlemen: designed to keep out vibration. Please send "Sound Craftsmanship' and A quality endorsed product Garrard dealers' names. New! Exclusive "snap- mount" spring assembly a' the British Industries Group Permits instantaneous mounting of changer 1 Name

and adjustments to level from top of unit, with 1 Garrard. Wharfedale, I simple screw dr ver Leak. I Address 111, Genale:, Multitore and I I City Zone Stag t ether high fidelity components. v : I

www.americanradiohistory.com Phonograph Equipment

C. G. McPROUD

A practical discussion of the characteristics of phonograph pickups, turntables, and record changers and the role they play in providing high -quality sound reproduction from the widest possible source of music in the home -records.

and of 20 db on commercial WHEREVER k: FIND a home music Not only does the stylus have to carry (vertical) system nowadays, we are likely the arm over the record and thus over- phonograph records. Today we get to find the facilities for record come the friction of the arm bearing, it around 40 easily. reproduction, for even with access to often has to actuate stops for automatic The 9A was, however, one of the first radio reception in areas where there changers. Remember that the LP pickup practical moving coil pickups, and used are "good music" stations, one can never rests on a stylus which has a radius of a principle which-at least theoretically be sure that he will be able to hear the only 1 /1000 of an inch, and that this -has some important advantages. In music he wants when he wants it. stylus is driven by a groove of smooth this type of pickup, the stylus actuates a in To be sure, there is much good music material that has sides 45 deg. from the tiny coil of wire which is located a out of moving -coil model played throughout the country over the vertical so the stylus can climb magnetic field. One air, and depending upon where the lis- the groove without too much effort. It was placed on the market in 1938 which is located, considerable entertain- is easy to see that the bearings of the consisted of a structure resembling the tener speaker. ment is available without cost -if we arm-both vertical and horizontal -must voice coil and cone of a dynamic may discount the time and nervous en- be almost as delicate as those for the bal- The outer edge of the cone carried the ergy expended in listening to commer- ance staff of a watch. Let us now con- voice coil, and the stylus was cemented cials. But even that is little enough to sider the individual units that make up to the apex. This coil was suspended in trade for the many hours of musical a modern phonograph -up to the point an air gap on a thin ribbon which was entertainment that are free for the ask- where the amplifier enters into the under a 15 -pound tension, and was ing. The one drawback to radio music picture. "tuned" to control the resonance. How- is that the only offerings available may ever, this pickup-the Miller-was quite happen to be chamber music when we Phonograph Pickups delicate, and the tiny cone was easily want a symphony orchestra, or an hour The phonograph pickup is a electro- damaged. Today's moving coil pickups in of modern music may be all that can be mechanical transducer which converts employ coils little larger cross section found when we want a sleep- inducing motion into an electrical signal. The than a shingle nail. Some have the coil concert of organ music. Therefore, we motion is imparted by a groove in a arranged so as to rotate in the magnetic turn to the phonograph for music of phonograph record which undulates field like a d'Arsonval meter movement ; our choice, and not only do we have an rapidly from side to side, often as rapidly in others the coil is simply moved within enormous repertoire to choose from, but as 15,000 to 20,000 times per second. the field. One of the advantages claimed we are offered the same music played During this undulation, the stylus at- for the moving coil type is that the coil by a variety of performers. And, with tains a velocity of more than 25 centi- moves in a uniform magnetic field, even reasonable care in the treatment of the meters per second on some records, although it may not be perfectly centered. records, the cost is likely to be only a though this is far too high for best Therefore, the displacement of the sty- few cents for each playing -far less than quality. lus from the exact center of the magnetic the price of a concert ticket. The conversion of energy from me- field does not introduce any distortion. considerable variety of equipment chanical motion to electric current is Furthermore, the coil mass can be re- A duced to a minute value, thus raising is required to play phonograph records. accomplished in a number of ways, and We must first have a means for turning as far as the transducer action is con- the resonant frequency between the coil the record round and round at a constant cerned, one of them is as good as another. and its suspension. In many models, this and accurately maintained speed. This However, some require more mechanical resonant frequency is well above audi- seems a fairly simple requirement, but force to move them, and resonances be- bility. the better our reproducing equipment tween the mass of the moving parts and The most commonly encountered mag- becomes, the more critical are the de- the compliance of the restoring force netic pickup is the moving iron type, in mands made upon the rotating machin- introduce deleterious effects. which a small vane or tube swings be- ery. With the usual "package goods" The first pickup to follow the old tween the poles of a magnet, and type of phonograph, response at both low acoustic "sound box" was the magnetic. changes the reluctance of the magnetic and high ends of the frequency spectrum In early models, these consisted of an path, thus changing the lines of force is usually comparatively poor, and the armature which was vibrated by the cutting through a coil. The mass of the effects of rumble and flutter are less needle between the poles of a magnet. moving iron has been reduced greatly noticeable. A coil of wire surrounded the armature, from early models, and performance is Another device we must have to play and as the iron armature or vane moved. uniformly good in most high -quality phonograph records is the pickup -the it changed the number of magnetic lines magnetic or variable reluctance pickups. device that carries the "needle." Within of force cutting the coil, and in turn, The crystal pickup first became popu- the last ten years, the development of generated a current. Early magnetic lar in the early 30's. Even the first of pickups advanced greatly, and some of pickups were heavy, some requiring as these types were lighter than the mag- the units used today in high -quality much as 6 ounces of stylus force to actu- netics then available ; not only that, but home systems are far superior to the ate them, although most of those in use they were much less expensive in them- best used commercially before LP's. in the early 30's worked with around selves, and they required less amplifi- Then we must have some means to 2 ounces. The Western Electric 9A re- cation because the output signal was carry the pickup over the surface of the producer was a great improvement. and much greater. Thus the manufacturer record, remembering that the pressure it worked with a stylus force of only 35 saved in cost of pickup and saved in at the stylus is likely to be around 6 grams -1% oz. Catalog sheets for the having to put less tubes in his instru- grams on an average -rarely more than 9A specify that it would give a signal to ment. Early models used relatively large of 10, and occasionally as low as 1 gram. noise ratio of 45 db on transcriptions crystals, and the resonances the crys- AUDIO JUNE, 28 1955

www.americanradiohistory.com tal itself introduced peaks and valleys upward to about 8 x10-6 for most models, better. It influences the resonant fre- in the reproduction to give what is with the Weathers pickup being rated by quency since it is this mass which res- still remembered as a typical "crystal the manufacturer at 14 x 10-6. In gen- onates with the compliance of the sus- sound." Modern crystals are consid- eral, the higher the compliance the less pension. The lower the mass, the higher erably smaller, and the resonances have the record wear, although other factors the resonant frequency is likely to be, been eliminated or reduced so as to be may enter into the performance. and in the better pickups it is above the unobjectionable. The term compliance is generally used audible range. The operation of the crystal pickup to signify lateral compliance, although Weight. The weight of a pickup is depends on the piezoelectric principle. vertical compliance is also of interest. not important -in most instances -since When certain materials -among them Since the groove is cut by a chisel - it is possible to counterweight the arm Rochelle salt, which was the usual crys- pointed cutter, it is narrower during to compensate for the additional weight tal employed for pickups-are deformed lateral excursions than it is when it is of the pickup itself. However, with a mechanically, they develop a voltage on unmodulated. Thus the stylus is forced heavy pickup it is possible that the in- their opposite faces, and foil electrodes to ride up and down, since it rides higher ertia of the pickup in the vertical plane cemented on these faces serve as the in the groove when it is narrow than may be so high that the pickup cannot terminals of the generator. All piezo- when it is wide. This is called the follow warped records easily. Therefore, electric substances are amplitude sensi- "pinch" effect. Vertical compliance is if the pickup is heavy, it should have a tive, which means that they generate a necessary to permit the stylus to follow highly compliant stylus suspension in voltage which is in proportion to the the pinch effect without undue wear on the vertical direction. amplitude of the amount of deflection the record. One other important con- Stylus Force. This term is often con- applied to them. Since modern phono- sideration is that the vertical motion im- fused with both pressure and weight. graph records are cut with a character- parted to the stylus by the pinch effect It is the force with which the stylus istic which is a close approximation to or by warped records should not be bears upon the record, and can be meas- a constant -amplitude curve, the signal translated into an electrical signal. No ured with a scale or balance just as generated by this type of pickup is prac- modern high -quality pickups have much though it were weight. The correct term tically "flat" and only a small amount of trouble with vertical translation, how- is stylus force and it is measured in equalization is required for complete ever. The check for it would be to play grams. Modern pickups seldom require correction of the characteristic. a vertical cut record -the old "hill and more than 6 to 8 grams for perfect trac- The first ceramic phonograph car- dale" records formerly used for tran- ing in the groove, with many work- tridge was made by Sonotone in 1946, scriptions -and listen for any output. ing perfectly in the range from 2 to and today most of the piezoelectric car- Styli are often mounted on a "shoe" 4 grams, and the Weathers with 1 -gram tridges use a ceramic element rather which is compliant in a vertical direction stylus force. Some authorities are of the than the Rochelle salt. The ceramic ele- but which transmits all of the lateral opinion that the proper value is 6 grams ment itself is not unlike a small piece motion to the moving element. for any pickup, and that any less stylus of fine china. During the manufacture, it Compliance may also be thought of as force will cause more record wear than is exposed to a strong electrostatic field the opposite of stiffness. Thus a com- the 6 -gram value will. This is debatable, so as to polarize the molecules in the pliant pickup is one in which the stylus however, although it seems probable material. When it is completed, it is is free to move from side to side easily that a given pickup would cause less responsive to mechanical stress -i.e., it and without stiffness. record wear with a certain minimum is piezoelectric -and will generate a Effective Mass. This is the name given of stylus force and greater wear if the voltage when it is bent or twisted. Ac- to a lumped mass at the stylus tip that force were reduced because of a faulty cording to Sonotone, modern ceramic would result in the same mechanical contact between the pickup stylus and cartridges have compliance several times impedance as that caused by the moving the groove, on the same principle that a that of old crystal cartridges, and in ad- parts of the pickup. It is a value which light automobile will wear tires out dition have the advantage of not being permits calculation of some of the other faster than a heavy one, all other things affected by heat or humidity as Rochelle characteristics, but to be readily use- being equal. The correct value of stylus salt is. At a temperature of around 130° able in such calculations, it must be force depends on both the pickup and the F., Rochelle salt is likely to melt, turn- lumped at the stylus. In practice, it arm on which it is mounted. ing to liquid and becoming completely ranges from 1 milligram to about 5 The way to determine what minimum useless as a phonograph pickup. Some- milligrams, and the lower the value the stylus force is required is to play a con- times permanent damage can result from exposure to high temperatures even though not sufficient to melt the crystal. They must also be protected against high humidity. Neither of these conditions affect the ceramic element, which makes this material ideal for the piezoelectric pickup.

Pickup Characteristics In the discussion of pickups, one en- counters the terms used to identify the various characteristics. These are: compliance, effective mass, weight, stylus force, impedance, load resistance, frequency range, and output signal. Some of these terms are self explanatory, but others may be unfamiliar. Compliance. The ratio of displacement of the stylus to the force applied, expressed in centimeters per dyne (cm/ dyne). This is a very small numerical value, and is expressed as X x 10-6 cm/ dyne, with X representing the numerical unit of interest, and the one used to compare this characteristic of different pickups. The range in which high - quality pickups will fall is from 1.0 x 10-6 "I can't find the stylus, Lut the cannier worn."

AUDIO JUNE, 1955 29

www.americanradiohistory.com stant- frequency test record and observe for best performance of his pickups. Frequency Range. The frequency the output on a 'scope although the dif- When the impedance of the pickup is range of a pickup is usually specified by ference can be heard by an acute ear. almost entirely resistive -as with most the manufacturer in figures substantially As the record plays, reduce the stylus moving-coil models -practically any like 20 to 20,000 cps ± 2 db, for example, force gradually until distortion shows on value of load resistance can be used. In some instances this will be measured the 'scope screen. Then increase the However, when the impedance has an directly from a phonograph record which force until the distortion disappears. appreciable reactive component, its in- has been calibrated, and in others it The test should be made at a stylus ductance will resonate with the input will be the result of measurements made velocity of at least 15 cm/sec. to ensure capacitance of the amplifier-which in- with some form of device which is de- satisfactory operation on high -level pas- cludes the capacitance of the connecting signed to impart motion to a phonograph sages. leads-as well as with its own distributed stylus to simulate the playing of a Impedance. The impedance of a pickup capacitance, and introduce a resonant record. In either case, it should include is usually expressed in ohms, and will peak followed by a sharp cutoff. The cor- the effect of the record medium, as will range from a fraction of an ohm for rect value of load resistance will nullify be observed in the specifications of some a ribbon pickup to several hundred thou- the peak, and provide smooth response manufacturers. sand ohms for a crystal or ceramic car- up to the cutoff point, beyond which the The frequency range of most modern tridge. Most moving -coil pickups range response will fall off at the rate of 12 pickups is adequate for the available around 1 to 10 ohms-the Fairchild 220 db per octave. commercial phonograph records. While being an exception with 170 -while the Lower than normal values of load some might not be sufficiently good for variable reluctance types are likely to resistance will cause a rolloff of the dubbing in professional applications, it fall between 1500 and 5000 ohms. The high frequencies -in fact, some ampli- must be remembered that the average impedance of a magnetic pickup -either fiers make use of this as a rolloff control. high -fidelity pickup of today is far moving coil or variable reluctance-is Since the values will differ with every superior to the best professional models made up of the d.c. resistance of the make pickup, this is not particularly in use ten years ago. winding added vectorially to the induc- practicable, for the user must change the Output Signal. The output signal from tive reactance. High values of imped- values when he changes pickups. a pickup is usually expressed in volts - ance require the use of low- capacitance Most moving-coil pickups are designed or millivolts-and ranges from about leads to the amplifier to avoid loss of to work into a step-up transformer to 10 to 70 millivolts for the average vari- high frequencies and the introduction of increase the signal voltage sufficiently able reluctance model. Some high -out- a peak somewhere in the high -frequency to over -ride the input-stage noise and put types may go as high as 100 mv. region just before the cutoff begins. hum. The secondary of the transformer but these are rare in high -fidelity ap- The impedance of a crystal or ceramic may or may not require a resistor, de- plications. With the matching transfor- cartridge is high because these types pending upon the pickup and the trans- mer used with the moving -coil models, are equivalent to a constant- voltage gen- former design. the output signal is likely to be from erator in series with a small capacitor - Since the crystal and ceramic types 30 to 60 mv, but the output from the its capacitance being that of the car- are equivalent to a generator in series pickup alone is of the order of 1 to 3 tridge itself. This is usually in the range with a small capacitor, the load resis- mv. The Fairchild 220 has an output of from 500 to 2000 µµf. The numerical tance should be high to avoid attenu- 5 mv, which is in line with its higher value of impedance is the capacitive ation of low- frequency response. The impedance of 170 ohms, and a transfor- reactance of the pickup at a specified correct value is usually specified, and mer is not usually required with modern frequency- usually 1000 cps. ranges from 2 to 5 megohms for optimum amplifiers. Load Resistance. The load resistance response. When the load resistance is is usually specified by the manufacturer lowered, the low-frequency response is Pickup Arms reduced, and by proper choice of resis- Pickups must be supported over the tance for the load, the pickup may be record surface and caused to move from We sell every record. made to become velocity- responsive be- outside to inside in a definite predeter- 'changer, but have found low a given turnover point -so that it mined line. Any longitudinal vibration the GARRARD RC80 be can simulate a magnetic pickup. Then of the stylus with respect to the arm to the bass -boost preamplifier must be em- pivot will be translated by the pickup a consistently excellent ployed to provide proper response. Elec- into a frequency modulation of the performer. Our customers tro -Voice makes use of this character- music which is intolerable in high - say plays records istic in the new 80 series which is pro- quality systems. it all duced in several types as exact replace- The design of the arm has a large without damage, rumble, ments for some of the popular magnetic bearing on the performance of the or wow. Since this is the pickups. pickup, since at the frequency at which main function of a fine By proper choice of shunting capac- the stylus compliance resonates with itor and resistor across the output of a the mass of the arm a peak will be in- record changer, we always magnetic pickup, the low -pass feature troduced to the response curve, usually recommend it. The may be put to good use. To make such somewhere below 100 cps. In addition. GARRARD RC80, a low -pass filter, determine what value any torsional motion of the arm itself of capacitance will resonate with the in- is likely to introduce another resonance "World's Finest Record ductance of the pickup at approximately somewhere between 100 and 300 cps. Changer". Ask for a dem- 0.8 times the desired cutoff frequency In good arm design, the low- frequency onstration at (the point at which response is down 3 resonance should be below 20 cps. In- db) and connect it in shunt across the creasing the mass of the arm will lower pickup. This will cause a peak just be- the resonant frequency, but may also in- fore cutoff, and by connecting a resistor troduce another problem in the form of ESnAlLISN,D 1017 having a value of 1.2 times the cutoff decreased vertical compliance due to the HARVEY frequency across the pickup and capac- inertia of the arm. The Fairchild and RADIO COMPANY, INC. itor, the response curve should be Pickering arms both employ a relatively smooth up to the cutoff frequency and large mass for the arm itself, but sup- "Our Auditorium is the then should roll off gradually to a maxi- port the pickup vertically by means of a mecca for music lovers and mum rate of 12 db per octave. This is a spring -loaded mechanism. This increases E' audiophile from all parts simple approximation, but should fall vertical compliance without sacrificing of the world." within 10 per cent of the desired fre- lateral inertia, and is considered by some 103 West 43rd Street, quency. The capacitor value and the to be the ideal arrangement. New York City. shunt resistor value should best be de- If there is sufficient vertical compli- LU 2 -1500. termined by measurement. ance in the stylus mounting, the effect of

30 AUDIO JUNE, 1955

www.americanradiohistory.com P I C K E R I N G models 2'2O/caririciges 24o 9a/edegklezo 911e We i teed .. they are sold separately for all standard arms or mounted back -to -back to make up the famous PICKERING 260 TURNOVER PICKUP.

The 220 and 240 are engineered to maximize performance. By comparison they MODEL 220 -for 78 rpm records are without equal diamond or sapphire stylus ...

The 220 ,ltl,l 240 ate 51/2 MODEL 240 -for 33 Vs Lighter- grams and 45 rpm records diamond stylus only Smaller -5/8 by 34 by 3/e Inches

The 220 tltl 240 have MODEL 260 -turnover cartridge for 78 or 33' Highest Output -30 millivolts /1Ocm /sec. and 45 rpm records (the 220 and 240 More Compliance with Less Tracking Force back- to back) Lower Overall Distortion Less Moving Mass Wider Frequency Response Mu -Metal Shielding for Less Hum

These characteristics have real meaning to those who understand that maximum performance depends upon components which meet professional standards. If you want the best that high fidelity can offer, ask your dealer to demonstrate the 220, 240 and 260 Pickering cartridges . . . _9 6ft../i 4 ?c9 d wo 94j (12err-Oveliceeti

PICKERING and eompang inv.orpora/trd Oceanside, L.l., Newlin* ANL _AM

PICKERING COMPONENTS ARE PROFESSIONAL QUALITY . ófoiewi,dcaw 'le (I/ Ce

. Demonstrated and sold by Leading Radio Parrs Distributors everywhere For the one nearest you and for detailed literature; write Dept. A -7.

AUDIO JUNE, 1955 31

www.americanradiohistory.com EVERY PERSON WHO OWNS OR PLANS TO OWN

A FINE HOME MUSIC SYSTEM MUST FACE THIS QUESTION:

"Shall I buy a Turntable

or a Record Changer ?"

The following statement represents the point of view of there is an element of wear introduced whereby the spindle hole of the one of America's leading manufacturers of professional record may become enlarged, and cause off -center wow. Similar wear recording and playback equipment. can result as the record is dropped, and it slides down the long spindle. The choice between record changer 12-inch long -playing record disc pro- and turntable is, for the most part, vides about 25 minutes of music. The A third advantage peculiar to Rek -O- entirely personal to the user. It de- same 40 minute composition now re- Kut is that the turntable itself is ma- pends upon what he wants. If it is quires only two sides of a 331/2 rpm chined from aluminum castings. Alu- merely the physical comfort of hear- 12 -inch record. The long -playing rec- minum is unaffected by magnetism, ing hours and hours of just music, ord has also brought tremendous im- and therefore, the turntable exerts no without manual intervention, then provements in the quality of recorded 'pull' when used with a magnetic cart- the choice would be a record changer. sound. As a result, the older 78s are ridge. With steel and other magnetic On the other hand, if it is his desire to rapidly becoming obsolete among seri- materials, the magnetic pull may ac- enjoy the utmost in sound quality, ous music lovers. tually cause the stylus to 'ride the then a quality turntable is certainly groove' with a pressure considerably indicated. In broadcast studios, for The High Quality Turntable greater than recommended. example, where reproduction quality The turntable is basically a simple is of prime importance, turntables are device. A manufacturer who desires Conclusion used exclusively. to create a high quality instrument High fidelity is rapidly becoming a can devote all of his engineering skill part of our home life. This is expres- The Record Changer to the one important function of the sive of the typically American desire The record changer is an extremely turntable: its rotating motion. A for the enjoyment of finer things. As clever device, and much ingenuity has Rek -O -Kut turntable, for example, specialists in the field of professional gone into its complex mechanism. It offers the closest approach to perfect sound reproduction,and having served originated in the days when 78 rpm motion ; with virtually no rumble, this field for years, we welcome the was the only popular record speed, wow, flutter, or other mechanical dis- fact that this wonderful experience is and the playing time of a 12 -inch rec- tortion. now being adopted in the American ord was only about 4 minutes per side. There are other important advan- home. A complete 40 minute musical compo- tages to the turntable. Once the angle Rek -O -Kut precision turntables are sition required at least 10 sides or 5 between the stylus and record is estab- among the finest in the world. Every records. The record changer made it lished, it remains constant for all time. detail of their construction is care - possible for these records to be played In the case of the record changer, this fully engineered to provide the finest automatically, without the need for angle varies, depending upon the num- quality record reproduction. Whether getting up every three or four minutes ber of records stacked underneath the you now own or plan to own a music to change records. record 'in play'. system, we urge you seriously to con - A turntable has a 'live' spindle, mean- alder one of the several Rek -O -Kut The Long 'Playing Record ing that it rotates with the table turntables. You will find that it makes The long -playing, microgroove record and the record. The spindle of most all the difference in the world. has changed all of this. Each side of a changers remain stationary so that Literature on Request

Export Division. MORHAN EXPORTING CORP. THE REK -O -KUT COMPANY 458 Broadway, Nw York 13, N. Y. Cob's: MORHANEX Makers of Fine Recording and Playback Equipment In Conodal ATLAS RADIO CORP., Ltd. Engineered for the Studio Designed for the Home 560 King Strut, W., Toronto 28. Dept. LF -1, 38 -01 Q Boulevard, Long Island City 1, Now York

32 AUDIO JUNE, 1955

www.americanradiohistory.com increased inertia of the arm in the verti- which employs a novel arrangement of The high- quality turntable is designed cal plane should have no deleterious two arms so disposed that the axis of for years of reliable service with a min- effects, so the choice of arm should be the pickup is carried tangent to the rec- imum of rumble, flutter, or wow. It is governed somewhat by the pickup to be ord groove all the way from the outside often provided with integral means for employed in it. Thus it may be consid- of a twelve -inch record to a groove only levelling, has space for a preamplifier ered desirable to use the arm offered four inches in diameter with an error and perhaps for a controllable compen- by the pickup manufacturer. of less than one degree throughout. Four sator, and it does provide a constancy In making the masters from which bearing points are required, and in this of speed that is not likely to be found phonograph records are made, the cut- arm they take the form of eight needle - in any other type of equipment. ting head is almost universally carried pointed pivots riding in steel inserts. The high -quality single -play turn- on a mechanism which moves the stylus Friction is low, and there is no excessive tables offered to the high -fidelity trade along a radius. In reproduction, the play in the pivots. are simply scaled -down professional stylus is carried on an arm which is Most pickup manufacturers offer their turntables. Most home users have pivoted no at some point beyond the outside products in cartridge form so as to ac- need for a 16 -inch table, and few of the record, and thus the stylus moves commodate the user who wants a car- would have the space available for such on the arc of a circle. With a straight tridge that will play in a record changer. a model. But the performance of arm, introduces the this tracking error, in Some models, however, are designed to typical hi -fi turntable comes close to addition to not following the original operate with a very low stylus force, being adequate for professional work. cutting stylus movement. The bent or and consequently do not have sufficient Rumble is held offset arm to low values, with a eliminates this difficulty to a lateral component of force to actuate the minimum of 40 db signal -to large extent, since by proper -noise ratio design of changer trip mechanism. The minimum being acceptable for critical use. This angle and overhang, the tracking error stylus force that will actuate a changer figure is determined may by measuring the be kept to a maximum of 2 to 4 trip reliably is about 6 grams, so such signal from a constant -tone degrees throughout most of record of the surface pickups as Leak, Weathers, and the known stylus velocity and then measur- of a 12 -inch record. Tracking error is Electro -Sonic professional are denied to ing the signal from an unmodulated the angle the axis of the pickup makes changer users. Each of these manufac- groove with the same with a settings of the tangent to the groove at the point turers provides his own type of arm, and controls. A low -pass filter of contact with the stylus. cutting off Overhang is performance of arm and,pickup together at not over 500 cps is desirable for these the distance . the stylus extends beyond is considered good in all those models. measurements, using 400 the center of the turntable spindle. This cps for the The Leak arm is a simple tube, counter- constant tone so the filter does not affect is usually of the order of to 34 in., weighted at the back, and equipped with response at that frequency. and is comparatively critical. Some man- a receptacle into which the pickup is The NARTB ufacturers specifies a stylus veloc- have made ingenious tem- plugged. The arm pivots in both planes ity of 7 cm /sec as the plates to ensure locating standard. This the arm accu- on a single vertical pivot, and is held is an unrealistic value because practically rately with respect to the turntable in place laterally by a bracket which any phonograph record today will be center so that tracking error will be straddles the vertical pivot. The leads recorded to a velocity maintained at minimum of 15 to 20 cm /sec. a value. from the pickup are carried through the Signal -to -noise ratio -or the measure- While it might seem logical to arrange mounting stud where they terminate in ment of rumble-should be related to carry the pickup a female receptacle to along a radius of at the lower end of the normal maximum signal that is the record, this is a difficult problem the stud. played through the with system, so we take conventional turntables. If a typical The Weathers arm is made of balsa the stand that a reference of 20 recording wood, cm /sec. lathe were used for reproduc- suitably reinforced, and styled for should be used. This is approximately tion, it would only be necessary to mount good appearance. Balsa wood is light 10 db higher than the NARTB standard, the arm selected on and a bracket carried on free from natural resonances, and but we feel that it is more realistic in the moving carriage of the recording consequently is a good material for this view of today's practices. machine. Since purpose. a good recording lathe The ESL professional arm is The most convenient mechanism of this type usually costs several a long counterweighted for times tube with a slight playing phonograph records is what the better hi -fi system does, offset near the head mounting. the this All of changer. These have reached a high seems like an impractical solution. It these arms are suitable only for use with degree would eliminate the of development, and many fea- the problem of tracking manufacturer's pickups. tures which add to error entirely, and would, the pleasure and ease furthermore, Most modern arms have provision for of playing records have been move the pickup in exactly all types of incorpo- the same cartridges -the few excep- rated in current models. The modern manner that the cutting stylus was tions that will not fit into the standard moved. changer handles records with care, drops One device designed to move mounting dimensions are Audax, Leak, them gently onto the pickup along a radius professional, an air cushion, posi- has been shown ESL and Weathers. Adapt- tions the pickup over the run recently, but it does not ers are -in grooves, appear to have available for fitting the Audax and lowers the stylus more gently achieved much acceptance so far pickups to most changers, than in and the ESL the average user is likely to. And while spite of the obvious advantage in theory. models which will work properly in To overcome the manual handling of the pickup arm the friction of such a changers are designed to fit standard can be as gentle mechanism by heads. as possible, human means of an infinitesimal Plug -in heads for changer arms frailty is a factor and contact between stylus make it simple no one will always a and a groove, a matter to change pick- position the stylus over a run with a stylus force of 6 ups when -in groove to 8 grams hold- desired, such as from a 78 (so as to avoid damage to the first re- ing the stylus in the groove, does seem pickup to an LP model when a turnover like corded grooves) and no one will always an almost insurmountable problem. type is not being used. lower the stylus A separate motor drive gently. The chànger, calibrated to being governed by mechanical stops, indicate lines per inch might be a possi- Turntables and Changers cams, ble and the like, will perform the solution, but the cost would undoubt- Although perhaps the first item same operation over edly be prohibitive. to and over in exactly be considered in setting up a phonograph the same manner. For general listening, Unless a straight arm is of infinite system is the means whereby the record the changer is by far the most convenient length, there will be some tracking error. is rotated, the turntable itself is being record playing mechanism. and the average hi -fi equipment cabinet considered last. The range of equipment Next in order of convenience is the will not accommodate an arm of infinite in this category is large -with broadcast automatized record player. Some of these length. Literally dozens of patents have turntables in their own console cabinets do everything a changer does except been granted for arms which were costing several hundred dollars down to actually change records -that is, they claimed to eliminate tracking error by the lowly two -pole-motor- turntable start, lower the pickup to the record at some arrangement of arms and levers, which can be purchased from bargain the proper place, shut off after playing but only one of these has ever appeared counters at less than five dollars. There and return the arm to the rest. Still to gain a foothold. This is the B -J arm, is a difference, of course. simpler is the player in which the arm is

AUDIO JUNE, 1955 33

www.americanradiohistory.com positioned manually, but is coupled to accessory items are described in the the motor switch so as to be, in effect, following pages. the switch handle. These, too, have Note: In comparing the ouput voltages reached a high standard of performance, from the pickups in the following listings, and rumble, wow, flutter, and external all values have been related to a stylus hum field have all been reduced so that velocity of 7 cm /sec, which is likely to be they are about on a level with the better about average for commercial records. changers. The user's choice must depend Manufacturers' specifications differ in the on cost, size, and convenience of oper- reference velocity, but all are standardized ation he buys the product of any in this listing. -once in parentheses following he The KS numbers of the reputable manufacturers may the manufacturers' names and addresses are expect to obtain satisfactory performance for convenience in requesting further infor- in keeping with his requirements. mation on the Reader Service Card following page 80. If you wish any further infor- Accessories mation about any of the products described, circle the manufacturer's number, fill in Many accessories are available for your name and address, and mail -no the record collector's convenience. He postage is required. may want to protect his records by the of plastic sleeves ; he may want to use D -L -6, -static PHONOGRAPH PICKUPS Audak cartridge. All models -R -2, reduce static by some form of anti and HI -Q7 are of same appearance. solution which he may either wipe or Angel. Kingdom Products, Ltd., 23 Park spray on the record; perhaps he may Place, New York 7, N. Y. (KS -11 gives high compliance. The stylus is one of find it desirable to employ the mounted well the front of the unit ionizes the One of the most recent pickups to be to radioactive devices which and is thus readily visible for cueing the and introduced in the U. S. is the Angel, a air near the record surface thus record to a specific place. Output volt- Whatever he product of EMI, British manufacturers neutralizes static charges. age is approximately 20 mv for the want, he is likely to find who also make the Angel Records, and is likely to D -L -6, and 30 mv for the Hi -Q7. Stylus offered. In most instances, he will have do the recording for many of the important foreign record labels. The assemblies are replaceable in seconds, to decide whether these products are making it possible to change them at of value to his own habits and customs Angel pickup was designed primarily for professional use, which is no bar to home without special tools. For use on in record collecting and playing. Some transcription -type turntables, the Audak means of determining the stylus force is arm provides ideal mounting for the a very desirable addition to the complete pickup, with its simplicity of construc- system, and the critical user should be tior and freedom of motion. For use on so equipped so he may make sure that changers, various adapters may be ob- is adjusted for his equipment properly tained to accommodate the Audax maximum performance and minimum models. record and stylus wear. Some of these

New Angel EM I pickup and arm. Arm is oil damped to retard violent movement of pickup.

New customers are constantly home use -rather, if the unit is suffi- requirements of who ciently good for the coming to us ... people broadcast and recording use, many have seen ads and articles by home users would consider it eminently We feature the GARRARD experts, recommending the suitable for their purposes. The pickup employs the moving coil RC80 Record Changer in GARRARD RC80 Record design, and is used with a step -up trans- many of our recommended Changer. We sell only those former to match 200- or 600 -ohm lines, or to match a grid. The impedance of nationally known products Hi -Fi systems. This indicates the pickup itself is 1 ohm, and the out- which live up to our high put is approximately 100 mv (on the how highly we regard this fine standards and their own grid side of the matching transformer) instrument. Having sold thou- for a recording level of 7 cm /sec. Fre- advertised claims. For this quency response extends from 20 to 20,- sands in the past few years, reason, our preference is the 000 cps with the standard stylus, and we know from experience from 20 to 16,500 cps with the micro- GARRARD RC80 "World's groove stylus. The unit is normally that we can unhesitatingly Finest Record Changer ". Listen furnished with its own arm, which em- feature the GARRARD ... then order yours, from ploys a unique suspension system to maintain constant stylus force for vari- RC80 "World's Finest Rec- ous heights of the pickup above the ord Changer ". Sold at . 1 turntable. Audak Company, 500 Fifth Ave., New York 36, N. Y. (KS-2) ALLIED Utilizing the principle of a magnetic Specialists in Hi -Fi for home or vane which relays the flux from the radio Corp. office. 820 W. Olympic Blvd., magnet poles to the core of the coil, these models -D -L -6 and the higher Los Angeles, California output Hi- Q7-are similar in design. 100 N. Western Avenue, Richmond 7 -0271 Both employ an extremely narrow sus- Chicago, Ill. i pension for the stylus bar which eliminates needle talk to a large degree, and HAymarket 1 -6800

34 AUDIO JUNE, 1955

www.americanradiohistory.com Electro -Sonic Laboratories, Inc., 35 -54 Ferranti Electric, 30 Rockefeller Plaza, 36th St., Long Island City 1, N. Y. (KS -3) New York 20, N. Y. (KS -6) These cartridges are electrodynamic This model, designed by D. T. N. devices built precisely like a tiny Williamson -best known for the design D'Arsonval meter movement. A rec- of an amplifier which is widely copied tangular coil of very small dimensions -employs a low -mass high -compliance is held vertically in a strong magnetic ribbon movement. Another unusual fea- field. One end of the coil mounting is ture of this pickup is the use of an ellip- fastened to a stylus shoe so that the tical stylus which is so placed that its major axis is perpendicular to the record groove. This reduces the effective Fairchild Model 220 is latest cartridge in radius of the stylus tip and more closely this line, which is a popular moving coil - approximates the shape of the type. cutting stylus, which is invariably of a chisel shape. This shape increases the ability cm/sec stylus velocity. The construc- of the stylus to follow the high -fre- tion of the pickup consists of a moving quency variations in the groove better coil supported on a mylar vane between than a spherical tip, and improves trac- two pole pieces, the stylus being at- ing appreciably. tached to an aluminum arm which is The Ferranti pickup is intended for effectively an extension of the axis of use in its own arm, and is not adaptable the moving coil. High -frequency reso- for use in record changer arms nor in nance has been reduced practically to other models. The Ferranti arm features zero so that response extends essentially a double ball race arm bearing, and is flat to 17,000 cps and rolls off gradually equipped with a built -in rest. Arm re- beyond. While output is slightly lower sonance is out of the audible range. Electro -Sonic Laboratories' Concert and than most pickups on the market, the Standard models of moving -coil pickups. better modern amplifiers have low -noise General Electric Company, Electronics Park, lateral excursions of the stylus cause first stages and sufficient gain to accom- Syracuse, N. Y. (KS -7) the coil to rotate in the magnetic field. modate the 220 perfectly. The Fairchild Undoubtedly in more general use With this arrangement, the conductors amplifier employs a cascode input stage than any other pickup on the market for cut the field at right angles and develop which is especially suitable for use with high -fidelity reproduction, the G.E. car- a signal voltage directly proportional this cartridge, but it will perform satis- tridges have made it possible for a mag- factorily to the velocity of the stylus, and the with any good amplifier. netic pickup to be within the range of pickup is insensitive to vertical motion. the lowest budget, and without sacrific- The ESL pickups have an impedance of Fentone. The Fenton Company, 15 Moore ing quality. The design consists of two 1.5 ohms, and require a transformer. St., New York 4, N. Y. (KS-5) coils mounted vertically at the front of Three models of pickups are available This unit, soon to be distributed gen- the cartridge with pole pieces extend- -the standard series, which will per- erally, is imported from Denmark, and form satisfactorily in record changers; is manufactured by Bang and Olufson the Concert series, with greater com- Laboratories. It is a low impedance pliance, and designed for use with high- model-530 ohms at 1000 cps, with a d. c. resistance of 350 ohms -with sufficient output that a matching transformer is not needed. The unit uses 8 Our reputation depends on poles, and is so constructed as to mini- reliability. Prompt service and spare parts must always be available. That's why we generally install the GARRARD RC80 Record Changer. In fifteen years of dealing with this manufacturer, we have always Professional model of Electro -Sonic Labo- found them willing and able ratories' pickup with arm (with which it to stand behind their prod- must be used.) uct. Therefore, we endorse quality arms; and the Professional the GARRARD RC80 series which comes with its own arm The Danish -made Fentone pickup. "World's Finest Record and is intended for purely professional ". applications. Several types of trans- mize hum pickup from motors or power Changer It's always in formers are available for differing re- transformers. The stylus compliance is stock at quirements. relatively high -5 x 10-e cm/dyne, and the equivalent stylus mass is 4.5 mg Fairchild Recording Equipment Co., 154th for the dual ARROW St. and Powells stylus and 3.5 mg for the Cove Rd., Whitestone 57, single- stylus model. N. Y. (KS-4) Frequency response ELECTRONICS is claimed to be flat from 20 to 16,000 The new 220 series cartridge is de- cps ± 2 db, with a gradual rise to over signed to. mount in all standard arms, 20,000 cps. The output voltage is approx- and has an impedance of 170 ohms, imately 50 my for the standard stylus which is almost purely resistive in na- velocity of 7 cm /sec, and the pickup ture, which makes it possible to operate tracks with a stylus force of 5 to 7 with a relatively long shielded cable grams. It is available with two sapphire "Always an Audio Fair" between pickup and grid, and with styli, or with a diamond-LP stylus and 65 Cortlandt Street, practically any grid resistor. Rated out- a sapphire 78 stylus, or in single -stylus put is of the order of 5 my for a 7 models with either sapphire or diamond. New York City

AUDIO JUNE, 1955 35

www.americanradiohistory.com ..a:f -1 ..t*` -`.a.7ktl!4Wyy,.ÿ

rotatable channel in the case of the double- stylus models, or out of a fixed channel in the single -play cartridges. This permits the user of a single -stylus cartridge to change from LP to 78 hrost as easily as though it were a two- stylus model, yet with the economy of the single -stylus cartridge. All future models of the GE pickups will be produced with the new "Clip -in Tip" feature.

Leak. British Industries Corporation. 16-1 Dunne St., New York 13, N. Y. (KS-8) Another moving -coil pickup which ha, achieved an excellent reputation, par- Latest model of G. E. Triple Play cartridge 260 employs two single in England since it has not been Pickering model has simplied method for changing styli. ticularly cartridges in turnover mounting. widely distributed in the U. S. to date, is Leak. It is in common use by the ing down to each side of the stylus the of 4 to 8 grams stylus force. Those who BBC, and is used considerably in re- arm. A cylindrical permanent magnet have no need for both pickups can use studios for dubbing and play- provides the field, and the magnetic cir- cording either model separately with an adapter cuit includes the stylus bar, two pole clip. pieces, the coif yokes, and the magnet. In construction. the Pickering cart- Several types are available -with either ridges consist of a nickel tube which is single or double stylus, and with sap- positioned in the center of a coil and phire or diamond as desired. The Gol- subjected to a magnetic field, the stylus den Treasure models have a diamond being fixed at the lower end of the tube. LP stylus and a sapphire 78 stylus in a Movement of the tube within the coil dual assembly which is readily replace- causes a change of flux which generates able, and which is changed from one to the signal voltage. At the standard veloc- the other by a knob at the to of the ity of 7 cm/sec, the output is of the order cartridge. The miniscule Leak pickup on its own (,i 22 my, and frequency response is flat A recent improvement in the mount- arm. 78 model is weighted slightly so no ing provides for the replacement of change of adjustment is required when either stylus independently without the pickups are changed. need for replacing the entire assembly. The stylus is carried on a "Clip -in Tip" back. The newest model -which is nearly which simply slides in or out of the two years old -is essentially the same principle as its predecessor, and consist - of a rectangular coil which is mounted in the field of a permanent magnet. The rea- axis of the coil is approximately tangent There are many good to the record groove. The coil itself i> sons why our customers wound on a plastic former, and offers a prefer the GARRARD minimum of mass and a very high compliance, as indicated by a high -frequency RC80 Record Changer. resonance of 21,000 cps ±2000 cps with Convenience seems of par- the LP stylus on a Vinyl pressing, and amount importance ... all with the 78 stylus on shellac pressings Single Pickering units may be used sepa- the resonant frequency is above 27,000 rately in special clips. the way from easy installa- cps. Low- frequency resonance with the tion with exclusive snap -in Leak arm is at approximately 20 cps. on a velocity basis over the range from spring mountings, which Using the step -up transformer fur- 20 to 20,000 cps. The cartridges are top nished with the pickup, the output is ap- available only with diamonds for LP can be levelled from the roximately 70 mv from a stylus velocity use, and with a choice of diamond or ... through quick wiring of 7 cm/sec. Additional weighting in the sapphire for 78's. with the cable and UL ap- pickup head makes it unnecessary to ad- proved cord ,attached, they just needle force when the heads are Recoton -Goldring. Recoton Corp., 147 W. changed. The arm is mounted through a 22nd St., New York 11, N. Y. 1 KS -10) the refinements connections are appreciate single hole, and electrical Another imported cartridge which is a small receptacle in the they get in the made through likely to make a name for itself is the bottom of the mounting stud. GARRARD RC80 Recoton -Goldring model 500. Not uncon- ventional in design, this. unit features a "World's Finest Record Pickering Cr Company, Inc., 309 Woods hum -bucking coil construction, replace- Changer ". See it at your Ave., Oceanside, N. Y. (KS -9) able styli, and a turnover mounting earliest convenience, at The first magnetic cartridge to be which may be fitted into practically any ... placed on the market for replacement standard arm. The stylus assembly for purposes, the Pickering introduced many each "half" of the pickup consists of a listeners to the advantages of high -qual- cantilever mounting which is removed ity reproduction for the first time, and simply by taking one screw out. With it has long held its position of esteem completely separate moving parts, there amongst discriminating listeners. The is no interaction, and the idle stylus has current model is the 260-which consists no effect on the one that is "working." of Detroit's High Fidelity of a 240 series LP pickup and a 220 Essentially, however, the unit consists series 78 pickup mounted in a turnover a single stationary assembly which ac- Headquarters, styli. It is designed to 7422 mechanism which shorts out the unit commodates two Woodward Avenue, that is not in use. The 260 weighs 18 work into a 47,000 -ohm resistance, and Trinity 4-1100 grams complete, and tracks over a range has an output of approximately 22 mv

JUNE, 1955 36 AUDIO

www.americanradiohistory.com and a frequency range which is virtually and power supply, or as a complete rec- flat from 20 to 16,000 cps. Lateral com- ord player (except for power amplifier pliance is stated to be 4 x 10-6 cm /dyne, and speaker). and the effective mass at the stylus tip is 3.5 mg. It will track with a stylus CRYSTALS AND CERAMIC force of 3 to 4 grams with a high -qualit PICKUPS arm, and at 6 to 7 grams in most record changers. Astatic Corporation, 250 Harbor St., Con-

neaut, Ohio. . (KS-121 Weathers Industries, 66 E. Gloucester Four models of cartridges are offered Pike, Barrington, N. J. (KS-111 by ,Astatic for high -fidelity use-two Employing an entirely different prin- with ceramic units and two with Rochelle ciple of operation than the pickups de- salt crystal units. All four are compen- scribed in the foregoing, the Weathers sated to match the RIAA curve approxi- pickup will track with a force of 1 gram, mately and require no further equaliza- Electro -Voice series 80 cartridges are now -6 has a lateral compliance of 14 x 10 tion in the amplifier. The ceramic models zvailable as direct substitutes for magnetic cm /dyne, and an effective mass at the are 51 -IJ with a single stylus, and models. stylus tip of 1 mg. Part of this is the result of the method low -frequency response from the pickup, of operation, for the Weathers pickup is and the bass -boost characteristic of the a device which varies the capacitance of amplifier promptly makes up for it. This the unit in accordance with the groove permits the user to make a direct replace- modulation, and the capacitance variation ment in cases where the characteristics produces a change in the output fre- of the ceramic cartridge may be desired quency of an oscillator. This results in -a change that would be especially de- an FM signal which is detected in the sirable in the case of incurable hum same unit as the oscillator, and an audio pick -up, for example. signal is fed to succeeding amplifier equipment. It is not susceptible to hum Ronette Acoustical Corporation, 135 Front pick -up, and the output voltage from the St., New York 5, N. Y. IKS -141 oscillator- demodulator -preamplifier unit One of the first crystal pickups to make is of the order of 2 or 3 volts and does a reputation for high reproduction qual- not require equalization. Thus the signal Astatic model 51-11 ceramic cartridge. ity is the Ronette, a unit imported from may be fed into the radio, tape, or TV Holland and available in a number of 55 -TJ with two styli. The former tracks input of a conventional amplifier. forms. ItIodel TO -284 is at a stylus force of 9 grams, and lat- the type number The Weathers pickup is available in the applied to the ter at 8 grams. Output with either type turnover cartridge which several forms-as a cartridge, as a com- is adaptable most is approximately 0.9 volts from the stand- to arms and will re- plete pickup system which includes car- place conventional crystal pickups in or- tridge, arm, and a combination oscillator ard reference stylus velocity of 7 cm/sec. Model CAC -J is the single -stylus crystal pickup, which tracks at a stylus force of approximately 6 grams, and which gives an output of 0.6 volts. The dual -stylus New record changers are crystal unit is the CAC -D, which gives When an output of 0.4 volts, and requires a constantly coming on the it comes to record stylus force of 10 grams. market, but we think the changers, there's only one Electro- Voice, Inc., Cecil and Carroll St., GARRARD RC80 stays at for us... the GARRARD Buchanan, Mich. (KS-13) the head of the line in engi- RC80. We feature it on the Two models of ceramic cartridges are cover of our catalogue? Our currently available -the 84 Ultra-Linear neering advancements. experts say that for which was one of the first to match the Here's the leading hi -fi con- RIAA curve without external equaliza- stant speed, lowest rumble tion, and the new Series 80 which has changer...with a tried and and hum, highest all - just been introduced. The 84 has an out- true basic design proven around performance, the put voltage of approximately 0.5 volts from the standard stylus velocity of 7 through millions of hours standout changer contin- cm/sec, and works best into a load re- ues to be the GARRARD sistance of 3 megohms. It has a compli- of actual play. RC80 "World's ance of 1.2 x 10-8 cm /dyne, and a mini- The GARRARD RC80 Finest Rec- mum of vertical pick -up. As with any ord Changer ". Check it and ceramic cartridge. there is no hum pick- "World's Finest Record hear it at up from magnetic fields, and when Changer ". worked into the specified load impedance, the output curve follows closely that of You can hear it at - the RIAA curve. The new Series 80 has approximately the same output, but has ELECTRONICS RADIO SHACK CORP. increased compliance -the figure stated by the manufacturer to be 3.0 x 10-6 W HOLESALERS cm /dyne. The 80 series is available in Our 32nd year of leadership. several forms, each designed to work 167 Washington Street, into a conventional preamplifier intended INC. Boston, Mass. for magnetic pickups without modifica- LAtayette 3 -3700 tion. Thus the pickup may be had to For Everything In Audio, and 230 Crown Street, work directly into an amplifier designed New Haven, Conn. to accommodate either G.E., Pickering, 2345 Sherman Avenue, N.W., Fairchild, or Audak cartridges, with the ashington 1,D. C. Hudson 3 -5200 lower load impedance of the input stage of the preamplifier serving to reduce

AUDIO JUNE, 1955 37

www.americanradiohistory.com dinary inexpensive phonographs. TO- cartridge and still retain the advantages provide an output signal of slightly more 284-6V is a high -output model designed of the variable turnover and rolloff char- than 1 volt. When worked into a 5 -meg for direct replacement in equipment de- acteristics of a conventional preamplifier. load, the response is flat within t 2 db signed for crystal pickups. It works into The Ronette is claimed to have the low- from 30 to 15,000 cps. Compliance is ap- a load resistance of 0.5 meg, and has est intermodulation distortion of any proximately 1 x 10-6 cm/dyne. Both mod- somewhat more low- frequency response pickup on the market. The arm is neatly els of cartridges are available for mount- than the other types. The output voltage styled, and provides extremely low drag, ing on standard pickup mounting centers, from a 7 cm /sec stylus velocity is ap- being mounted on ball bearings. Stylus or with no brackets for installation in proximately 1.5 volts, and the pickup will force is adjustable by means of a screw narrow heads. track with a needle force of 6 to 8 grams. from 1 to 8 grams, and the head permits r TO -284 -N is the standard type car- turning the cartridge to a half -way posi- PICKUP ARMS where both styli from tridge for use with normal domestic tion are protected of pickups accidental damage. While most manufacturers are reluctant to entrust the final per- Shure Brothers, Inc., 225 W. Huron St., formance of their product to an arm Chicago 10, Ill. (KS-15) made by another manufacturer and, consequently, provide an arm of their own In addition to a large line of standard design which should give optimum per- quality phonograph pickups made for the formance with their own product, there phonograph trade, Shure Brothers also are some arms available that have special manufactures some models intended for characteristics which are claimed to high- fidelity use. The most recent of make them ideal for all pickups. In many these models is the "Balanced Fidelity" instances, the arm provided by the pickup "Twin Lever" ceramic, which offers ex- manufacturer may also be used with cellent response-tailored practically to other cartridges -either with or without match the RIAA curve without equali- adapters -and these types are listed here zation in the amplifier relatively Holland -made Ronette is hi -fi crystal not -and along with the arms sold for general use. ceramic, pickup of high compliance. high output voltage. The "Twin Lever" feature is the stylus assembly, which is Audak Company, 500 Fifth Ave., New radio receivers and small amplifiers. Its composed of a replaceable mounting plate York 17, N. Y. IKS -2) to which two parallel stylus output voltage is approximately 1.0 volts. are attached The Audak arm is especially designed Both the above models are designed to arms approximately A in. apart. At the outer ends of these arms the styli are to accommodate the Audax Chromatic provide approximate compensation for at- pickups, but with an adapter may be the RIAA recording curve. tached, and suitable damping material is The arm located between the arms. The "turn- used with any standard pickup. Model TO -284-P is the professional is of simple construction, having only type of cartridge, and is designed to over" mechanism lifts both arms to- work into a load restistance of 0.12 meg. gether, positions the desired stylus over With this load, the response is that of a the coupling lever to the ceramic ele- velocity-sensitive pickup, and it should ment, and lowers it into a notch on the be worked into a standard type of pre- lever. Both styli are replaced at the same amplifier designed to provide the bass time without tools, and the unit is in- boost required for magnetic cartridges. geniously designed. This model tracks Its output is approximately 0.3 volts at with a stylus force of approximately 6 Audak arm is designed for Audax Poly- 1000 cps, and since this is considerably grams, and the output signal is of the phase pickup, but adapter is available for greater than most magnetic pickups, a order of 0.5 volts at 1000 cps from a use with other pickups. voltage divider may be required ahead of stylus velocity of 7 cm/sec. the first tube to avoid overloading. Most three moving parts -the base, with a preamplifiers have an input impedance Sonotone Corporation, Elmsford, N. Y. long pointed pivot, the rotating section of the order of 47,000 ohms -the highest (KS -16) which seats over the pivot like a com- load value required by presently avail- pass needle, and the arm, which is piv- Two models of Sonotone Ceramic car- oted horizontally 2 in. in front of the able magnetic pickups-and the required tridges are available -model 1P which 0.12 meg load may be had by adding a vertical pivot. The rear of the arm is has a single stylus (1 -, 2 -, or 3 -mil sap- counterweighted, and current models 75,000 -ohm series resistor, which will re- phire or 1- or 3 -mil diamond), and model 2T which is equipped with two styli in a turnover arrangement for playing both microgroove and 78 recordings.

Adapter to permit mounting any pickup Ronette arm is compact, neatly styled. on Audak arm. duce the input voltage at the same time provide for stylus force adjustment. The to about 0.1 volts (100 mv) and should adapter fits into the Audak arm and ac- eliminate the first -stage distortion. If not, commodates any standard cartridge. the input resistor can be shunted with 39,000 ohms, which reduces the effective B -J Arm. Hi- Fidelity Incorporated, 420 21,000 M, Bison Ave., New York 17, N. Y. input impedance to approximately IKS -17) ohms. With a 0.1 -meg series resistor, the required 0.12 meg load is obtained, and This arm, developed by Mr. Burne- the input signal is reduced to approxi- Typical Sonotone ceramic cartridge. Jones, was designed to maintain the axis mately 50 mv, which should not overload of a pickup tangent to the record groove any modern amplifier. Both pickups have an internal capaci- throughout the playing area. While a In cases of excessive hum pick -up, this tance of approximately 450 µµf, track simple pivoted arm would need to have is an ideal way to replace the magnetic with a stylus force of 8 to 10 grams, and infinite length to provide the tangent

38 AUDIO JUNE, 1955

www.americanradiohistory.com Here's the turntable professionals want in their own Hi -Fi setups t, o

the all -new PRESTO T -18 streamlined inside and out ... delivers top professional performance with incredible ease of operation 12" diameter ...only $53.50 with hysteresis motor, $108

... and here's the 16" version Nobody knows better than the hi -fi expert how good the for home or professional use 1 T -18 turntable really is. T -18 fills your every requirement PRESTO T -68 TURNTABLE for performance and value... is a natural choice for your home, as well as your studio and control room. The first completely professional 16" turntable The most exciting feature of PRESTO's T18 is a revo- :hat's moderately priced - thanks to PRESTO's ,treamlined shift design. Like all PRESTO units, lutionary 3 -way shift - the flick shift. A simple sideway T -68 offers the reliable performance that is vital motion of the single control lever selects any speed - in 24- hour-a -day transcription work. It's ideal 331/3, 45, 78 rpm. Complicated up- and -down motions are for disc programs, sound effects, client auditions, eliminated because the 3 idlers are mounted on a single dozens of jobs ...and it's wonderful for the home movable plate. Just a flick automatically engages the with a fine hi -fi collection. proper idler for the desired speed! There are no trouble- T -68 specifications: turntable speeds - 33'ía, making arms or shift cams. The mechanism is streamlined 45, 78 rpm weight -7 lbs. panel down to essentials- without sacrificing a decibel of quality. size - 8" x 11" speed accuracy - max. variation 0.25% clarity -- Other advantages - extra heavy weight wide -beveled 50 db below 7 cm /sec. signal table, precision deep -well bearing, built -in 45 rpm adapter, $79.50 with hysteresis motor, $134. and smart modern styling in brushed chrome and telephone black. A remarkable hi -fi instrument!

Ij1 RECORDING CORPORATION PARAMUS, NEW JERSEY

Export Division: 25 Warren Street, New York 7, N. Y. Canadian Division: Instantaneous Recording Service, 42 Lombard Street, Toronto

WORLD'S LARGEST MANUFACTURER OF PRECISION RECORDING EQUIPMENT AND DISCS

www.americanradiohistory.com tracking, it is possible by the ingenious force. and tightened in place. The range contact with the groove at the high spots method used in the B -J arm to reduce of weights is such that the arm will ac- in the record, causing distortion under tracking error to less than 1 degree from commodate pickups from 5 grams up to optimum conditions, and groove jumping beginning to end of a 12 -in, record. An at least 2 ounces. Height of the arm is in worse cases. Thus the Fairchild arm analysis of the geometry of this design also adjustable, and the horizontal pivots has considerable effective mass in the proves the claims of the manufacturer are needle pointed. Models of this lateral plane, but because of spring - -to be accurate. The pickup consists of a arm are also available with a slot which aided suspension has somewhat less in mounting base which is fixed, two arms accommodates the turnaround knob of the vertical plane. These features result pivoted independently in the top of the the type used on the G.E. cartridge. in a minimum of distortion due to the mounting base with their pivots approxi- Tracking error at the center of a 12 -in. arm alone. mately 2 in. apart, and pivoted on 1 -in. record is practically zero, and rises to a The cartridges are carried on a maximum of 6 deg. at the outside "drawer" in the Fairchild arm, and can grooves. he replaced instantly, providing each cartridge is mounted in a separate drawer. Fairchild Recording Equipment Co., 154th When the drawer is removed, the spring and Powells Cove Rd., Whitestone 57, contacts short together, preventing an N. Y. (KS-41 open circuit hum while the cartridge is The design and construction of a taken out of the arm. The height is easily pickup arm is of considerable importance adjustable, and stylus force is adjusted by a screw on the bottom of the arm. B -1 arm maintains tangency to record to the performance of the pickup itself, groove at all diameters. particularly in the very low frequency The arm -the 280 series -is available region and occasionally in the range in two lengths, one for 12 -in. records, centers at the pickup head. The head will and the other for 16 -in. transcriptions. accommodate any standard cartridge, and stylus force is adjusted by adding or re- General Electric Company, Electronics moving lead weights underneath the top Park, Syracuse, N. Y. (KS -7) section of the mounting base. The two Two models of arms are offered by arms are of different length, and conse- G.E. to accommodate 12- and 16 -in. quently have different resonant frequen- discs. Both are of aluminum construction cies, which is said to reduce low -fre- to offer a minimum of lateral and verti- quency resonance. cal inertia. These models consist of a mounting base with the vertical bearing, Clarkstan Arm. Pacific Transducer Corp., two parallel aluminum tubes serving as 11921 W. Pico Blvd., Los Angeles 64, the arm and terminating in the horizon- Calif. (KS -18) tal bearing, and a cartridge head which The Clarkstan arm is especially suited will accommodate most cartridges. The for the experimenter who has occasion head tilts upward 90 deg. for easy stylus to change pickups often for one reason Fairchild 280 arm has high inertia in lateral or another, because the method of chang- plane, low in vertical. ing- and the ease with which the stylus force can be readjusted makes it a most from 100 to 200 cps, the former being convenient arm for this purpose. Avail- the resonant frequency between the com- able in two lengths, these arms are of pliance of the pickup and the mass of the cast aluminum construction, and have an arm, while the second is the effect of open channel at the pickup end which is torsional resonance in the arm itself. of the correct width to accommodate Careful distribution of weight and ad- most modern cartridges. A thumb screw justment of compliances can reduce the -which also serves as a lifting handle- effects of these resonances to a mini- General Electric "Baton" arm has easily tightens a flat spring against the pickup mum. For example, it is desirable to have adjusted weight: arm hinges upward for to hold it firmly, while silver -plated a large mass acting on the arm in a hori- stylus inspection. spring- loaded plungers maintain positive zontal direction but considerably less in If record inspection, and when in the operating electrical contact to the pickup terminals. the vertical plane. turntable and an arm The weight adjustment consists of a were perfectly level, a very heavy arm position is counterweighted by to the two round button held in counterweighted be which extends back parallel counterweighting -suitably -would which a place by a captive screw which slides in ideal, for the resonance of arm and aluminum tubes, and carries is directly a slot in the arm. To change the weight, pickup would be at a very low frequency. sliding weight. The calibration in grams when used with a G.E. car- the button is loosened, moved to the posi- However, records are not always per- vertical bearings tion which provides the correct stylus fectly flat and the stylus may tend to lose tridge. Both lateral and use precision ball races which are dust proof and lubricated for limetime use. The bottom of the mounting base is slightly curved to permit levelling by the "SOUND" ADVICE three screws which affix it to the motor 1) Read G. C. McProud's hoard. "Equipment Report" on the four outstanding PE Gray Research and Development Company, Rex changers in the May Inc., Manchester, Conn. KS -19' issue of Audio. lyy front 2) Get the new be Two types of arms are available Low -Z magnetic cartridge Gray -the 106 and the 108 series. The for Beautiful & Qutstanding performance. 106 models are precision instruments The cartridge simply snaps out of its made to provide a complete range of ad- standard American mount, permitting justment and using precision ball bear- actual test of your cartridge at the point ings for both vertical and horizontal of purchase. pivots, with cone point adjustment to en- Write for descriptive literature. sure minimum friction without excessive FENTON COMPANY play. The arms are equipped with level- 15 Moore Street, ling screws, and the stylus force may be New York 4, N. Y adjusted by the knurled thumb screw shown adjacent to the scale. Slides to lit

40 AUDIO JUNE. 1955

www.americanradiohistory.com for those who care

Ilf enough to hear the Gray 106S arm offers precision workman- ship, ease in adjusting stylus force. very most cartridge types are available, and slip into the end of the arm, making electrical contact at the same time. The best earlier 103 arm was designed for fixed cartridge use, and was not equipped with the readily changeable slides. Another Gray development is the vis- vs, cous damped arm. Damping aids in sup- pressing any resonances of the arm by introducing mechanical resistance into the mechanical resonant circuit. The methods of obtaining linear mechanical resistance are limited, but the method employed in these arms is simple and I7A effective. In construction, these arms consist of a conical pivot which supports the arm just free of contact between a convex spherical surface on the arm and NIPIVOT TRANSCRIPTION PICK -UP

Mc de at Hayes, England by the manufacturers of

A new experience in crisp, clean, natural sound awaits you when you hear your favorite records reproduced with the Angel -the Ann with the "Heavenly Touch "! ... A precision instrument with pickup and arm completely integrated for the finest reproduction of both microgroove and standard records. Its frequency response covers the entire audible recorded range, from 20 to 16,500 cps. with microgroove stylus, 20 to 20,000 cps. with standard stylus. The ANGEL ARM is suspended on a single pivot, viscous- damped for perfect freedom of movement both horizontally and vertically. It is modern and attractive in design, sturdy in Cray 108C arm is newer, lower priced, but construction ... provides perfect tracking . , . only 6 grams at the stylus point insures a mini- still employs viscous damping. mum of both record and stylus wear. Accommodates all records up to 17" transcriptions. Engineered for professional use and for true music lovers who demand the ultimate in a concave spherical surface on the base. record -playing perfection. The space between these spherical surfaces is partially filled with a silicone oil -a product which maintains a practically constant viscosity regardless of temperature. The thickness of the oil film is controllable by the user by a simple adjustment of a thumb screw on the top. The damping also helps to protect UNIPIVOT FLOATING ARM CANTILEVER MOUNTED STYLUS TRANSFORMERS records because of its retarding action. Prendes viscosity oil damping in hori Essential for extremely high fidelity Two types are available for adaptation In case the arm is dropped accidentally I and vertical directions ... pre reproduction of m crogroove ecords. of PICKUP to required amplifier cir. Penis a cidental dropping. Pertesr Balanced weight prolongs stylusr lile... cuits. Rotating mount permits installs. over the record, the pickup falls gently to heedom c of arm ent eliminates reduces tracing distortion. Plug -in head tion at minimum external not e- piekup. the surface of the disc, and does not .. e end groove e lumping, reduces permits ropid interchangeability of dia. rcc .,rd s wear. mond stylus for microgroove and sap. bounce up and down on the record sur- phire stylus for standard records. face. MODEL 17A - ANGEL ARM MODEL 78 - Standard 78 RPM Pick-up, with Sapphire Stylus $12.50 Pickering b Company. Inc., 309 Woods Supplied complete with LP Cartridge Diamond s895o Ave., Oceanside, N. Y. (KS -9) Stylus, High Impedance Transformer MODEL 46775E - Transformer for matching 200 or 600 ohm lines $12.50 Another concept of the proper design for pickup arms is represented by the Available at oll leading distributors. For literature, write Dept. A -6. Pickering design. In this model the cartridge is carried on a pivoted plate in the KINGDOM PRODUCTS, Ltd. 23 Park Place, New York 7, N. Y. forward end of the arni. with the dis- Exclusive Distributors In U.S.A. for EMI ANGEL PICK -UP

AUDIO JUNE, 1955 41

www.americanradiohistory.com tance from stylus to the horizontal axis tective measure, the arm is installed so bearing and the motor shaft. The turn- being less than 3 in. The mounting plate that the stylus cannot come in contact table is an aluminum casting balanced is spring balanced, and thus provides a with the top of the turntable. for smooth running. The bushing for minimum of vertical inertia while the 45 -rpm records is permanently placed, lateral inertia is relatively high. This PROFESSIONAL -TYPE and is raised to operating position by meets the requirements previously dis- TURNTABLES lifting the spindle. Since the entire mounting consists of an 8 x 11 panel, a Garrard. British Industries Corporation, 164 simple rectangular hole is all that is re- Duane St., New York 14, N. Y. quired fur the in tallation, and the (KS -b0) The Garrard Model 301 turntable is a heavy -duty single -play unit which is designed for transcription use, or for those who prefer professional-type equipment for home reproduction of records. This model is furnished on a cast mounting plate of attractive design, and employs a cast aluminum turntable which is machined to extremely close tolerances.

Pickering arm; cartridge mounting plate is hinged near front and offset for proper Three separate idlers -one for each speed tracking. -couple motor shaft to turntable in Presto T -18. cussed. The cartridge is lifted by an extension of the hinged plate projecting mounting plate does not interfere with out in front of the arm, permitting it to the placement of the pickup arm. The be carried to the record and lowered in T -18 is available with either a hysteresis place. The usual arm rest is replaced by motor or with a shaded -pole motor. The a small permanent magnet in the arm G d Model 301 transcription turntable. model using the hysteresis motor is said which contacts a metal stop holds to be 10 db quieter than the other, but the and motor the arm in place. The cartridge plate is Three controls are provided -a improved performance is obtained at a offset inside the arm so that tracking switch, a speed selector, and a vernier considerable price differential. speed The is covered error is reduced to less than 2.5 deg. at control. turntable Model T-68 is essentially identical in with a ribbed soft rubber disc to provide any point on a 12 -in. record. As a pro- mechanical construction, but is equipped reliable traction without any dust -col- with a 15g-in. turntable. lecting characteristics. The motor drive is exceptionally well designed for minimum rumble and flutter, and the heavy turntable shaft is carried in adequate bearings. The GARRARD RC80 Record Changer Presto Recording Corporation, P. 0. Box We have sold more continues to be the back- 500, Paramus, N. J. IKS -21) GARRARDRI) RC80 Record bone of our high fidelity The new Model T -18 turntable- intro- Changers during the past sales. Whether the duced only this Spring -is of extremely 5 years than all other customer insists upon the simple construction. The drive incor- changers combined, and quality of porates three heavy -duty idlers, one for a professional each turntable speed. These idlers are have installed them in turntable, or prefers the mounted on shafts which are rigidly systems from $150.00 to convenience of a changer, $2500.00. In our opinion, re- we know that we can gardless of price, the best satisfy all his requirements buy in record changers for with the GARRARD RC80 any system is the GARRARDt RD "World's Finest Record R(:80 "World's Finest Rec- ord Changer ". See how it Changer ". fits your budget. Inquire by A "best buy" at mail or at uasonMO (ACM, oivututoas 114010 rrlrVIf1ON COP. Presto T -18 is one of newest models on fl1CTROMIC [ SOUND 1Q111PMINT 5000 sq. ft. of Hi -Fi the market, employs simple and effcient mechanism. demonstration rooms. 3 great sound rooms 223 W. Madison Street, fixed to a base plate, and all three are serving New York area. Chicago, Ill. State 2 -2950 identical, permitting a quick substitu- 48 tion in case of any failure, and requiring West 48th Street, California branch at 212 Fulton Street, ACORN RADIO 6 the stocking of only one idler for re- ELECTRONICS placement purposes. To select speeds, the New York City, 4736 W. Century Blvd., entire plate is moved. being pivoted about 35 William Street, Englewood, Calif. half way between the turntable shaft Newark.

42 AUDIO JUNE, 1955

www.americanradiohistory.com IRVING tiOLODIN comments on diamond phoitoraph needles:.

"Only one material

really suffices (as a

phonograph needle)

the diamond. Nothing

else matches it ..

anything else may

categorically be denied

consideration as ... high fidelity."

Pae.styke, Music Editor e--`, Saturday Review

47 WORLD'S LARGEST PLAY SAFE MANUFACTURERS PLAY DIAMOND TETRAD OF DIAMOND STYLI

Ask your dealer or serviceman for a BRAND NAME DIAMOND Record -Needle Care Folders: Dept. UC -6, 62 St. Mary Street, Yonkers, N. Y.

AUDIO JUNE, 1955 43

www.americanradiohistory.com Rek -O -Kut Company, 38 -01 Queens Blvd., sure true operation. The idler pulley is a Long Island City 1, N. Y. IKS -221 machined aluminum wheel with a bonded With the introduction of the new neoprene tire ground to a high degree of model L -37, there are now four turn- concentricity. The motor pulley is a tables in the Rek -O -Kut line that are phenolic rod pressed onto the motor designed for home playback use, in addi- shaft and then ground to size to make tion to others intended for recording and sure that it, too, is perfectly concentric. for uses that require 16 -in. models. The 45 -rpm hub is retractable, being Model B -12H consists of cast aluminum held below the surface of the turntable chassis on which is mounted a hysteresis by a bayonet catch, requiring only a motor, the idler mechanism, and the quarter turn to release it. The speed se- turntable shaft hearing. The hase plate lector knob actuates the motor switch and at the same time it places the idler in the proper position for the desired speed. A neon pilot light glows when the motor switch is on, and serves as a reminder. Model B -12 is identical in construc- Turntable and arm platform are isolated tion except for the use of a 4 -pole in- from base plate with springs and rubber duction motor instead of the hysteresis dampers in Scott unit to eliminate vibration from outside sources. Motor and speed - model. - change assembly are also isolated from base plate. providing two stages of mechanical filtering. tached to each other, but are shock mounted from the base plate. The motor Rek -O -Kut B12 and B -12H look alike, and speed -change mechanism is also differ only in motor. Deluxe B -12H uses hysteresis motor. shock, mounted from the base plate, and the only connection between the motor is large enough to accommodate the pick- and the turntable is the drive through up arm mounting, except when transcrip- the soft rubber "universals." This con- tion types are used, and mounts in a struction is claimed to reduce motor rectangular opening 13 1/16 x 14 13/16 rumble to more than 60 db below rein. The drive mechanism consists of a cording level. stepped motor pulley which drives an Each speed has its own vernier adjust- idler, which in turn drives the inside of ment, by means of a knob on the panel, the turntable rim. The idler is carried on permitting a variation of ± 5% of the Rek -O lower- priced a bracket which is isolated from the turn- -Kut two -speed models nominal speed to match the pitch of an are available for 33 1. 3 and 78 or 33 I 3 musical instrument, table from by rubber shock mounts, and and 45, as desired. accompanying for the idler hearing is large enough to en- example. A built -in stroboscope permits Models L -34 and L -37 are somewhat adjustment if the speed to the exact smaller, and mount with a base plate Our city is an important which extends only in front of the turntable. L -34 has two speeds -33 1/3 and musical center ... and 45 -which are most useful for modern EONARD installations where no 78's are already AUDIO MART our people enjoy their in the collection. Model L -37 also has listening on the two speeds, with 78 being substituted for the 45. All models have a turntable cov- Not all of our customers know GARRARD RC80 ering of neoprene -bonded cork which what they want in hi -fi equip- Record Changer. eliminates slippage entirely. ment, but the one thing they Regardless of the other Hermon Hosmer Scott, Inc., 385 Putnam generally insist upon is the components they may Ave., Cambridge 39, Mass. (KS-23) The Scott 710 -A Stroboscopic Turn- GARRARD RC80 Record use, we find that our best table has several unique design features, Changer. We are constantly and differs appreciably from others. informed "musical" Briefly, it consists of a horizontally gratified by the people who take families build their mounted motor with a long stepped shaft, the time to tell us how satisfied each step being tapered slightly. Parallel audio systems around a to this shaft is a phenolic drum which is they are with their GARRARD GARRARD RC80 driven by one of three idlers, depending RC80 "World's Finest Record upon the speed desired. The drum is con- World's Finest Record nected to the turntable drive through two Changer ". Don't buy any Changer ". This is the soft rubber universals, and the drive consists of a hardened steel worm and a changer until you've tried this changer to buy at nylon gear located on the turntable shaft, one at and machined in place on the shaft. The turntable is driven by the shaft through a slip clutch which permits holding the turntable stationary for cueing, and EONARD which permits turning the table without damage to the worm. RADIO, INC. The turntable bearing is mounted on a Y- shaped casting which is attached to 69 Cortlandt St., New York 7, N.Y. the mounting plate by rubber- damped COrtlandt 7-0315 spring mounts, with extensions on the 1284 Market' Street San Francisco 2. Calil. casting carrying a mahogany platform "Complete hi -fi inventories at Underhill 3 -6000 for mounting any standard arm. Thus all times" The West's largest high Fidelity supplier. the turntable and arm are rigidly at-

44 AUDIO JUNE, 1955

www.americanradiohistory.com of construction, the motor is well away from the path of the pickup, and thus eliminates any induced hum from the drive motor. The design requires somewhat larger mounting space than most Listening turntables, but this would not be a disadvantage to many users. Turntable covering is a cork -latex compound to eliminate slippage. Quality Components Corp., Denville, N. J. (ICS-25) Several interesting features are incor- Scott Stroboscopic Turntable uses push but- porated in this design, which consists of tons to select speed, has vernier adjustment a 25 -lb. cast steel turntable mounted in is everything! for each of the three speeds. a nylon sleeve bearing and supported by a single ball thrust bearing and driven value. Speed ,election js made by de- by an endless cloth belt direct from the CHROMATIC HI -Q7 pressing any one of three buttons, which motor shaft. This reduces the rotating Today. all lookups. good. bad simultaneously starts the motor. The parts to just two -the motor and the or indifferent. have wide fre- fourth button stops the motor and disen- quency range, yet one will per- turntable -and isolates the motor from gages any idler. form smoothly, while the others the turntable by the long belt. The motor are harsh. shrill, etc. This construction permits mounting is mounted with double sets of shock The NEW high output the base plate solidly to any cabinet with- -Q7 has BALANCE, mountings to further reduce vibration. HI out the need for isolation, with all shock SMOOTHNESS, LIST- The entire base panel is supported by mounting built into the unit integrally. ENING QUALITY, steel springs which are damped with not equalled by any The base plate and pickup arm mounting felt. Another interesting device is the other pickup. . . board is 14% x 16% in., and requires a But-all the flow- expanding collet -type spindle which ac- depth of 4% in. below the mounting ery specifications curately centers the record on in the world can- board. the turntable and holds it from shifting or slip- not change the fact ping. that ONLY you can tell what sounds best to D. & R., Ltd.. 402 E. Gutierrez St., Santa you. Hear and compare the HI-Q7 with any Barbara, Calif. (KS-241 other pickup known and -you be the judge. RECORD CHANGERS Utilizing a new principle in turntable Plays all speeds. Equipped with Chromatic design, the DR -12 model locates the Collaro. Rockbar Corporation, 215 E. 37th DIAMOND and a sapphire stylus -both re- motor on isolation mountings outside of St., New York 16, N. Y. (KS-26) placeable AT HOME. the turntable area and drives with an The Collaro RC-54 record changer idler on the outer rim of the table. All retains most of the basic features that NEW COMPASS-PIVOTED parts are easily accessible and machined contributed in establishing the reputation ARM to professional tolerances. With this type of its predecessors, but embodies several Universally acknowledged as the most efficient improvements. This changer intermixes arm -barring none. No restraint No sizes records frontal oscillations No springs No all of -presuming that all fatigue Highest tracing efficiency. Equipped are of the same speed -and these may jor stylus -pressure adjustment. New adapter be stacked in any order of play without makes this superb AUDAX arm useable with any adjustment or presetting. The practically all cartridges. Reports from all of our branch- changing cycle requires only 6 seconds at all speeds. The steel turntable is es indicate that the Garrard weighted, and runs on a hardened spindle RC80 Record Changer meets with a ball -thrust race for smooth operation. The unit is constructed so that all of the qualifications for a when the changer is switched off by the fine high user, or at the -end of a stack of records, fidelity record changer the idler is disengaged from the motor ... regardless of budget. Be- cause of recognizable quality, unsurpassed craftsmanship, STYLUS -BALANCE and adherence to rigid engi- . . this redly works ... Canby neering standards...the chang- 75% of the cartridges in use, work with incorrect stylus- pressure. This means stylus and er that impresses every type record destruction. With the scales and gauges available hefetofore, it has been impossible of customer is the GARRARD to check stylus -pressure closer than 2 or 3 grams -one way or the other. That is 50% RC80 "World's Finest Record off- correct. This means deformation of groove. walls, which explains much of the echoes, Changer ". As low as $49.50 at ghosts and other distortion. Stroboscope -like, STYLUS -BALANCE accurately indicates cor- rectness or incorrectness of RC stylus-pressure. The Collaro -54 changer. Works with any arm and cartridge. Net $4.80 ... Add 25¢ if shipped from N. Y. shaft to prevent development of flat spots. Records are stacked on a center HIGH FIDELITY & COMMERCIAL spindle which remains stationary, and FREE copy of "ELECTRONIC SOUND STUDIO when the change cycle is initiated, the PHONO FACTS" at your dealers, record is slipped off the stepped spindle or write us. 701 Arch Street, Philadelphia, Pa. by an internal lever. As with all drop changers, the air cushion below the Branches in Allentown and Easton. record provides adequate delay in the AUDAK COMPANY 1042 Hamilton Street, Allentown, Pa. fall to avoid injury to the records. 500 Fifth Ave. Dept. A New York 36 916 Northampton, Easton. Pa .Stylus force is adjustable to as little Fine Audio- Efertronic apparatus over 30 years

AUDIO JUNE, 1955 45

www.americanradiohistory.com as 3 grams, and two heads are furnished the unit as shown in the following for installation of any desired pickup month's issue with the same model of cartridge. The mounting plate is 12 x changer as shown today would seem to 13% in., and the changer requires a indicate that there had been no changes. clearance above the mounting board of But this only serves to stress the fact 5% in. and 2% in. below. that the original design was fundamen- Two knobs serve as the controls -one tally excellent, and that any changes for speed selection, and one for turning made in the RC -80 over the years have the power on and off and for rejecting been minor improvements to perfect a record. During the changing cycle the the operation rather than to bring out a pickup is shorted so the user does not new model each year to attract the hear clicks and pops. A separate 4j-rpm customer's dollar in the manner of the spindle is available as an accessory to U.S. automobile industry. And while accommodate the smaller records, drop- the external appearance of the 1950 ping them in the usual way. After the model is practically identical with that last record side is played, the mechanism of the current RC-80, the changes that is shut off automatically.

Dual. United Audio Products, 202 -4 E. 19th St., New York 3, N. Y. (K5 -27) The Dual Automatic Record Player combines the features of a single -play turntable for 33 -1/3 and 78 -rpm records with the advantages of the changer for 45's. Sonie users have felt that there is no need for automatic operation with LP's and that they would therefore prefer the use of a single -play turntable for this speed, but when they want to play 45's the changer feature is practically a necessity. The Dual operates as a single -play The Garrard RC -80 has had no major turntable at both LP and 78 speeds, and changes in years, but minor refinements with the 45 spindle plugged into place have raised it to present high quality. c=) becomes a changer for this one speed. The starting and stopping at all speeds have been made are in the nature of refinements. The motor is now mounted Q on specially developed composition grommets which serve to eliminate rumble, and a tension lever releases the 3 intermediate wheel from contact with the turntable drum and the motor pulley when the unit switches off and also applies a brake to the turntable so that it stops quickly. Stylus force adjustment now has sufficient latitude to accomo- V date all types of pickup cartridges. Be- "Dual" Automatic record player is manu- cause of the rather extreme variation ally operated for LP and 78, changer in thickness of records, the pawl guide for 45's. has been modified so that the changer Q will handle both unusually thin or un- is automatic once the starting button is usually thick records equally well. A depressed, which selects the proper new spring mounting assembly now L stylus and inaugurates the starting cycle. makes it possible for the entire changer The arm moves to the center, determines to be snapped into holes in the mount- the record diameter and moves the arm ing board, and permits levelling from 3 to the proper position, then lowers the the top of the plate. stylus to the first groove. In the auto- The turntable spindle is ground and matic position -on 45's -the arm is lapped to a fine finish, and the bearings 0 moved out at the end of the side, another fitted into the spindle are burnished record is dropped, and the cycle is re- bronze. The ball race is located in a peated. When finished with the last side phenolic cage to obviate the metal -to- of a stack of 45's or when a side is fin- metal contact and to prevent creepage, ished at LP or 78 speeds, the arm is and the whole thrust assembly is sup -, lifted automatically, moved to the rest ported on a plastic washer instead of position and locked in place, and the metal -a more durable and rumble - motor is turned off. Normally furnished free arrangement. Rotor of the drive cartridge for this player is a crystal, motor is dynamically balanced to a but a magnetic cartridge will soon be high degree of accuracy -and this we available. The top plate is 13 x lOg in., have seen for ourself -and the spindle is and requires 3 in. below the mounting finished with an eccentricity of less hoard and 5I in. above. than .001 in., with the motor pulley held to an eccentricity of less than a quar- Garrard. British Industries Corporation, 164 ter of a thousandth. To further reduce Duane St., New York 13, N. Y. (KS -20) rumble and flutter, the rubber tire on The Garrard RC -80 was first adver- the idler is ground with a crown to tised in the pages of this magazine in eliminate small burrs on the edge which November, 1950, and a comparison of might detract from smooth operation.

46 AUDIO JUNE, 1955

www.americanradiohistory.com NEW STROBOSCOPIC TURNTABLE Makes Any Music System Sound Better Here's why recordings really do sound better The unique mechanical design lets you mount the when played on this amazing new turntable. turntable board rigidly to any cabinet. No extra mounting springs or vibration isolators are needed ; a scientifically I lie new "floating frame" suspension, developed by designed shock-mounting system for both turntable and H. H. Scott engineers, isolates both the turntable and pickup arm is already built in. pickup arm against all effects of sound, room, and motor vibrations. This system makes music reproduction en- No matter how perfect your music system may tirely free from the "muddiness" and distortion inherent sound to you now, the revolutionary design of the new 710 -A turntable will add startling new realism to music in conventional installations. reproduction. Stroboscope and Vernier Speed Controls Once you see and hear the 710 -A, you won't Here are more professional features of the II. H. ,e satisfied with less! Why wait any longer -now you Scott Model 710 -A turntable. A convenient built -in opti- :an enjoy music as it should sound. Ask your dealer cal stroboscope assures you of precision speed adjust- For a demonstration TODAY! ment even while the record is being played! TECHNICAL SPECIFICATIONS Three vernier -controlled speeds, each adjustable by Motor Rumble: more than 60 db below the recording level. ± 5%, let you change the pitch of the record to match an Wow and Flutter: less than 0.1% of rated speed. accompanying musical instrument. Speeds: push- button selection of 33-1/3, 45, and 78 rpm. Turntable: machined from a single heavy aluminum casting; aluminum coistruction eliminates magnetic pull on reluctance Gear Drive and Torsional Filters cartridges. A precision, helical -gear drive assures constant- Dissensions: including pickup -arm mounting board 167/e x 141/2 inches. speed operation. This drive was developed for H. H. Scott Power: 55 watts, 105 -125 volts, 60 cycles. Prices: 710 -A turntable -$102.00 net; West Coast price-$107.10 by Professor Earle Buckingham, of M.I.T., designer of 710 -XI mahogany base -514.95 net; West Coast price -$15.70 the drive mechanism for the Mt. Palomar 200 -inch telescope. Write for Bulletin A-655. Unique torsional and mechanical filters cut "rumble" and other extraneous disturbances far below the audible level. Styled in Mahogany and Stainless Steel The motor board is finished in beautiful, durable stainless steel. The contrasting hand -rubbed mahogany pickup -mounting board is furnished as an integral part of the turntable. H. H. SCOTT Inc. 385 PUTNAM AVENUE, CAMBRIDGE 39, MASSACHUSETTS

AUDIO JUNE, 1955 47

www.americanradiohistory.com Drive from motor to idler is direct arm down at the required 7 -in. diameter. from motor shaft on 78 rpm. and through A conventional 45 spindle is used for Hat rubber belts to intermediate drive the smaller discs, operating in the usual COMPARE' hafts for 45 and 33 1/3 to further iso- manner. A single -play spindle is also late the motor from the turntable at provided which disables the change this performance! these more critical speeds. Belts are mechanism when inserted in the turn- readily replaceable by the user. Except table opening in the normal position, FAIRCHILD during change cycle, the arm is free, and when inverted causes 10 -in. re- and may be moved from band to band cords to repeat continuously. `?O at will. For starting and stopping, the The "Pausamatic" control gives in- DIAMOND arm is actuated mechanically- consid- tervals ranging from 5 to 140 seconds at ered preferable to manual handling in 78 rpm. between 9 and 240 seconds at *37.50 CARTRIDGE average service. 45. and between 12 and 328 seconds on The RC -90 is essentially identical LP's. the lower figures being the mini- Fairchild's 220 Series cartridge guaran- with the RC-80. but has several ad- mum change time for the respective tees this distortion -free reproduction in ditional features -principal one being speeds. The arm has provision for ad- the entire audible range! vernier speed adjustment. which is of justment to accomodate any available Just look at these frequency response interest to the musician who is likely to cartridge weight. curves of the Fairchild 220 and two other play along with his records and wishes The Miracord chassis is 12% x 103/4 leading cartridges. See how Fairchild to set record speed accurately to match in., and requires 444 in. clearance above alone gives smooth, even reproduction pitch of reproduced music with that of the mounting board and 23 in. below. - completely uniform to 17,000 cycles his instrument. Plug -in heads will accept most car- with only slow roll -off beyond. This tridges, and a new adapter is now avail- means no unnatural harshness, no distorted Miracord. Audiogersh Corporation, 23 Park able which will accommodate the Audax sound! With Fairchild, you have only Place, New York 7, N. Y. (KS -281 models. the sound you were meant to hear! The Miracord XA -100 is a German import which offers a number of unique Radio Corporation of America, Front and Cooper Sts., Camden 2, N. J. (KS -29) FREQUENCY IN CYCLES PER SECOND features that are considered desirable by many. Among them are the push- The hi -fi components line of RCA in- button operation. incorporating a "start" cludes two record changers -the de luxe 11111. button which inaugurates the playing model SRC -51, and the lower priced 1I111E1 cycle : a "filter" button which reduces SRC -61 which is available as a "com- IME111111111111111=1111 scratch and high -frequency noise when ponent" chassis, or in an attractive base actuated : a "pause" button which in- as model 6JSH -1. 1111111I1BIIIMINI troduces a variable interval between The SRC -51 is well known, and pro- successive playings from a stack of rec- vides the user with reliable, trouble- FAIRCHILD 220 ords and a "repeat" button, which may 1111111INENI 11E111E11E be depressed at any time during the play- 11=1111E1111 IEIIEIE ing of a side and which causes the rec- 1111EEIE 11ER51 ord to be repeated at its finish rather ...iiil1EE= I/í111EE1E.N than continuing with the succeeding re- Í1111n IÍ11EEI cord on the stack. 1ni1/'mos 11m11aum The Miracord operates with a "Magic limn EEtM IMMURE Wand" spindle which is essentially a 1111111111E`_ 11111111\1111 thin version of the familiar 45 spindle. The records are stacked on the spindle, CARTRIDGE A CARTRIDGE B being held with three fingers equally spaced around the spindle. At the change cycle, the fingers are retracted to re- the RIGHT sound - lease the bottom record while three ex- always ! The deluxe model of RCA changers- FA LIA) 240 SRC -51. free service. The newer model, devel- Balanced-Bar oped by RCA, is more modern in appearance and employs a permanently PREAMPLIFIER mounted spindle for LP's and 78's, with Highest performance and operating sim- a slip -on 45 spindle being used for the plicity in this attractive Fairchild 240 smaller discs. When not in use it is Balanced Bar Preamplifier give you the stored in a well in the base. A standard world's finest sound equalization. type variable reluctance cartridge is provided with either model. Also, the Fairchild 240 features Listen- The 6JSH1- SRC-61 has a fingertip ing Level Control. Operating indepen- speed control which selects speed, turns dently of volume control, LLC provides "Magic- Wand" center drop mechanism, set on and off, and rejects records. The pleasant low -level listening and correctly push button operation, and "Pausamatic" arm is returned to its rest after the balanced normal listening levels all - control have proved attractive features of last record is played, and the motor is easily, without complex adjustments. XA -100 changer. Miracord turned off. It mixes 10- and 12 -inch same speed, and has a panting spring leaves hold the remain- records of the fingers simplified manual operation which al- ing records in place until the or skipping of their normal position. 10- and lows repeat playing return to portions of a record. 12 -in. records may be intermixed in any order. the larger ones actuating a back of the unit to direct Rex. Fenton Company, 15 Moore St., New lever at the 4, N. Y. (KS -30) the set -down position of the pickup arm. York Rex changer, manufactured in pmeh/LII/ EQUIPMENT " Positioning the speed selector to 45 The 9th AVE. & 154th ST.. WHITESTONE, NEW YORK rpm signals the mechanism to set the Western Germany, is currently' avail-

48 AUDIO JUNE, 1955

www.americanradiohistory.com able in four models -the Rex A with a over the permanently fixed small spindle. high -quality reversible crystal cartridge; and when not in use is stored in a well the Rex AM with two high- output four - on the base plate. pole magnetic single cartridges ; the Rex Model 1200 is a 4 -speed changer - A Special with a built -in preamplifier offering in addition to the usual three for the magnetic cartridge ; and the Rex speeds required by present -day phono- AA which is similar to the Rex A but graph records the fourth and talking has a plug-in shell to accommodate any book speed of 16 2/3 rpm. All V -M U.S. cartridge. Operation of the Rex models offer attractive styling, and are models is unusual in that the record is obtainable as chassis, or mounted in dropped about % inch at the start of various cabinets as complete phono- the cycling operation, pauses while the graphs. arm moves in to "measure" the dia- Webcor. Webster- Chicago Corporation, meter, then retracts slightly while the 5610 W. Bloomingdale Ave., Chicago record drops onto the turntable. The arm 39, III. IKS -331 then moves in to permit the stylus to V -M 935 -HF recarc changer features cast land on the record at the correct position. aluminum pickup arm, interchangeable The 141 series of Webcor changer, Thus the changer will work with any plug -in cartridge heats. differ in the cartridges with which they record size from 6 in. to 12 in. intermixed and in any order. The preamplifier in the Rex A Special incorporates three degrees of low -frequency turnover and three cutoff positions, and is thus suitable for replace- REVOLUTIONARY ment in a home system which does not have sufficient amplification or control to accomodate a magnetic pickup. NEW Au/ori,a#ìc Thorons Company, New Hyde Park, N. Y. (KS -31) The Swiss -made Thorens changer RECORD PLAYER differs considerably from most models now in use in that the motor drives the worm turntable shaft through a and The Only Automatic Record Ployer Chassis for gear, the speed being controlled by a Micro Groove and 78 RPM Records That Incorpo- rates Design Features Providing for Possible Future Changes in Record Sizes. Featuring Ex- clusive Automatic Tone Arm Locking Device Pre- venting Styli Damage When Not in Operation.

AMAZING! One Button Control for This Complete Exclusive Automatic 12-Step Operation Thorens model CD -43 has pause mechanism, is gear- driven from governor -con- V trolled motor. Complete with 1- Correct Stylus Is Selected automatic 2 -Tone Arm Unlocks tlyball governor, and the motor is 45 RPM 3 -Motor Starts mounted with the shaft parallel to the spindle, 4 -Arm Lifts Up and Moves turntable. The speed- change mechanism shock mounts, Toward Center employs a series of planetary gears. line cord and 5 -Arm Sets Down on Rub- output cable. The model CD -43 changer intermixes ber Roller 6 Across Rec- 12, 10, and 7 -inch discs, and is fitted -Arm Sweeps with ord stop, start, pause, and reject con- 7 -Finds Record Edge of Any trols on the panel. It is easily adjustable The DUAL 2uß chassis is a marvel of engineering perfection ... produced by craftsmen who for generations Size Record for stylus force, and comes with shock have ballt precision equipment world famous for superb 8- Roller Retracts (Like mounts; a switch permits semi- manual accuracy. Here is a record player that protects your Landing Gear of Planer records as It plays them ... Is an AUTOMATIC PLAYER Stylus Sets Down on operation. when it should he, and an AUTOMATIC RECORD 9- CHANGER when the need arises. Incorporates shielded Starting Groove of Record V -M Corporation, 280 Park St., Benton motor of special design, adaptable to 110/125, 150/100. 0 -Arm Lifts Up and Moves and 220/240 volts, 60 cycles, A.C. The constant speed Harbor, Michigan. 1 KS Back to Rest Position, -32) switching and changing cycle of DUAL 280 is com- the When Run -Off Is Model pletely independent of the rim driven turntable. Auto- Groove 935HF is the current model matic drive disengages when the turntable stops. Reached at End of Record intended The for the "hi -fi" market. This balanced turntable is equipped with a non -slip rubber 1 -Arm Sets Down; Locks model is a mat. ADVANCED DESIGN CARTRIDGE REPRODUCES center -drop design, using ALL FREQUENCIES FROM 25- 20,000 CPS, AND HAS Firmly a guide arm to steady the record stack. REPLACEABLE STYLI. The plexigum tone arm is 2-Motor Shuts Off The arm is cast aluminum, and is equip- completely free from resonance. Built -in, 3- position noise filter. Size: 13" z 10%"; minimum depth- 3" ; minimum ped to accept plug -in cartridge holders, height -5% "; shipping weight 52 lbs. DIOPROt, and most cartridges may be fitted to the Write for Specifications and Name of Nearest Distributor holders with little effort. The laminated turntable is weighted UNITED AUDIO PRODUCTS /lea and balanced to assure smooth operation, I and a four-pole motor minimizes ex- Div. of United Optical Mtg. Corp. ':\,_ irF/!s"" ternal hum fields. The 45 spindle slips 202 East 19th St., N. Y. 3, N. Y.

AUDIO JUNE, 1955 49

www.americanradiohistory.com are equipped; 141 employs a ceramic National Company, 61 Sherman St., cartridge, while 141 -270 employs a GE Malden 48, Mass. (KS-34 I variable reluctance unit with sapphire The National line of hi -fi equipment styli. Both models will play intermixed which was introduced about a year ago with a tuner, a preamplifier, and two power amplifiers, has recently been expanded to include a number of loudspeaker enclosures and a record changer. The Horizon 100 changer was designed for use in hi -fi systems, and is reliable, smooth in operation, and is said to be jam -proof and stall -proof. It intermixes 7 -, 10 -, and 12 -inch records, provided all are of the same speed. and they can

Stromberg Carlson PR -450M changer is a Garrard RC -80.

Bred line. Under the PR -450M number. the newest model of GE triple -play reluctance cartridge is supplied, using sap- ; a Newest Webcor intermix changer, model phire styli Model PR -455M utilizes 141. diamond for the microgroove stylus.

tacks of 7. 10, and 12 -inch records, and RECORD PLAYERS turntable speeds are held to narrow David Bogen Co., Inc., 29 Ninth Ave., limits, even when the turntable is loaded. New York 14, N. Y. I KS -371 The speed control knob has a neutral The Lenco turntable imported from position to remove the idler wheel from Switzerland and sold in the U. S. under contact with motor shaft when the the Bogen name is of somewhat differ- changer is not in use. An adapter is ent design than most players. The motor available for playing a 1 -inch stack of is mounted with its shaft horizontal, but 45's without the use of individual re- The "Horizon 100" changer fills out the shaft is a cone that actuates an idler cord inserts. All records and sizes may National's high -fidelity line. which, in turn, bears on the bottom of the turntable. The position of the idler be played manually. last rec- After the be stacked in any order of play without is controlled by the speed selector lever, ord is played, the arm is returned to any adjustment or presetting. The com- and a continuous variation is obtain- the rest and the motor is shut off. plete change cycle requires 6 seconds. regardless of turntable speed setting. The unit employs a 4 -pole motor for minimum hum field, has automatic dis- Our customers spend a lover engagement of the large idler wheel, When a music lot of money on comes into our studio switches off at the completion of the last record in the stack, and is equipped with records. They want to and wants a hi -fi system two plug -in heads which will accomo- enjoy them properly, worth listening to, and date any cartridge. The Horizon 100 in- protect them at cludes a GE cartridge, all cables and and without unnecessary, connectors, and the mounting base, the same time. They costly gadgets, we which may be either blonde or mahog- tell us that because always recommend the any. of pusher platform, GARRARD RC80. Sightmaster Corp., 111 Cedar St., New one piece removable For quiet performance, Rochelle, N. Y. I K$ -351 center spindle, and ease of operation, and The Sightmaster Corp. markets a correct tracking and group of high fidelity units under its own years of dependability name to make it possible for the music tangency, the one ... we know we can tell lover to assemble a complete system changer that gives our customers with with a minimum of cost in comparison them what they need to the results obtained. Among the line is GARRARD RC80 confidence to buy the is a record changer imported from Eng- the GARRARI) RC80 land which incorporates most of the "World's Finest Record desirable features in such a unit. It in- Changer ". Our salesmen "W'orld's Finest Record termixes 10- and 12 -inch records, shuts Changer': Come in and off when last record is finished, mutes will gladly it at hrar it :tt the pickup output during the change demonstrate cycle, and utilizes a reluctance cartridge with a diamond stylus for LP records. ca.rli.rkeu,tly $c:uc 1944 1221 Clifford Stromberg Carlson Company, HOLLYWOOD ELECTRONICS St., Rochester, N. Y. t KS -36 i Terminal III DISTYISUTORS OF HI-FI COMPONENTS ACA,',/0 (GPI' Like many another manufacturer, - Stromberg- Carlson does not build its own record changer, but has chosen the One of the nation's Garrard to offer under its own type Hi -Fi Components Exclusively leading sound studios - number, Model PR -450M. All descrip- since 1944 open 'till 6:15 P.M. daily tive material for the Garrard RC -80 ap- 7460 Melrose Avenue, 85 Cortlandt Street, N. 1 plies to the unit available as one of the Los Angeles, Calif. \\ Orth 4 -3311 E.. components of the Custom Four Hun- WEbster 3 -8208

50 AUDIO JUNE, 1955

www.americanradiohistory.com SONOTONE It gives you all QUICK FACTS the music-and none ON of the problems! CRAM/CS NEW SONOTONE 1P CERAMIC CARTRIDGE

By ROBERT L. LEWIS CUTAWAY VIEW 1. CONVENIENT SIZE If you haven't heard too much about cer- (Actual size 1" long) AND DESIGN amic cartridges, it's because this type is relatively new. Sonotone discovered the principle in 1946. Inherently, it had major advantages over other cartridge types -no 2. CLIMATE -PROOF deterioration from humidity or tempera- CERAMIC ELEMENT ture... no magnetic hum pickup, no need for equalization, plus far higher voltage output. Since then, we've constantly improved the response curve, to its present superlative "flat" range. The 1P described here is brand new. It's a single -needle type. We also make a turnover, two -needle type that operates on the same principles. Incidentally, both types eliminate one nuisance -you can remove or replace the needle in a second, just SINGLE, JEWEL -TIP with your fingers. Simply snap it in. NEEDLE

4. HIGH -COMPLIANCE MOUNTING

5. SNAP -FIT NEEDLE REPLACEMENT

1. Easy to install. Fits most arms now in use. 3. Replaceable needle, diamond or sapphire. Models for 33 -45 rpm, or 78 rpm. 2. Ceramic element gives superlative response compliance and low -mass (see curve)- requires no preamplification or 4. Extreme lateral low wear. equalization! No deterioration problem as design give superior tracking, with other types... virtually immune to hum 5. Needles snap in, snap out easily without This diagram helps explain why, using pickup! tools. Sonotone ceramics, you get a flat response without an equalizer. With a velocity type New, Simpler Way to Finest, Noise -Free Reproduction pickup, the voltage output will be 30 times 1 P Cartridge gives you superb response- compare it as great at 10,000 cycles as at 50 cycles. It A Sonotone Ceramic responds to side -to -side speed of needle with any type of cartridge at any price! Ih addition, this Sonotone Ceramic movement. But our ceramics work on the Cartridge eliminates expensive, cumbersome equipment...along with all the "amplitude" principle-they respond to the noise inherent in such circuitry. You get full-range, quieter reproduction - amount of side -to -side movement. more simply, and at lower cost. Model 1P with sapphire, $8.50; with diamond, So a Sonotone ceramic cartridge will $30 list. play back RIAA, Orthophonic, AES, LP RESPONSE 30-15,000 ± 3 DM and other common curves so close to "flat" that your ordinary tone controls +5 111111 11Illi 1111111111111 11111111111111M 5. amply cover any needed delicate adjustment for individual records...and indi- 0 CO vidual ears. About hum - you'll be glad to know that 5 IHII 5 Sonotone ceramics give a high voltage out- HAM 11111111111111111111111111111111 put that overrides hum, and require no boost 30 50 100 300 500 !KC 3KG 5KC I0KC *KC at hum frequencies. And the nonmagnetic Response to new industrywide RIAA characteristic shows how 1P self-equal- structure means no worry about nearby fields or turntable causes. izes, because it works on "amplitude" rather than "velocity" principle. Sincerely,

CORPORATION SONOTONE ELMSFORD, N.Y. Head of Electronic Applications Division Write Dept. CA-65 for free Specification Sheet

AUDIO JUNE. 1955 51

www.americanradiohistory.com able, although there are notches in the idler is caused to engage the turntable lever quadrant to indicate the three basic rim and the proper step on the shaft by speeds. The over -all range of speeds is a speed control knob, being lifted out of engagement between steps. The pickup arm actuates the starting switch when moved to the right, and at the end of thu record the motor is switched off automatically. Plug -in -heads and stylus force adjustment permit the use of any desired pickup. The unit has a minimum of rumble, and flutter and wow are undetectable by the ear.

RECORD EQUALIZERS Relatively few of these are on the market today because most modern amplifiers are equipped with adequate facilities to acommodate all the recording characteristics in use, and most of those Pickering Compensator provides correct that have been used in the past. Some equalization for six common character- David Bogen model B50 -4 record player manufacturers provide simple preampli- istics. utilizes idler which drives underside of fiers turntable. which are designed with a turnover frequency close to 500 cps, and these a preamplifier which has a 500 -cps turn- can be employed with passive variable over. The compensator changes the re- from 29 to 86 rpm. The turntable is equalizers to match the many character- sponse to match six different curves: weighted pounds balanced. -3% -and istics. Among these products are the European 78, London 33 and Old LP, It is covered with a ribbed rubber pad. following : Old Capitol and Old AES, New AES, The pickup arm is die cast, and em- (Ortho, RIAA), flat highs and a bass ploys ball suspension bearing for mini- General Electric Co., Electronics Park, Syra- response that is not rolled off, and a mum is friction, and stylus force ad- cuse, N. Y. normal bass position combined with a justable from 6 to 12 grams. Operation The GE Record Filter, Model Al -901, cutoff beginning at 3000 cps for noisy of the motor begins with a slight move- records. For the user who wishes to ment of the arm away from the turn- offers fourteen separate frequency adjustments to cover the full audio fre- combine a simple unequalized power table, and when the record is played, the amplifier with a preamplifier with fixed velocity trip shuts off the motor. In the quency range. The low- frequency cutoff filter has four positions -one is flat, low -frequency boost, this unit gives con- off position, the idler is disengaged from siderable flexibility, and eliminates the contact with both the motor shaft and and the other three cut off at frequencies of 40, 60, and 80 cps respectively, to eli- need for a "control unit" unless tone the underside of the turntable to prevent controls are imperative. forming flats on its rubber rim. Two models are available -the Stand- ard, which has a wide -range piezo- ACCESSORIES electric cartridge with two sapphires, Audak Company, 500 Fifth Ave., New and the De luxe, which is supplied with York 36, N. Y. (KS -2) a GE RPX -050 cartridge. It is also available without cartridge in Model The Audax Stylus Balance employs B50 -4LC. The player requires a mount- a simple beam balance arrangement with ing space of 15 in. from left to right and knife -edged bearings, and two fixed I l h in. from front to rear, with 23 in. weights -6 and 2/ grams. A groove in clearance above the mounting board and one arm accomodates the stylus, and a small stud on the other end serves to 1 h below. It is furnished with plug -in plastic head and shock mounting springs. locate the weights. The 244-gram weight will fit over the top of the 6 -gram weight G.E. Record Filter provides control flexi- Garrard. British Industries Corporation, 164 bility when used with fixed preamplifier. Duane St., New York 13, N. Y. (KS -20) minate rumble and excessive low -fre- The Garrard Model T record player quency response when desired. The is a manual unit which incorporates an second control provides six compensator automatic start and stop mechanism, but settings to match the system response to which is built to Garrard standards the six principal recording curves used throughout, in spite of its low cost. To by the industry. The third control pro- start the motor, the pickup arm is lifted vides for flat and three high -fr suency from its rest and moved slightly to the cutoff positions -9000 cps, 5111 cps, right to actuate the switch. When a re- and 3000 cps. This permits the elimin- cord is finished, the motor is stopped by ation of scratch and high -frequency dis- action of the trip mechanism. tortion on older records. The entire unit For applications where a simple is housed in a neat phenolic cabinet, and Audax Stylus -Balance is one of simplest player is required, this one offers high - is connected between a GE pickup and means of setting stylus force to desired quality performance and ease of oper- a preamplifier with fixed low- frequency value. ation in a small and compact unit. boost. The compensator uses no tubes and therefore does not require any power to indicate 8% grams, when desired, al- Miraphon. Audiogersh Corporation, 23 supply. though the 6 -gram value is recommened Park Place, New York 7, N. Y. (KS-28) by Audak for LP reproduction. The The Miraphon XM -110 is a very sim- balance arm is made of soft aluminum to ple mechanism for playing records, but Pickering Er Co. Inc., 309 Woods Ave., avoid damaging the stylus, and for ex- much of its virtue lies in its simplicity. Oceanside, L. I., N. Y. (KS-9) perimental purposes additional weights It consists of a four -pole motor mounted The Pickering 132E record compen- of 6 and 1% grams, respectively, are on rubber grommets to the base plate sator is designed to work between a available to give a range from 1% to 16 and equipped with a stepped shaft. An high -impedance magnetic cartridge and grams.

52 AUDIO JUNE, 1955

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www.americanradiohistory.com To use the Balance, the stylus is keeping. This is an excellent unit for placed in the groove and the 6 -gran the critical fan who wishes to be able to weight is placed on the other end of measure the stylus force easily and ac- the beam. The balance is held at a near curately with a minimum of effort. horizontal position with the fingers, then released and the movement -if any-of Garrard. British Industries Corp., 164 the balance beam is noted. This unit is Duane St., New York 13, N. Y. not intended to measure the value of 11(5-20) stylus force, but only to permit setting The Garrard stylus pressure gauge the force to the correct value with ease. operates on a unique principle. The stylus is placed on a small platform at one Pickering & Co. Inc., 309 Woods Ave., end, and a lever is actuated by the fin- Oceanside, L. I., N. Y. (KS-9) gers at the other to bring a zero pointer in line with a mark on the face of the The Pickering balance is so simple gauge. The position of the hand -actuated that it is usually presented as a souve lever indicates the stylus force. This ar- nir of the audio shows. It consists of a rangement simplifies the reading of the in. flat aluminum strip about 1/32 thick scale, which is calibrated to a maximum with a in one end for the depression of 15 grams. stylus, and an indication on the other for the correct placement of a penny - Scheer stylus -force gauge gives accurate Livingston Electronics, Livingston, N. J. which may he cemented in place if de- (KS -391 sired. Markings on the strip indicate the dial indication between 2 and 15 grams. fulcrum when the stylus force is The Livingston gauge has been on at the scale directly. This unit is calibrated in value marked. For a fulcrum a thin rod the market for some years and is un- grams from 2 to 15 on either side, and is may be used a finishing doubtedly one of the simplest models -even nail would equipped with a limit pointer which is serve-and the strip is rolled along the vet introduced. It consists of a molded pushed to the maximum excursion of plastic case which holds a spring wire "fulcrum" until the penny and the pickup indicator hand serves retain arm balance. read the and to in place. The stylus is put on a small The pressure is then the indication. The limit pointer is reset from the position of the fulcrum. platform and the deflection of the wire at will by means of a knob through the indicates the pressure in grams on a cover glass. Retaining rings for the calibration molded in the case. The con- George Scharr Co. Inc., 200 Lafayette St., cover glass have small pointers which and New York 12, N. Y. (KS-38) struction provides for adjustment, can be set to show where the stylus the accuracy is quite good. When not in The Scherr gauge is built like a ma- force should fall in case of rapid pro- use the movable element is covered by a chinist's indicator. The arm is placed duction measurements. Other models are portion of the case. under the pickup head while the instru- available with different ranges, and with ment is held with the dial in a vertical or without the limit pointer. Each gauge Ingalls Electronics Co., 30 West Putnam plane, and the stylus force is read off the comes in a padded wooden box for safe- Ave., Greenwich, Conn. (KS -401 The Acousti -Pad is made of a micro - porous rubber material (trademarked `Feltan' by the American Felt Company) and is an old established product re-

1 sembling felted rubber. It is intended as an isolation between metal turntables i#0, and the record, and is a desirable accessory to use with flocked turntables

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P I That Weathers, the most advanced .phonograph pickup system, I/ features: / 1 gram tracking force e j/ 4 - 40,000 cycles frequency response without ringing / resonance Virtually no record or stylus wear le 1 Natural sound reproduction 1/ I/ Ingalls micro -porous rubber is felt loaded Complete stability for damping, makes good isolation for changers and turntables. I, Distortion lowest ever recorded l/ No leveling of turntable required They are available in 8 -, 10 -, and 12- inch diameters to fit most turntables. A 17 -inch model is available for use on professional turntables. Ask to see and hear its startling / Latex impregnated felt is a felt strip features at your nearest quali- / cut with an "arch support" for mounting fcd dealer. / turntables and changers in cabinets 4 where there is appreciable vibration. Since it is well known that neither felt 1/ / nor rubber alone will serve to eliminate Weathers Industries, Inc. low frequencies, it is probable that the u / presence of the felt fibres in the porous :/ 66 E. Gloucester Pike `e rubber mixture serve as a resistance and l Barrington, N. J. / prevent setting up any resonant frequencies in the material, as could be done with rubber alone.

54 AUDIO JUNE, 1955

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BRAHMS clwru., am:neur :Lilt! I rofe..ional l in an grade - these values counterbalanced by some typically YOUNG school on up) has so seldom been recorded and French playing of German music that does the Brahms: Serenade in A, Opus 16. then with such so -so results. This performance intensely German Schumann no great good. #2 The "Rhenish" never showed its orchestral Amsterdam Concertgebouw, Zecchi. soars far ahead of the two others now available, the ponderous, muddy (if expressive) Viennese textures with such clarity as here. But the Epic LC 3116. version under von Karajan (Col. SL -157) and sound. for Schumann, is most peculiar if you One of these days we are suddenly going to dis- the chrome -plated smoothness of the Robert Shaw know the "Rhenish" well in other version.. The cover that some of the finest music Brahms com. version (RCA LM 6004) of some time back. French orchestra, in this day of standardization, posed came before he grew that formidable beard, The "Requiem" came at the end of Brahms' remains astonishingly unlike all others. You can before he so much as wrote a Symphony Number long youthful period and it marks a turning hear in this one the peculiar Matting of the One. To be sure, both of these events, marking point, towards the greater concentration-and French brass, the heavy vibrato of the "French" Brahms' official entry into the ranks of "mature" tougher discipline -of the late years. It's a big horns-unthinkable in German music-and of the composers, came well along in his life, in full work, in size and in expression too, but it trumpets, the nasal sound of the oboes, the odd t middle age. Brahms had a long youth. But the is still full to bursting with that all -out, un- out -of -tune quality to the ensemble, all elements very quality in his character that made him apply restricted and juicy Romantic expression that quite foreign to Schumann. And though such rigorous self -criticism to his own work that Brahms grew increasingly away from in his Schuricht himself has an echt German back- he could not launch his First Symphony until later years, as though it were beneath his ground, it's interestingly clear that even he can- his forties, also -we now can realize -acted as dignity as a "great" composer. The "Requiem" not make French musicians play German music a drag and a limit on free expression, in the simply oozes romance. It's free and unconcen- like Germans! A thousand small details add up interests of supposedly "higher" artistic con- trated, according to his later standards; yet al. to a strong sense that these players are recast reinterpre- e centration. ready the lines have tightened, the "higher ing Schumann in a French mold. You'll follow me easily enough when you try organization" is there, the wheels within wheels ting all his pet little effects into subtly different this record of the Second Serenade. It's a dilly are operating smoothly and marvelously. But the patterns of their own strong- minded devising. and a lulu. The point I'm after is simple. The spontaneity is not yet affected. Interesting and alive, as I say, but not Schumann two early Serenades, opus II and opus 16, rank This is why the piece is so extraordinarily by a long sight. officially well down in the heirarchical scale of The Overture, Scherzo and Finale is an early musical greatness. They are "little" works, semi -symphony, in purpose not unlike the Brahms youthful. informal, unpretentious. They rank Serenade above (indeed it was called a serenade) ; among the Second Looeys and the Ensigns along- KEY this too, was one of the preparatory works lead- side the Big Brass of the four Brahms Sym- ing to symphonic writing and this too, is a Outstanding recording for the type phonies, the piano concertos and the like. You free and easy expression, turned out without of music. these heart searching after greatness on the composer's won't find Brahms judged very often by a Big bass sound. pieces and for that matter you won't find them part. Always a good idea! To be sure it is some- Close -to, sharp- edged, in big live- on many symphony programs either. They aren't what repetitive, less well organized and with a rather listen to ness. lesser profusion of ideas than the symphonies; "important" enough. But I'd Closeto, in deadish acoustics. this record now than to all the symphonies but it is even so a strong and youthful piece with right re over-all miking in big Distant, catchy and memorable ideas, a highly worth- and concertos, to choice, because there is a liveness. kind of music here that can't be matched any- while item to get to know. 14 Good try for hi -fi demonstration. where else in Brahms -Big Brass or no. t Big, golden liveness. Brahms is a rather special case. He was born o Close -up piano sound, small -room r Schumann: Piano Quintet in E Flat; with a marvelous gift of musical spontaneity, effect. la) in E Flat. Bohle, bet he developed a rigidly critical Piano Quartet Walter conscience that rr Recorded level rather low. was dead set against that spontaneity for the pf., the Barchet Quartet. e Solo (s) close -to and loud. rest of his life. He tried hard -too hard. In Vox PL 8960 MIS Solo close -up, accompaniment in plenty of ways he achieved "greatness" and his background. Schumann: Piano Quartet in E Flat. big works show it plainly enough. Yet in- S 'Brahms: Horn Trio in E Flat, Opus 40, Solo quite distant -sounding and/or creasingly, as we get away from him, they "smell low -level. Horszowski, Schneider et al 1 N. Y. Quar- of the lamp." They are, one might say, success- Some distortion audible. fully forced. tet). Enough said. The serenades fall into the Columbia ML 4892. class of works where -thank Heaven -- Brahms Overlapping recordings here of the Schumann for one reason or another felt no need to be popular among singing groups. It "sings it Piano Quartet in these two discs of three pieces "great " - -and wrote for sheer pleasure! The self," it's a natural for anybody with half a in the same key. The bigger name artists are Liebeslieder waltzes are in the same category. chorus voice; and its sincerity is so honest, so upon the Columbia disc, but on direct com- "Little" works of no great consequence -and wonderfully straightforward, that a high school parison I think I like the Vox recordings better, hence old Brahms turned off his conscience and student can revel in it as well as-or better partly on performance, partly in the recording. really let loose, as the musician that he was. than -any professional. This performance catches The familiar and much -beloved Schumann Try it and see. The Second Serenade is quite that sincerity and the drive and excitement of the Quintet (string quartet plus piano) needs a big, stunningly and lyrically played, to perfection, by work as no recorded performance has before. masculine, vigorous playing, with real early. this Dutch orchestra under an Italian conductor. Lovely recording, utterly natural and well Romantic gusto; paradoxically, Myra Hess has An unlikely combination (and the Schumann balanced. always been a prime exponent of the piece as one "Rhenish" Symphony in an earlier release was P.S. The two soloists are both superb. of the strongest of our great lady pianists. spoiled by it) but here it works. Big, live, dis- (Remember, Schumann's wife Clara was a tant mike pickup, warmly hi -fi. ROMANCE great pianist and performed most of his works.) The playing here is just right, for my ear, with- * Brahms: A German Requiem, Opus 45. Schumann: Symphony #3 ("Rhenish ") ; out a trace of the tired sound we often hear Frankfurt Opera & Museum Orchs., Opera Overture, Scherzo and Finale Opus 52. in over -played works like this one, and the Vox Chorus, Solti. Lore Wissman, sop., Theo Paris Conservatory Orch., Schuricht. recording,` "bi -fi" in style, a big sound with Adam, bar. LL plenty of liveness and a closeup clarity of detail, London 1037. very well suited to the mood of the Capitol PBR 8300 (2) is piece A gorgeous recorded sound and a lively pair itself. Here, at lait. is a really good recording of of performances are enough to recommend both The Piano Quartet is a work in a similar the Requiem. It's strange that this work, the sides of this disc and the second piece is a vein but less successful -yet well worth hearing. long -time enthusiastic favorite of a thousand seldom -heard "find" of a most interesting sort- The Vox performance is again a robust and

AUDIO JUNE, 1955 57

www.americanradiohistory.com alive one, excellent for the music. Recording has player as well- somewhat surprisingly in view of Still another souvenir (wherever or whoever the piano closer here, and there is some key - all the fuss about him! This playing of the Hapsal might be), and along with it a goodly action rattle to be heard, as well as a good deal Franck is warm and lovely and unassuming; collection of a concert rarity -piano music by of close -to scratching from the strings. (Also, I Yampolsky's piano (they often play as a team) Tchaikowsky. Pianists seem to avoid Tchaikow- think, a trace of distortion.) Not important de- is similar, and my only reservation is that the sky, as orchestras rush for his corresponding tractions. piano, though beautifully recorded, is too much works for orchestra, and the only reason would The Columbia version of the same work is in the background, the violin relatively too appear to he that T's piano technique isn't quite distinctly more subdued and I find it less effec- prominent. Not a good balance. as virtuoso -style, at least in piano solo, as his tive. Part of the difference is in a less robust re- Though Szymanowski was a Pole from the orchestral writing. cording; Columbia's is technically a better Ukraine, his music, in the fairly early work Reisenberg is one of those big, hefty, mas- balance. but this particular kind of music is, (1904), is not far removed from Franck him- culinely muscled lady pianists (I am speaking as I say, well suited to Vox's big, fat "hi -fi" self -very late- Romantic, chròmatic (half- steps), strictly musically -I haven't set eyes on the sound. (In my copy, Columbia's surfaces are less a kind of feminine Rachmaninoff with French lady) of whom we have a number in this country. silent than Vox's Columbia- pressed surfaces.) overtones. I'll take the Franck any day, Ray Lev is another, and the style of playing Part of the difference is due also to a less -than- commands big audiences. It is not exactly wholehearted Romanticism in the strings, par- n subtle here, nor always musical, but the good Franck: Quintet in F Minor. Curtis String ticularly the violin (Alexander Schneider) and natured energy that is Quartet; Vladimir pf. Reisenberg displays un- cello (Frank Miller), who have expressive duets Sokoloff, doubtedly attractive and the piano adds up to not well realized here. Westminster WL 5331 rousing Tchaikowsky, longwinded but in many On the reverse of the Columbia disc, the This recording is a puzzler- -I've been through spots very listenable. Fine piano sound of the Horn Trio, another of those later youthful it twice from beginning to end, trying to figure close up, intimate sort in dead acoustics. Brahms works, is similarly disappointing, ex- it out. The Franck Quintet, an early and very cept in the peppy last movement where things intense work of his, somehow lacks the sincerity really begin 'IT Wagner: Tristan: Prelude and to move. This is a wonderfully en- and the impact that I've always felt in it in the Liebestod; dearing work, close to the "Requiem" in its past; my best explanation is two -fold. First, the Die Götterdämmerung: Dawn, Siegfried's spirit, in its youthful exuberance already tem- Curtis group is a highly professional one which, Rhine journey, Funeral Music. Paris Con- pered. but not hampered, by a maturing sense of however, plays Romantic music, especially this servatory Orch., Schuricht. concentration and musical architecture. It can be all -out sort, with cool precision. Too cool. (The warmly and London LL 1074. directly played; here it seems fussy, pianist is more outspoken.) Secondly, this labored, sententious, too slow. An Here's that academic kind domestic Westminster is recorded in a wholly dangerous French. German combin- of performance, professional in a not so good dead studio acoustic, the strings very close, the :.tion again, as in the Schumann disc above, and sense. results are again piano somewhat muffled. Technically it is a decidedly mixed. The "Tristan" superb job, but acoustically it suspends Franck's side, the usual Overture and Love Death, comes off very well; there is something that e Schumann: Quartets in F, Op. 41, #2; warm, sensuous music in a sort of acoustic appeals to the in A, Op. 41, #3. New Music String Quar- vacuum that is most disconcerting. An interesting French musical mind in "Tristan" convoluted tet. contrast with Westminster's European chamber chromaticism (not so far removed from Franck) and it often Columbia ML 4982. recordings, among the most live and warm leads to quite inspired French acoustically. performances. Mendelssohn: Quartets #2 in A mi., Op. But " Götterdämmerung" is something else again. In spite of Schuricht's best efforts, this 13; #5 in E Flat, Op. 44, #3. New nil Bizet: Symphony #1 in C; Patrie Music String Quartet. playing is just abysmally and willfully out of (Overture), Orch. de la Suisse Rom., spirit. Indeed it's amazing how single -mindedly Columbia ML 4921. Ansermet. the French musicians commit honest sabotage Most string quartets lack pretty names, as London LL 1186 upon Wagner's even- musical whim and mysti- witness the garble cism. A strong- minded by good of numbers above; but their Almost everybody knows the delightful Bizet performance content is not affected. These are a relatively French musicians and therefore it is all the symphony, only rediscovered a few years ago; rare breed, the high- Romantic, which means more belligerently and flagrantly unWagnerian. that this is a wonderfully recorded and very pleasing they are poetic, soulful, lyric, emotional, Again, beautifully recorded with utmost inner moody, version of it, as hi in the fi as in appropriate for and what -not. Not all quartets clarity, including those same unwonted and out - are dry and such an unassuming piece. "Patrie" is another "intellectual!" (Some of them are - or get played of -place French sounds, the snarling oboes, the matter. It's a rousing, piece of political occasion - that way, anyhow.) unthinkable wavering French horns. recommend music, musically quite preposterous, but in. I The Schumann quartets are superbly the disc to many who will find it a most in- played cidentally (perhaps not quite so incidentally here and are thus most enjoyable just teresting study in national temperament as ap- for about .) a super-hi-fi wonder with enough noise any ear. The New plied to music. Music Quartet has captured to blow dozens of hi -fi fuses. Impeccably re- the sensitive,nsitive, poetic, breathless feeling of the corded, too. music as it is very seldom conveyed. Good Schumann is a rare thing nowadays and this dt Dvorak: Piano Concerto in G Minor. is exceptional. Charpentier: Impressions d'Italie. Aubert: Firkusny: Cleveland Orch., Szell. The Mendelssohn works are not as persuasive La Habanera. Nat. Opera Orch., Fourestier. Columbia ML 4967. in themselves, though technically they are no Angel 35120. Dvorak's symphonies are somehow more cogent, doubt Netter put together. As usual with this I looked forward to sampling this -there are less diffuse than his concerti, which tend to composer, the earlier one, #2, (actually his many very pleasing things in the minor French ramble on and on, lyrically. This one is a special first) is the most attractive; it was tossed off at music of the mid 19th century that are now case; the original piano part, which it is claimed age 18. Mendelssohn's habitual "talkiness " emerging. But I was disappointed; the Charpen- - was badly written so that the orchestra over- vast quantities of little notes, fussy rapid figures tier ("Louise") is hardly more than salon stuff. shadowed it, has been re- written most zealously that go on and on, make the quartets difficult to The Aubert is a short extra at the end that by a Professor Kurtz, who happens to been project. (The same fussy notes in his orchestral didn't hit me as any special saving grace. have Firkusny's teacher. Firkusny has a semi -monoply writing are distributed here and there for plenty on the revision, by dint of much hard of instrumental color and variety.) But, again, playing rid Tchaikowsky: Souvenir de Florence, Op. over the years. this New Music group does a marvelous job 70, arr. Winograd. Arthur Winograd String Perhaps the piano was overshadowed; my first at putting the fussiness of detail into its place, Orch. impression is, however, that the Professor jumped bringing out the larger romantic sweep of M -C E3173 musically from the frying pan into the fire. The emotions. These two discs make a first -rate in- -M revised piano part is brilliant and troduction to the 19th century quartet. Ex- effective but This is an interesting item: it was originally it reeks to my ear of the kind of piano pedagogy tremely well recorded. six written for strings: violins, violi and celii that thrives on Rachmaninoff and the like. I'd in pairs (a string sextet) hut its sound was suggest that Dvorak has perforce traded some of Franck: Symphony in D Phila. evidently not too satisfactory to Tchaikowsky Minor. Orch., his own fresh simplicity for a more fancy in. himself in fashion, with Ormandy. this for he tinkered it telligibility, and I'm not sure I like it. (N.B. for quite some time. This arrangement sets Columbia ML 4939. it Who ever has heard of an orchestra overshadow- for small string orchestra, and the resulting sound becomes ing a piano part on records! Just turn up the It more and more difficult. these slays, compares immediately with the familiar and very solo mike a peg and the piano will overshadow to recapture the free, sensitive Romantic way popular Tchaikowsky music for string orchestra of musicial the orchestra for a fare -thee -well. Ergo (there- expression- Itere is a first -rate such as the "Mozartiana" suite and the Serenade fore) . there's no real need for a recording evocation of Franck, of the sort that combines a in C. The music, dating from the time of the 5th real of this tricked up concert version. Better the feeling for the Franck idiom, the turns of Symphony, is mature, falls somewhere between phrase, the original, as written, and let the engineers do the play of sunlight and shadow, the the "higher organization" of the symphonies and evanescent tricking up, when and if necessary.) changes of key, with a very modern the episodic character of the famous ballet scores. efficiency and intensity. -Don't let me spoil a nice piece for you, on Perhaps this is a bit Very nice, though there's not a trace of Florence, such technical grounds. The recording is big faster and more nervous than Franck might to my ear! have imagined his music and distant, with the piano -unusually -at stage back in the '80s, but it Like most 11f recordings, -GM this one is distance, 'way off, and the music, diffuse and suits us today, and there's not a trace of hard- appallingly dead. (Sound stage recording ?) longwinded or no, is juicy and Romantic in the ness or coldness in it. One of Ormandv's finest Luckily. the string group plays and smoothly best tradition of such works, the Szell perfor- jobs. Recording at a distance, somewhat hollow continuously most of the time, without sudden sounding, but mance equally its the tradition. ultra -clear. breaks, so that the lack of liveness is not too noticeable. A good, professional playing job. Franck: Violin Sonata, Szymanowski: Mahler: Kindertotenlieder; Lieder eines Violin Sonata, Opus 9. David Oistrakh; Tchaikowsky: Piano Sonata in G: Ro- Fahrenden Gesellen. (Songs on the Death Vladimir Yampolsky, pf. mance in F mi., Nocturne and Humoresque, of Children; Songs of a Wayfarer.) Nor- Angel 35163 Souvenir de Hapsal. Nadia Reisenberg, man Foster, bar., Bamberg Symphony, Oistrakh is not only a first -class violinist in the piano. Horenstein. grand tradition; he is a modest and musical Westminster WL 5330. Vox PL 9100

58 AUDIO JUNE, 1955

www.americanradiohistory.com The Mahler songs -with- orchestra are unique, the only important solo songs that are normally treated like songs -with- piano -suitable for any voice, male or female, that can sing them. Indeed, Mahler was such a supreme genius of orches- tration that there is a peculiar close, intimate quality to these wonderfully expressive orchestral accompaniments that is utterly unlike anything else in music. According to our taste today, these i remarkable songs proclaim Mahler a first -rate THE NEW genius, where his huge symphonies (more important by far in his own mind) are increasingly overblown and unsuccessful in modern perfor- HIGH -QUALITY mance. This performance of the two sets of songs is by an excellent and unassuming baritone who LOW -COST sings at seeming stage-distance, his "level" relatively low, and is even occasionally a bit hard to hear. The orchestral accompaniments are FAIRCHILD 255 subdued but very much in the spirit, and with text in hand one can follow Mr. Foster easily and 25 WATT with great pleasure. This arrangement seems to me much preferable to the usual one where the solo voice is close -up and very loud. There's too much of wonder in the orchestra itself. Believe me, if you once get this music in your head you'll never forget it. It has an extraordinary effect. Mahler: Kindertotenlieder. (Bruckner: Te Deum. Kathleen Ferrier; Vienna Phil- harmonic, Bruno Walter. Columbia 5ML 4980. Here's a mighty twin to Fairchild's well as lowest IM and harmonic I've only heard the Mahler half of this disc- dis- credited by Columbia to the kind cooperation of big -power 260 Professional Amplifier. tortion, resulting in exceptionally true London Records -and I am not clear as to The new 255 delivers a full 25 watts natural sound. Superbly engineered, whether the earlier 10 -inch Columbia ML 2187 of the same performers is actually the same re- of undistorted power for the finest the 255 has a controlled frequency cording or an earlier one. Bruno Walter's Mahler sound, best reproduction! response of +0 to -1/2 db, from 20 is smoky sultry, more less and electric, than is Horenstein's, but the two are of just about equal This the ideal power amplifier for to 20,000 cps. interest. My personal feeling is that the late the average home or apartment. The You can always restore "new ampli- Ferrier was a great singer but a one -style artist Fairchild 255 gives you full power fier" performance to the Fairchild who sang just about everything from Italian 255, opera to Mahler with the same noble sincerity; from deepest bass to highest treble, even if tubes age unequally, by Fair- frankly I don't think she really penetrates this and an instrument especially designed child's simple, exclusive distortion - music, though the singing is, as always, noble and Sincere. for minimum transient distortion as cancelling balance control.

Otl'l Tchaikowsky: Manfred Symphony. Philharmonia Orch., Kletzki. COMPACT: Only 6" x 9 1/2' base and 61/2" high i Angel 35167. INPUT IMPEDANCE: 100K Ilere is a big work of Tchaikowsky, often POWER GAIN: 42db cited as one of his important productions, that HIGH SENSITIVITY: less thon one volt input required for full output is rarely heard. The reasons are probably centered, first, on its length -four long movements - and, more particularly, about its pace; for this is one of those works of extreme Romanticism and its only q 50 that take their time almost exasperatingly, for the modern restless ear that wants to get to the point with efficiency. The "story," Lord Byroñ e dramatic poem, is of the sort that is practically incomprehensible to most people today -the Romantic hero wanders murkily from eerie ad- FAIRCHILD 260 venture to adventure, reeking of despair or ecstasy or what -not. The straightforward tale of 50 WATT Romeo and his Juliet is much more to our taste. I tried the Manfred Symphony once before in an earlier recording and got lost in its murky wanderings ; this time things fared much better and the work was enjoyable to the end, partly due, I suppose, to having heard it before; but also. I hasten to say, it was thanks to an excellent performance and superb recording on this Angel disc. If you have an hour or so of leisure and are in the mood, you'll find this well worth a try, as a sort of stretched -out "Romeo and Juliet." It's really a very good piece and When you need full 50 watts of severe transients! And, thanks to there are, incidentally, some fine, big -bottomed Fairchild 260! Fairchild's exclusive distortion- cancel- "hi -fi" passages, as well as plenty of sweet power, get the Tchaikowsky melody. This high -power instrument offers ling balance control, you can always complete stability under all loading restore "new- amplifier" performance. LOOKING 'EM OVER conditions - won't ring with most Stravinsky: The Story of a Soldier (His- toire du Soldat). English version. Instr. only $144.50 Ensemble, Vardi; Fritz Weaver, John Har- kins, Frederic Warriner. Vox PL 8990. Vox put out a version with the original French dialogue and now follows it up with a new recording in English translation. The symbolic "story" (with stage action, originally) seems to me very worthwhile along with the music, adding much meaning to the musical intention; but the trans- IIRCIIIIDEQU /PMENT `O lation into English doesn't come off easily; this one is further hampered by over- acting and 9th AVE. rr 154th ST., WHITESTONE, NEW YORK Hollywoodish mannerisms on the part of the (Continued on page 78)

AUDIO JUNE, 1955 59

www.americanradiohistory.com ^ PHONOGRAPH EQUALIZATION YO.;, n Equipment Report .,Q+ ion ' ! iliái i I ;i lD Q .zn 1 i Pilotrol PA -913 Preamplifier- Equalizer -"Dual" Auto- Ta PosiT10N$ -E SwITGN IC1I"! matic Record Player -Crestwood 304 Tape Recorder. 10 RiAA li AA I-IN -YO AES a I-1 NAB ------16 _ ' OUR FIRST THOUGHT ill seeing the Pilotrol his BOO _.._...... __.._ ß0 put own announcements on a tape along PA -913 Preamplifier -Equalizer for the with a favorite radio program would be first time was that this was an item attractive. that many audiofans would "go for" because . . The Pilotrol consists of a phonograph

p TONE CONTROL . Ii of its appearance and because of what it preamplifier RANGE with separate turnover and would do. That was before we had ever had rolloff an opportunity to play with it or even to controls operated by interlocking inspect the circuit schematic (Fig. 3). pushbuttons, another five -button gang which Gimmicky, perhaps, but down under that serves as selector switch and power control, fancy exterior stands some good engineer- volume and loudness controls, separate bass ing sense and -in our opinion-some good and treble controls, a microphone amplifier product sense. And while the true audoifan with its own volume control, and a cali- J4l:Q will find some of the so- called gimmicky brated output meter which may be used on Eii íiiliiii -- 'nii features extremely useful, he-or anyone either of two output circuits-one of which else-will find that the operation is conve- is intended for feeding a recorder and not nient and that the flexibility offered to the affected by the tone, volume, and loudness Fig. 1. Performance curves for Pilotrol PA -913 occasional tape recordist who may wish to controls, and the other intended for feeding a monitor amplifier and speaker. But the .50 main advantage of the meter to many users will be that of serving as an audio VTVM. g .a0 11111_ 11111iuuuIIIIÌÌIIIIiiii1111 Using certain inputs and with controls set in accordance with a chart in the instruction Ñ 11111 11111 11 III /I. IIIIII u1 =III I. book, signal voltages as low as 165 micro- II I 1 IIImoI!: lm11!1ilm II! ííI volts will give a deflection to the scale "0" 11111 /11111 III 'llllli'ÍI on the output meter. Figure 2 shows the z 111I11 . íiI1111i Ì11I : ÍÌ11 input voltage required to give "0" deflection III I111 /11=11111111 /1111111111 A/4/11111 from four separate set -ups and with the 11i11i111111!111/NOM 11111 six indicated meter switch positions. When .11111=1IIimmo i1111mUaP:immli ll used conventionally as an input amplifier, 11111111iimIIIIImItimmimum111 the meter indicates output voltages at scale 001 01 01 10 "0" of .06, 0.19, 0.62, 1.9, and 6.2 volts respectively for the 0, + 10, +20, + 30, and SIGNAL VOLTAGE AT INDICATED INPUT + 40 positions of the meter switch. For the Fg. 2. Input voltages corresponding to meter switch setting for different modes of connection. With amateur recordist, this unit would find volume and loudness controls at maximum and tone controls flat, IA) is input at Mic jack, with many uses. microphone control at maximum and meter switched to Monitor. (BI is the same as (A) but with Aside from these features, however, the meter switched to Record. ICI is input at radio jack with mic off and meter on monitor. (El is Pilotrol is a good home system input uni . the same as (C) but with meter on Record. ID) is basic meter characteristic. The curves arc quite accurate. the Ilnldness

NEWROPPPIO .. o-.' : 1 Y : I .11101. PG

r P K.-. P 1?"

C ace 0.

yw ... I _w o roe

11 .. ..T

Fig. 3. Over -all schematic of Pilotrol PA -913. 60 AUDIO JUNE 1955

www.americanradiohistory.com and volume controls are separate, tone control curves are satisfactory, and the hum level is exceptionally low -due largely to lgoitelet pea, loatey úe the use of d.c. on the heaters of the first three tubes. On the phono input, the unit KNIGHT HIGH FIDELITY COMPONENTS will produce a 1 -volt output from a 2.7 mv input signal; on microphone, from a 0.65 mv input; on the high -level inputs it designed and built to will give the 1 -volt signal from an input of 0.15 volts. With volume and loudness ALLIED'S specifications controls at maximum, the hum level on KNIGHT High Fidelity components give phono is 54 db below 1 volt, and at normal in settings of these controls the hum level is you the most for your money perform- Knight "Bantam" Hi -Fi Amplifier ing quality, appearance and dependabil- better than 75 db below 1 volt. ity. These are designed and built Performance is excellent throughout, and Compact -no cabinet required. Full 12 units showing watts output; response, ± .5 db, 20- to ALLIED'S own high specifications by the indicator lights which channel 20,000 cps; 3-position record compensa- outstanding makers of hi -fi equipment. is in use are an attractive feature. The tion; loudness- volume control; tape are offered as from its Because these components entire chassis may be removed recorder input and output jacks; micro- ALLI ED'S own private -brand products, case and mounted in a conventional cabinet, phone input; separate bass- treble controls; handsome black metal cabinet with large sav ings are passed onto you. KNIGHT etched gold trim, 33 z 13 z 1034. quality is backed by an unconditional 93 SX 312. Net only $59.50 guarantee for one full year, and a 15-day trial offer with money -back guarantee. KNIGHT gives you the best Hi-Fi for less.

"Golden Knight" 24 Watt Hi -Fi Amplifier Brilliant performance: response, ± 0.75 Fig. 4. "Dual" Automatic Record Player with db, 20- 40,000 cps; less than 1% harmonic distortion at 24 watts; 3 positions of rec- 45 -rpm spindle in place. ord equalization; separate bass and treble controls; 4 inputs; 8 and 16 ohms speaker if desired, the change being made within output impedance. Rich satin gold finish, minutes (after the hole is cut in the new 8 x 14 x 9'. Removable escutcheon for cabinet). Figure 1 shows the performance custom panel mount. ill the various departments. 93 SX 321. Net only .. $79.50 "Space Saver 11" Hi -Fi Phone System Here's authentic Hi -Fi performance "Dual" Automatic Record Player that fits in the smallest available The Dual Automatic Record Player, space. No cabinets required. System includes: Knight 12 watt "Bantam" described again in the PHONOGRAPH EQl'IP- Amplifier, Webcor 3 -Speed Changer MENT section, was tested thoroughly, and (in Russet and Beige or Burgundy the results are listed here. This unit is and Beige) with G.E. RPX -050 mag- planned for those who want to play LP's netic cartridge and dual -tip sapphire and occasional 78's manually, but when they stylus; Electro -Voice "Baronet" en- play 45's they want a changer. This device closure with SP8-B speaker (in Ma- Knight FM-AM Hi -Fi Tyner Blonde). Ready to plug in; is the answer for that need. It is an auto- hogany or ideal "space -saver" tuner. Highly hi -fi record included. Specify colors. matic player in that the user has only to The sensitive drift -compensated circuit with 94 PA 159. Net only ... $157.95 place the record on the turntable and press AFC. RF stage on AM and FM. Loop a button -and the record may be of any for AM. Sensitivity: FM, 5 mv. for 20 size from 6 to 12 inches. As soon as the db quieting; AM, 5 mv. Controls: tun- button is pushed -to select the proper stylus ing and selector. 10 tubes plus rectifier. and start the mechanism-the arm lifts, Measures only 5%j z 133.4 x moves to the center of the record, and 94 SX 728. Net only... .. $89.50 ALLIED'S lowers to the surface of the disc. A small As above, but in black and gold metal rubber tired wheel mounted at an angle cabinet, 6 x 13% x 68-Page Hi -Fi Catalog 94 SX 729. Net only .. $95.50 rolls on the record and carries the arm out Your guide to a complete to the edge. As the wheel falls off the edge understanding of Hi -Fi. of the record, it retracts and lowers the Shows you simply and stylus to the starting groove. When the clearly how to select a Hi -Fi record is finished, the arm is raised and music system at lowest returned to its rest and locked in place, cost; contains many hand- where it remains until the button is de- some do- it- yourself instal- pressed again. Knight Self -Powered Preamp- Equalizer lation ideas. Offers you the world's largest A tip -up crystal cartridge is employed, Efficient, versatile control unit for any selection of complete systems and indi- and pressing the Microgroove or Normal basic Hi -Fi amplifier. Response, t 1 db, vidual units (amplifiers, tuners, speakers, 30- 30,000 cps; 3- position record compen- enclosures, changers, recorders, access- button selects the proper stylus and unlocks sator; 4 inputs; magnetic phono, tuner the arm. or crystal phono, tape, microphone; out- ories) from which to make your money- saving To Hi -Fi, to own put, 2.5 volts; tape output, 1 volt; hum, choice. understand -65 db. In compact black and gold the best for less, write for this FREE book. metal cabinet, 3% z 11% z 5 W. 93 SX 315. Special Price Until r Ì Sept. 1, 1955 $32.95 ALLIED RADIO CORP., Dept. 17 -F -5 100 N. Western Ave., Chicago 80, III. ALLIEDA RADIO Send FREE 68 -Page Hi -Fi Catalog. Ship the following: dowedi $ enclosed

Name Address

Fig. 5. Push buttons select desired stylus and City Zone State start the mechanism. a

AUDIO JUNE, 1955 61

www.americanradiohistory.com The mechanism is well built -being fin- on music. but distortion is apparently low. ished in the European fashion with guild ., 1IIIII M111IIIIM11111.11 This mechanism is apparently a modifi- craftmanship showing up in places where _ CRESTWOOD 304 II1l1111.11.141111111.. cation of the earlier one used in the 400 the user wouldn't be expected to look. á, I i .11311111111111 series, and it is somewhat simplified in Quality of reproduction from the crystal operation. It is easy to load, starts and cartridge was good, and a three position 6m. 11191. stops without making any unnecessary rolloff switch provides some measure of loops, and if the user follows the direc- tone control. l PLAYBACK OUTPUT FROM TAPE RECORDED -ED::, FROM - FLAT "SIGNAL AT RADIOINPUT. tions there is no reason to break tape when With the 45 spindle inserted in the unit, TONE SWITCHES IN OPTIMUM POSITION. switching from FAST FORWARD to PLAY. If the operation was not greatly different from he doesn't follow directions that's his own any other center -drop 45 changer, except for fault. the locating act of the arm. This mechanism The power supply and power amplifier is made under license from the Swedish .,.11I111II 1I11;I11 are constructed on a chassis separate from firm, Luxor, and appears to be sturdy and WWII 1111111 the recorder itself. The preamplifier is reliable. An interesting machine to watch, e IIi = constructed on a printed circuit panel in- in any case, besides sounding quite normal E11l1111!IllIIII= =11111 corporating the switches and the input and having a low noise and rumble content. a o Emir i.a. 11111 stages, and is attached to the top plate. Neither wow nor flutter were perceptible r ;?-?i aittgè I The first stage is a 5879, and it is followed ° I on piano records. otkal oiillll ®. 10) by III ,'1 the two sections of a 12AX7 connected uIlì in cascade. A 12AU7 serves as the bias -e PLAYBACK FROM AMPEK Crestwood 304 Tape Recorder STD. TAPE #9563 oscillator. The power supply and amplifier - TONE SWITCHES FLAT' chassis is conventional in design and It \cas over em- a year ago that we reported ploys a 12AU7 and two 6V6's in pushpull, on the 400 series of Crestwood tape re- together with a 6X5 rectifier. The 12AU7 corder and amplifier- speaker units, and we Fig. 6. Performance for is used in a Williamsonish fashion, with have recently seen and tested curves Crestwood 304 the newer Tape Recorder. the first section as a simple triode ampli- single -case model, the 304. This is an at- fier direct connected to a split -load phase tractive model employing a new drive inverter which uses the second section, and system which is simple to operate and The tone switches-two of the five piano which drives the two 6V6's connected as which also works at two speeds-7% and keys -provide the tone control range pentodes. ips. The unit 3g operates from a set of shown. In the record position, the internal "piano keys" which actuate separate phen- Recording from a signal fed into the olic strips along the printed circuit pre- speaker is switched off, but an external RADIO input and playing back through the to have amplifier chassis over etched copper con- high -impedance output gave the curve speaker may be plugged in so as tacts, thus resulting in an integral switch shown in the upper section of Fig. 6. Con- monitoring during recording from the assembly. As seen in the lower section of sidering the performance from the standard radio, for example. A high -impedance out- the performance curves, Fig. 6, the play- tape, we were surprised at the IN -oui' curve. put is available from the input amplifier back from an Ampex Standard Alignment However, for voice, this is ideal, for the section to permit connection to an amplifier Tape #5563 is reasonably flat from 50 to reproduction is crisp and sharp, and of ex- from a hi -fi system, or for a pair of moni- 6000 cps, with usable response to 8000. cellent clarity. Bass response was lacking toring phones.

To this dedicated hi -fier all is suspect AT HOME WITH AUDIO until it proves itself out. On the score of alert scanning, for example, there is the A -B comparison gambit, between test ( from page 21) pressings and the original recording on tape. Although this is the professional's way with a disc, you yourself can adapt tolerance, are non -inductively wire - Patch? No, Splice . . . the procedure to your own way of liv- wound. Also on the 1 per cent tolerance For owner ing at home with audio when you occa- level the of this system, living are the coupling capacitors, feed- with fine audio sionally dub from a fine LP record to back -shunt results is not a taken -for- capacitors and the phase - granted thing. In his case the ramparts tape. Here's how you might do it: 1) shift capacitors. Transformers are fully of hi -fi Play the record on your well -balanced potted. are always alertly scanned. See The Ultra- Linear output trans- (as in Fig. 5) how he monitors with a turntable with absolutely level tonearm. former is an Acrosound TO -330, 60- set of Permoflux earphones through the Note the point on the disc that has the watt rated at 20 /20,000 cps. Power phone jack on the Ampex preamplifier greatest volume. 2) To avoid overload- transformer is a UTC LS74; UTC also control panel ; on the same panel is a ing the tape, adjust recording level con- is filament transformer T,, giving 6.3 complement of controls for juicy flexi- trol on the preamplifier of the tape re- volts at 10 amperes, center -tapped. Of bility- record switch, record indicator corder so that the VU meter reads the the same brand is filament transformer light, power off-on switch, standard VU loudest possible peak permissible for the TA, which is faced around to give 117 meter, speed equalization switch, input volume of the record. With tape at 7r/z volts for the bias supply, and is rated at selector (for microphone, balanced or ips speed, for example, the maximum 2% amperes. This procedure provides unbalanced line). The meter and output peak with an orchestral selection should adequate isolation from line. a.c. The selector switch connects the meter to in- be set at either plus 1 db or plus 2 db. B -plus smoothing choke; L, is 20H at dicate playback or record level, and With a vocal selection the peak should 300 milliamperes. (Amplifier and power bias and erase current -the latter two be below zero, either -1 db or sometimes supply are shown in Fig. 4.) only when the recording circuit is ener- -2 db maximum peak. (Otherwise dis- The circuitry of the separate power gized. Also provided is a playback -level tortion- unpleasant, unwelcome, and in- supply contains two 6080 tubes as regu- control affecting only the output from excusable). 3) Set tape on "record," lators for B -plus current (equivalent to the tape. Another earphone monitoring start the disc, and the dub is now under- 6AS7's) ; two 83 tubes in parallel to in- operation (as in Fig. 7) shows the owner way. 4) By using the input switch on the crease current capacity; two OB2's used with hands on editing knobs of the tape preamplifier, you now listen to a com- for reference voltages; one 6SJ7 as a reels, moving the tape slowly through parison between the tape and the disc, d.c. amplifier used to control the 6080's. head assembly to spot extraneous noises alternately. It is very important that Filaments are biased with a positive volt- and clicks. Where they occur is noted by levels of both disc and tape be of the which the VU meter age to reduce heater cathode leakage. marking the tape at a point directly over same magnitude, the playback head, then processing on will reveal. This does it, and all of it is Dropping resistors are inserted in each the tape splicing block (as in Fig. 7). herded through the amplifier into the of the plates of the 83's to maintain uni- This hand operation see -saws the tape main speaker system, heard in the man- form conduction. Fixed bias utilizing a through minute lengths so the defective ner of ordinary playbacks. The odds are selenium rectifier gives 130 volts nega- signal or excess noise spots can be ac- you will more frequently be likely to tive. curately located and spliced out. dub from FM to tape, but the procedure

62 AUDIO JUNE, 1955

www.americanradiohistory.com is the same. With foreknowledge 'of the HEATHKIT selection coming in over the air, you should have no difficulty setting your dubbing sights for the same kind of undistorted tape results. "BUILD IT YOURSELF" Dub -a -dub Dub . . . Used alertly and with some practice, you can attain skills in dubbing from amplifier disc to tape to a point where (as we have seen and heard demonstrated) the quality of sound on the one is twin and mirror to the other. But not without the aid of kits your newly fine ear and your "green" hi -fi thumb -the one encased in foam - rubber covered earphones, the other en- eaticizlt sconced fondly on the volume buttons. WILLIAMSON TYPE your for (ACROSOUND To add to talents precision, TRANSFORMER) you might look into the problem of This dual -chassis high tracking error. This can be (if discov- fidelity amplifier kit provides installation flexi- ered) cured effectively if you have well - bility. It features the pickup Aerosound "ultra-linear" engineered and turntable equip- output transformer, and ment. Our reader does it this way : On has a frequency response within 1 db from 10 cps to 100,000 cps. Harmonic distortion the T43H Rek -O -Kut two -speed turn- and intermodulation distortion are less than .5% at S watts, table he places a Cook or similar record- and maximum power output is well over 20 watts. A truly outstanding performer. W-3M consists of main amplifier and ing of a 3,000 -cps note. There's a 220A power supply. Shpg. Wt. 29 lbs., Express $49.75 Fairchild cartridge in the same make eCedee Model W-3 consists of W-3M plus WA -P2 Preamplifier list- 16 -inch 202 arm, which is viscous ed on this page. Shpg. Wt. 37 Ibs., Express $69.50 damped horizontally, with ball -bearing YOURSELF Y point suspension, roller -bearing drive, eatlktt and spring -loaded vertical tension. (A WILLIAMSON TYPE glimpse of this in Fig. 9). The pressure reQticit Here is the complete (CHICAGO TRANSFORMER) of the stylus on the record groove is ad- HIGH FIDELITY preamplifier. Designed specifically for sae with This hi -fi amplifier is con- justed (usually about 8 grams) until the PREAMPLIFIER the Williamson Type cir- structed on a single LP- gaited disc is heard to generate a cuit, it provides equalisa- chassis, thereby affecting tion for LP, RIAA, AES, a reduction in coat. Uses single, pure note. With a vast (really) and early 78 records, 5 new Chicago high fidelity collection of LP's it is not a question of switch -selected inputs output transformer and with individually preset provides the same high performance as Model W -3 listed above. determining this or that stylus pressure level controls, separate An unbeatable dollar value. The lowest price ever quoted for a for any one of them (an impossible bass and treble tone con- complete Williamson Type Amplifier circuit. MODEL WA -P2 trola, special hum control, Model W -4M consists of main amplifier and power .ugq,ly a task), but rather one of achieving either etc. Outstanding in per- single chassis. Shpg. Wt. 28 lbs., Expres, thinimum tracking error or stylus pres- formance and most attractive in appearance. Fulfills every Y 39.75 Model W -4 consists of W -451 plus WA - C sure. The end is requirement for true high fidelity performance. $1 -P2 Pre result the same, but this Shpg. Wt. 7 the $ 9.75 amplifier. Shpg. Wt. 3516x., Express only $5.50 man's angels are all on the side of favor- ing true tracking, for marked tracking s' eatleleit error leads to marked record wear, the WILLIAMSON TYPE stylus having a tendency to ride up on 25 WATT AMPLIFIER the side of the groove instead of center- (PEERLESS TRANSFORMER) COMBINATION W -5M and WA -P2 ing within it. This latest and most advanced Hcelhkit hi -fi The precision turntable is mounted on amplifier has all the extras so important to the super-Gritted listener. Featuring ET-68 tubes, foam- rubber since the extremely low fre- special Peerless output transformer, and new cir- quencies which this system so capably cuit design, it offers brilliant performance by any standard. handles and produces tend to generate Hasa response is extended more than a full acoustical feedback, heard as a rumble. octave below other Heathkit Williamson circuits, along with higher power output, reduced inter - And because the efficient low- frequency modulation and harmonic distortion, better phase responses of the speaker system would shift characteristics and extended high frequency response. A new type balancing circuit makes tend to cause vibration through the floor balancing easier, and at the same time permits a - in this man's establishment, the entire Glaser "dynamic" balance between tubes. .Aside from these outstanding engineering features, the W -5 manifests new physical design as well. A protective cover fits over cabinet which houses the amplifier, pre- all above -chassis components, forming a mist attractive assembly-suitable for mounting in or out of a cabinet. All connectors are amplifier and tuner in addition to the brought out to the front chassis apron for convenience of connection. Model WS consists of main amplifier and power supply on single chassis with protective cover. Shpg. Wt. 31 Iba. t record playing equipment, has been set Express only 5.7S over a one -inch sheet of foam rubber Model W-5 consists of W-5M, plus WA -l'2 Preamplifier shown on this page. Shpg. Wt. 38 tbs. $ 59.50 between it and the floor. Helps. Express only There's no doubt about it : hi -fi homework can be forever. And both time and energy can be conserved only with a program of considered first steps, and suffi- HIGH FIDELITY cient practice, leading finally to confident 20 WATT AMPLIFIER HEATH know -how. The latter means that sooner This particular 20 watt Amplifier com- or later, the dedicated hi -fier will acquire bines high fidelity with economy. Single C O M P A N Y coffee -canfuls of those audio components chassis construction provides preamplifier, A OF DAYSTROM, INC. 4 capacitors, resistors, sockets. And main amplifier and power supply function. MODEL A -9B SUBSIDIARY -the True hi -fi performance ± 1 db, 20 cps to for utterly flexible handling and manipu- 20,000 else. Preamplifier affords 4 switch-selected compensated inputs. Push - pull 61.6 tubes used for surprisingly clan output signal with excellent re- BENTON HARBOR 25, lation of his hi -fi gear, those yards and spouse characteristics and adequate wer reserve. Full tone control action. yards of cord and cable sets some of Extremely low cast for real high fie slily performance. Shpg. MICHIGAN which are shown (Fig. 8). How they Wt. 18 Ibx $35.50 "get their hooks in' is shown in the rear view of the tape recorder preamplifier te FOR FREE CATALOG AND SCHEMATICS chassis (Fig. 10).

AUDIO JUNE, 1955

www.americanradiohistory.com NEW PRODUCTS

Lowell Audio Console. Users of sound within the reach of the average hobbyist, precise description. The Royalton is sup- distribut inn systems of every type will amateur and experimenter. It is practical plied in an attractive luggage -type case find distinct interest in the new line of also for the serviceman as an extra 'scope complete with plug -in crystal microphone Lowell equipment consoles designed espe- for bench use or for application on outside for opera imt from a st nndnrd 117 -t'nit cially for airports, schools, broadcast studios, industrial plants, and similar ap- pllcat ons. Constructed of 18 -gauge steel with gray hammertone finish, the consoles are equipped with a matching heavy -duty linoleum top which serves as a durable work surface. Illustrated is a single- turret model which is available with or without a sliding drawer to accommodate a 16 -in. transcription player. Variations of this

60 -cycle wall outlet. Meyer Scientific Sup- ply Company, Inc., 1672 62nd Ave., Brook- lyn 4, N. Y. 1C-13 Automatic Broadcast System. Automa- tion in the broadcast industry has become a reality with the introduction of the new service calls. For complete techni, ai sp.,i- Ampex automatic programming equip- lications and price information, write to ment which can broadcast a ten -hour 'Che Heath Company, Benton Harbor, Mich. schedule without the need for human as- X -11 sistance of any kind. Basically, the system consists of two electronically- inter- locked tape playback units, one capable Broctaer Compact Tea -Watt Amplifier. of playing eight hours of recorded mate- basic design include 2- and 3- turret con- Printed circuit techniques are used ex- rial from a single tape, and the other up to soles of similar construction. For full de- tensively in the new Brociner Mark 10 four hours. On the first unit is placed tails write Lowell Manufacturing Co., 3030 Audio Amplifier. Included in a single com- program material, either from the sta- Laclede Road, St. Louis 17, Mo. -9 tion's music library or from a network or ! pact housing are a power amplifier, bass transcription service. Spot announcements, and treble tone controls, selector switch, local programs and station breaks are re- Xaight FM -AX Tatter. Notwithstanding corded daily in the station's own studio its modest cost, the new Knight Model and placed on the second machine. After 728 FM -AM tuner recently announced by each segment of program material and Allied Radio Corporation, 100 N. Western after each local announcement, a sub - Ave., Chicago 80, Ill., incorporates many audible tone is recorded. At the end of features that assure fine reproduction of each program segment the electronic musical broadcasts Tuning of FM stations "brain' hears this tone and starts the an- is simplified by means of an AFC circuit nouncement machine. After the announce- that "locks in' stations as their dial set- ment another tone starts t he program. ting is approached. This feature also eliminates drift while the tuner is warm- ing up. Equipped with only two controls-

record compensator and phonograph pro - atnplifier. Moderately priced, the Mark lu is ideally suited for use with tuners, all types of high- quality phono cartridges, :utd for tape recording and playback. A simplified record compensator affords convenient selection of record equalization .nd includes a special position for noisy records; a rumble filter is controlled from the front panel. Frequency response is 20 to 20,000 cps within 1 db and power rating is 10 watts with less than 1 per cent dis- tuning and function selector -the 728 is tortion. Bass and treble controls range designed for use with amplifiers having from 15 db boost to 15 db cut at 50 and full sets of controls. Sensitivity on FM 10,000 cps, respectively. Full power out- is 5 microvolts for 20 db quieting; AM is achieved with 6 my into the phono sensitivity is 5 microvolts for 1 volt out- nputiput or 0.3 volt into the tuner input. Audio -frequency response is 15 to put. Dimensions are 4 4 "h x 10% "1 x 8 "d. 15,000 ± ldb. The function switch is Brociner Electronics Laboratory, 344 E. equipped with a position for disabling 32nd St., New York 16, N. Y. 5 -12 AFC. A tape recorder output jack is af- This see -saw action continues until, at forded for recording programs while they each half -hour, a timing device corrects are being played through a high -fidelity Low -Cost Portable Tape Recorder. The for any slight time deviation in the sys- music system. Complete literature will be new Royalton tape recorder combines the tem and inserts a station break. In a supplied upon request. R -10 advantages of light weight, compactness, recent six-week field test at Station KEEN, and portability. It is especially well -suited all of the advantages claimed for the sys- for laboratory use where observation notes tem were fully realized. Currently 12-day Reath/fit Portable Osotlloeoope. Ex- can he recorded during experimental delivery is being quoted for the equipment. tremely light in weight and small in size, processes, thus eliminating the loss of Included in the $4950 package are two tape the new Heathkit Model OL -1 portable time for hand- written memoranda. Essen- playbacks, a recorder -reproducer for re- 'scope kit employs a three -inch cathode- tially flat response over a wide range of cording local program material, an elec- ray tube and is designed for all utility audible frequencies permits good repro- tronic timer -control unit, and a special functions. Sweep operation up to 100 kc, duction of speech and laboratory sounds, control console. Use of the equipment re- push -pull deflection amplifiers, and im- including bubbling, combustion, and elec- sults in many economies which add greatly color and knob styling are among trical discharges. Recording of laboratory to a station's operating efficiency. Ampex iprovedts features. The remarkably low price of noises may be used to increase value of Corporation, 934 Charter St., Redwood the OL -1 brings the instrument well reports and to reduce time required for City, Calif. X -14

64 AUDIO JUNE, 1955

www.americanradiohistory.com k. HARVEY the House of Audio The NEW w-y ;g , 1--a MAGNECORD REK-O-KUT ° A " ,L . M81 Series Jj O%?IlfnP I 3- Speed, 12 -inch Portable PRECISION TURNTABLES TAPE RECORDER

Represented to be the result of more than 5 years study, these new ecord The basic tope transport mechanism playback units are offered as the closest approach to perfection in turntable operates at 15 and 71/2" /sec. A switch performance. is used for speed Like all Rek -O -Kul units, the t bl is cast Aluminum and selection. Other con. exerts no pull on magnetic cartridges. trots are push- button operated. Accom modales reels The following new features up to 101/2". Frequency have been included: single selector knob for response setting speed: at 15" /sec. extends from 40- 33 Vs, 45 and 78 rpm. built -in retractable hub for 45 rpm 15,000 cycles 2db. Employs heads: records ' 3 erase, record and playback. In -requires no external adapter permanently affixed 3 -speed strobe 'record' position playback head serves os monitor. discs for instantoneous speed checking neon pilot light as 'on /off' indicator Separate record and playback amplifiers special cork- neoprene mot material to eliminate are available thus permitting simul- record slippage rec taneous monitoring from tape. Record tangular deck to fit conventional record changer boards. amplifier hos high impedance, unbalanced microphone input and unbalanced bridge input. Balonced Two identical 50 ohm Rondine models are available which differ only in the type mike input and balanced bridge input available through of motor employed. use of optional plug in transformer. Meter is provided for bias, record and playback. Has cathode follower Rending output. Optional plug-in transformer provides balanced Delux Mode/ R -1214 hysteresis synchronous motor. $11995 600 ohm output. Rending Model 8 -12 with Opole induction motor 74.95 M81 -A Re. order Mechanism in portable case.._..._....._. ..._...... $63500 M81 -AX Some os above but less case, for rack mounting_._.. __ 575.00 New 91X1552 Case only for recorder mechanism (with blower assembly; -- .. _._ ___ ...... _ 62.50 M81 -C Retord /Playback Amplifier in portable cose 245.00 ELECTRO -SONIC M81 -CX Same os above but less case, for rock mount. 225.00 81050 Case only for Record /Playback Amplifier. 28.00 M81 -AC Reorder Mechanism and Amplifier combinor. -: Concert Series portable carrying case_. _ ...... _.._.__.._.... 870.00 Electro Dynamic PHONO CARTRIDGE New

Designed for use only in high quality pickup ores the Concert Series Cor fridge provides performance in home systems equalled only by the Professional unit. As with PILOT other ESL cartridges, the OF Concert Series is built around D'Arsonval moving coil. Dynamic mass has been kept to .001 grams with unusually high. AM -FM TUNER compliance. Frequency response extends from 16 to beyond 30,000 cycles. Intermodulation distortion is immeasurably small. Because of the low output voltage and impedance, a matching step-up transformer may be required. The output of this transformer feeds directly into the A newly designed broadcast magnetic phono input of any convenlionol preamp- tuner fee equalizer. PILOTUNER timing the illuminated MicroMeter for ESL Concert Series l diamond stylus only ..____...._:395 greater ease and accuracy in tuning. FM Model AF -850 Specify .001" or .003 ". Section employs Armstrong duel cascade, limiter -discriminator circuit. Sensitivity is Matching Transformer Assembly Model ESL 201M- consists of an ESL better than 1.5 uy for 20db quieting. Micro -Meter tuning indicator 201 transformer mounted on small chassis with input jock em- and output ploys a laboratory- sensitive micro -ammeter. AFC is continuously variable shielded cable with pin plug from 11.00 complete cutoff to maximum. AM Section employs two stage IF amplifier with selector for either sharp or broadband AM, plus a 10kc cutoff filter. Tuner has dual cathode follower output permitting up to 100 Deluxe 3 -Way feet of interconnecting cable. Power supply is self -contained. Complete with tubes $1S450 Speaker System WHAR FEDALE Loudspeakers The New GRAY RIVEREDGE Viscous- Damped 'Briggs' Corner Enclosure High Fidelity ARM

An ual reproducer system employ- Model 108C ing u recognized high quality components. Consists of Wharfedale W15/CS Viscous fluid suspension 15" 20 watt woofer, Wharfedale provides automatic regulation of both the vertical Super and lateral movements of the arm. Improves tracking 8 /CS /AL 8" mid -range loudspeoker, and minimizeses groove jumping and skidding. Protects records because arm will not drop suddenly. and the Wharfedale Super 5 cone Mechanical tweeter, electrically isolated and balanced by means of a Wharfedale 3. resonance is virtually eliminated. Simple slide -in feature per speaker Crossover Network. mils instant interchange of cartridges, Handles records up to 16" diameter. Has adjustments for viscosity and stylus The enclosure is built in accordance with acoustical specifications pressure. of Briggs, Model famous British designer. Entire front is sand filled for added stiffness and 108C $3995 to eliminate spurious resonances. The performance of this system will o be distinct revelation. Efficient load- HARVEY ing gives clean fundamentals to below 35 cycles. Use of similar material SHIPS EVERYWHERE. Use this handy coupon NI/ (cones) in all three speakers provides smooth response up to the 20,000 cycle limit of the tweeter. Finishes available: Mahogany, Walnut, Fruit I- Wood, Blonde on Birch and Maple veneers. HARVEY RADIO CO., Dept. A -6, 103 W.43rd St., New York 36, N.Y. ( Deluxe 3 -Way Speaker System complete with speakers, Please ship the following crossover, enclosure and specially treated sand $25950

NOTE: I Prices Net, F.O.B., N.Y.0 Subject to change without notice enclose check money order for 5 ,r.cludng estimated shipping rharp's. Unused surplus will be refunded. ESTABLISHED New FREE High Fidelity 1927 Send: Catalog HARVEY RADIO COMPANY, INC. Details of your TIME PAYMENT PLAN NAME...... _..._...... _..___._____.._...... _._..- ...... _...... 103 W. 43rd Street, New York 36 JU 2 -1500 ADDRESS _. .__.._...... __.

___...__...._. -__....._. ... _._...... __.__...... _...Zone _.... State....__...... _....__.... LCity J AUDIO JUNE, 1955 65

www.americanradiohistory.com FIRST AND LAST AND ONLY CHANCE TO SAVE THIS KIND OF MONEY! Browning BC -SW AX Toner. Introduced as the first high- fidelity AM tuner equipped for short -wave reception as well as for reception of regular broadcast stations, the new Browning Model L -600 is a companion unit to the Model L -300 tuner for FM only. As the first tuner to cover short wave, the L -500 opens a new dimension in high fidelity-permits the reception of BELOW C noted symphony orchestras, summer music festivals, and the like. In addition to RADIO SHACK'S REMAINING STOCK OF FAMOUS APPROVED "V -12" t,, 1)_'rIIRr FM -AM

covering the domestic AM band, the unit HI -FI TUNERS covers the international short -wave band of 19 to 49 megacycles. Among its features are: selection of broad or standard bandwidth; 10 -kc whistle filter; sensitivity better than 2 microvolts; built -in high - gain ferrite antenna; cathode -follower output, and built -in power supply. Full specifications may be obtained by writing Browning Laboratories, Inc., 750 Main St., Built To Hundreds 95 Winchester, Mass. Z -15 Sell For Sold For Bonatt Bliorogroove Cartridges. Avail- able to manufacturers of 45- and 33-1/3 - NO, rpm players as well as to individual users, ORDER the new Ronette "Fonofluld" Model RA- 34206 -Q 284P high -fidelity piezoelectric cartridge has extremely low intermodulatlon distor- 7 us. tion. It is of the constant- velocity type X85 X4195 and requires a load resistance of 120,000

* Armstrong -type FM! * Cathode Follower Output! * DUAL Cascade Limiters! * 30- 15,000 cps Response! * TUNED RF Stage FM! * 12 Miniature Tubes! * TUNED RE Stage AM! * Germanium Diode AM det.!

FABULOUS BARGAIN FOR JUST 67 READERS!

FINAL CLEARANCE to a handful of music lovers who recognize A STEAL and act fast! The V -12 tuner was enthusiastically re- ohms. When so loaded it is designed to viewed last Spring by High- Fidelity magazine. Radio Shack custom- feed into any magnetic- cartridge input. ers the world around have thrilled to its fidelity and sensitivity. Other models in the 284 Series have con- Now, because we have reached the bottom of the barrel, and siderably greater output and are designed for improving the characteristics of exist- because we're sold out of the separate (easily built) required 6.3V ing record players. For complete litera- AC @ 4 amps, 190V DC @ 55 ma. power supplies, we've reduced ture write to Ronette Acoustical Corpora- our remaining stock of these excellent tuners at LESS than replace- tion, 135 Front St., New York 5, N. Y. Z -16 ment cost! Other features: miniature 81/4" W x 53/e" H x 8" deep size; AVC on AM; tuning, power, bandswitching controls; neon guarantee! Tape Message Recorder -Repeater. An band lamps; 6 -gang condenser; full standard RETMA ideal adjunct for point -of -sale advertising and for increasing the effectiveness of window displays, the Magneloop Jr. is a continuous -loop magnetic -tape record - Reg. $30 playback device recently introduced by DIAMOND (LP)- SAPPHIRE (78) 4,4Nio Amplifier Corp. of America, 398 Broadway, New York 13, N. Y. Available in two mod- STYLUS FOR G -E RPX -050

Thousands sold last year at Radio Shack's customer- preferred low price! NOW - a new ship- ment of the RPX -050 replacement stylus is available for immediate delivery on EARLY mail orders! Guaranteed first quality; and the LP diamond is a genuine South African whole stone, not a fragile chip or splint. Don't miss out again on this Radio Shack bargain that every hi -fi fan recognizes, for America's most popular magnetic pickup. Order No. R- 6008 -AU. RADIO SHACK CORPORATION 167 Washington Street, Boston 8, Massachusetts and 230-234 Crown St., Naw Haven 10, Conn.

66 AUDIO JUNE, 1955

www.americanradiohistory.com els, Magneloop Jr. affords instant recording and immediate playback without the necessity for rewinding or resetting. An- DO AS THE EXPERTS DO nouncements up to 12 minutes in duration may be recorded on Model A which op- Avoid Costly Mistakes the Most erates at a speed of 3% fps. Model B with -Get from Your Hi -Fi $ a tape speed of 7% ips is able to record up The AUDIO LEAGUE to six minutes and is recommended where REPORT gives you all the facts, good greater fidelity is required. Messages may and /or bad, based on results of latest scientific laboratory and panel be preserved by replacing the easily removable tape -loop cartridge. The speaker listening tests. may be placed at a distance from the record -playback unit which is easily con- cealed. Dimensions are 15%"h x 7%"d x Special Trial Offer-Only $1. 9 "w. Supplied complete with enclosure - Current Reports with comparison mounted 5 -in. speaker, crystal microphone, data, frequency response 6 -ft. speaker cable, and tape cartridge. curves, and the results of listening tests on the following: Complete information will be mailed on request. Z-17 Cartridges: Audak Pickering 140 & 240 ESL 1 Electrosonic Lab.l Ronette 284P Fairchild 215A and 220A Sonotone Stephen' Theater Speaker System. Meet- ing with wide acceptance in stereophonic General Electric Weathers sound installations is the new Stephens Test Records : Cook Series 50, Fol kways FPX -100, Cook Series 10 Model 432 multi -unit speaker system, developed primarily for use in theaters. The Arms: B -J ESL -310 Pickering 190D Ronette system consists of a Tru -Sonic Type P -30 high -frequency driver coupled to a 10 -cell Send $1. for complete file 1 #6, 7 & 81 of the AUDIO multicellular distributor. Crossover fre- LEAGUE REPORT covering above Month y reports cover speakers, enclosures, preamplifiers, amplifiers, pick -ups, arms, turntables, changers, etc. Testing methods described in full. Back issues available from October 1954 in limited supply. $3.00 per year, $2.50 in groups of 3 or more. AUDIO LEAGUE REPORT P. O. Box 55E. Pleasantville, N. Y. Authoritative and Enlightening ..

Acknowledged the Leading Publication quency is 600 cps. Bass response is pro- AUDIO in the Field of Sound Reproduction vided by two Tru -Sonic Type 103LX low - frequency drivers. The enclosure is finished in flat black and is 69 "h x 36 "w x 30% "d. Further information is available 1 f you are novice, hobbyist, experimenter, or from Stephens Manufacturing Corporation, engineer ... if 8538 Warner Drive, Culver City, Calif. you are a lover of music and in pursuit of sound, Z -18 ... undistorted ... AUDIO will be your faithful, reliable companion Pilot PM-AR Tuner. A phono preampli- all the way. You will find fier input with variable loading from no more pleasureable and stimu- 6800 ohms to 100 megohms for precise lating reading than ; matching of the load requirements of all there is in AUDIO absorbingly inter- variable reluctance cartridges is among esting material, valuable the prominent features of the new Model and authentic data, workable de- AF-825 Pilotuner. The r -f section fea- tailed instructions . . . all comprehensively tures sensitivity of better than 6 micro- and yet volts on both FM and AM. The circuit is practically presented. a full Armstrong limiter -discriminator type with temperature -compensated drift - "What to Do" and free oscillator. The input -selector switch "How to Do" will guide your every move through this thrilling experience we call Audio. Each new issue brings New Ideas, New Slants, and Latest Developments ... month in and month out ... twelve times a year.

BE SURE to get your copies REGULARLY. r MAIL this AUDIO Box 629, Mineola, N. Y. Coupon Enclosed is f-I Cheek QMoney Order for S Please send a copy of each new issue of AUDIO for the nest [ i 12 months; 24 months to NOW Please is provided with a position for disabling print AFC when desired. Full control facilities Name are incorporated in the built -in preampli- Address fier, including bass, treble, compensated volume control, and five positions of record City Zone State equalization. The attractive front panel Subscription Is finished in etched brass with maroon price: U.S.A., Possessions. Canada and Mexico: 1 year 54.00; 2 years 57.00. all other countries 55.00 per year trim. Pilot Radio Corporation, 37 -06 36th St., Long Island City 1, N. Y. Z -19

AUDIO BUNE, 1955 67

www.americanradiohistory.com THIS TIME BE SURE with O PEERLESS Quality Transformers Edward ratna11 Canby For mñi_ary requirements, insist on Peerless

transformers for 1. EARTHQUAKE thing ...) you'd have to set up yuur recorder on a neighboring sun or a convenient QUAL TY design and OME ACCUMULATED ITEMS of peculiar low-power star, maybe a couple of dozen interest come first this month. Peculiar light years off to our right, or left ; but let QUALITY manufacture S is just the word for my currently that pass. The scientists would get around that insures constant favorite publication, Emory Cook's Audio it. And so does Emory Cook. Bucket, which gives the latest dope on the He's got hold of signals taken all of a QUALITY control. Cook formula for greater happiness -for thousand miles apart, Hanover, New Hamp- Emory Cook and for a lot of us too - shire and Washington, D. C., which ought through zany audioisms. The Bucket, to be to give at least slightly more than an angle sure, has got ahead of the records them- of maybe .0000001 degrees, enough for all selves for me and so I haven't heard his sorts of useful purposes. Earthquake disc, but that won't stop me What to do with two readings of outer - from mentioning it. Not precisely what you space radio signals taken simultaneously at Grade or grade, class might think, or what I had first imagined this useful angular separation ? Make a (vast crumbling sounds of buildings top- "binaural" record of them ! Reports the for class, Peerless pling, at 10 cps., 500 db.; screams and Audio Bucket, no sooner said than done. agonised cries of the wounded, the crackling The rest is up to you. Now all you have to trans`ormers exceed the flames, fire sirens ...) but simply a disc do to join in the great space derby is to taken by MIL -T -27 requirements. of the very slow vibrations down acquire Cook's Road Recording 5013, and earthquake measuring devices, seismo- play it on your two -headed "binaural" phono graphs, speeded up (I understand) to bring system. them within the audible tonal range. If you hear the bonk and the swishes Now of course if you're going to speed and the space whistlers from the direction up a vibration of 1 or 2 cps into audibility, of your Aunt Jemima's bedroom, first floor you might as well make it sound like an South, you may draw your own conclusions. earthquake, which would suggest to me (the If the sounds are heard to come from the speed -up being entirely a matter of choice) cellar right over the oil furnace, then run a nice, crumbling 20 or 30 cps. average. for your life. Any lower and even the ten-ton speaker is Now it's possible that I've got this all Peerless quality systems would do no better than pump a mixed up. The "sounds" (r.f. signals, I ECONOMICAL, UNIFORM, breeze of air in and out of their ports and should say properly) emanate, or seem to mouths and apertures. Good way to stir up emanate, from the ionosphere, a mere DEPENDABLE. extra ventilation in summer. Any higher centamile or so straight up. If that's where than 30 cps, and the earthquake wouldn't they come from in actuality, maybe Cook be more than a sort of moon- quake, or has a pretty good angle after all. Might maybe just a dump- truck -at- the -town- even be an obtuse one. If so, even the most dump sound. obtuse of binaural listeners should be able Anyhow, this Cook item is the real thing, to figure out that triangulation. Aunt Je- technically speaking, and no tricked -up mima better look out. sound effect. Too bad Cook wasn't on hand You can get the Audio Bucket from Cook for the collapse of the New York Coliseum's Laboratories, 101 Second St., Stamford, newly poured concrete floor last month. Conn., and when you look it over you'll That would have made a gorgeous record see why I keep getting magnetized back THIS TIME have Peerless -210 by 160 feet of steelwork and nice towards Cook's records every so often. sloppy wet concrete dropping some ten Most attractive. quoe on your trans- yards straight downward! The papers said it sounded like thunder -a most unsatis- 2. SEALED RECORDS factory description. Cook could have done former requirements. better than that. 'Twas all of two years ago (I think) Incidentally, Cook's next opus in this that this department took up the cudgels general category is the darndest yet. He's for sealed records. It didn't really seem already tried (reverse of the earthquake) very likely then, but look what's happened. converting the mysterious radio sounds that Sealed records right and left, from all sorts come from outer space into audio, for the and varieties of record companies. But hi -fi man's delight. Now, being a "binaural" there's just one aspect of this interesting man of long standing, he's got the radar - development where the prophet Canby sonar- lofar- navigation bug. Why not locate missed the boat, most indisputably. I hereby 0 PEERLESS these radio emanations by triangulation bite the dust and roll in ashes. (so to speak), taking two measurements For, you see, my sealed records, as I Electrical Products simultaneously, from a respectable space - imagined them, it now appears were strictly distance apart, then calculating direction ? obsolete in one respect. I sealed them (in Now that's the sort of thing that should imagination, of course) with old fashioned - lickum style gum. You wet it and you stick A Division of occur to some of our very advanced ultra secret nuclear specialists and probably has. it. Of course, to get any sort of triangle on Whereas, the up -to -date sealed record, as 9356 Santa Monica Blvd., Beverly Hills, Calif. Betelgeuse or Alpha Romeo (whoops, that I ruefully observe, has left me hopelessly the ultra- modern way of 161 Sixt1 Avenue, New York 13, N.Y. one is an ancient auto; I'm thinking of behind. It uses some super -nova or double start or some- sealing, the rubber -base adhesive.

AUDIO JUNE, 1955 68

www.americanradiohistory.com Now this has very important economic ALDRICH TO BECOME implications. Not for the rubber industry, MANUFACTURERS' REP which is doing OK as far as I know. Rather, for the record industry. In fact the whole significance of the Sealed Record is Thomas B. Aldrich, well known Saks altered, in the most fundamental way. There is not one of us, not a manufacturer, dealer, Manager of Presto Recording Corpora- distributor, record collector, who is not tion, has resigned from that position ef- directly affected by this unforeseen (by me) fective July 1, and will engage in business change in the basic sealing method. for himself as a manufacturers' representa- Rubber -base seals (dare I mention it) tive, specializing in audio equipment in CAN BE UNSEALED. and sealed again., the broad sense -as compared to parts and So, you see, we now have a most in- equipment. Mr. Aldrich has been a rep genious kind of -Sealed record, Super that before, having been in that business from combines in one all-purpose package the attributes of the ordinary (lickum -style 1936 to 1942 when his work was inter- sealed disc and the familiar unsealed variety. rupted by a two -year stretch in the USAF. \Vhat a feat. Returning from the service, he was again And don't tell me this isn't an honest a rep from 1944 to 1947, when he became business either, the record business. I will sales manager for Presto Recording Corp- have no such suggestion from anybody. oration. After all, any dope can tell a rubber -based seal from a stickum -style seal with the flick of a fingernail and the public is beautifully protected. If the seal comes up clean with your fingernail, you have the modern type of sealing. It peels off perfectly, leaving not so much as a trace to mar the factory finish. If it tears, it's stickum-style. And just to indicate to you how straightforward all this modern sealing is, I give you Capitol, which takes the crown and the Oscar for the Direct Approach in customer relations. Capitol's sealed records have instructions right on the seal itself. Instructions for what? For removing the seal, of course! "TO REMOVE SEAL, PEEL TAPE CAREFULLY, STARTING FROM CORNER." That's what it says, right on the Capitol seal. Very good idea, because of course if you peeled it too fast, the seal might be BROKEN. No need to go around breaking seals these days, if you're careful.

p4MtI¡G EYEK-TSq:`

July 18 21- \1USIC- ORA\IA -Music In- 303 0 .aWatt dustry Trade Show. Palmer House, Chicago. AMPLIFIER llitlnfush Aug. 24-26--Western Electronic Show and Convention, I.R.E., Civic Auditorium, San Francisco, Calif. The new McIntosh power amplifier MC -30 is unequalled Sept. 30 -Oct. 2 -The 1955 High Fidelity Show, Palmer House, Chicago. for quality reproduction of high fidelity sound. The basically different, patented McIntosh circuit guaran- Oct. 3-5---National Electronics Conference, tees a new standard for low Hotel Sherman, Chicago. distortion- 1/3% harmonic, 20- 20,000 cycles, even at full Oct. 13- 16-The Audio Fair, Hotel New power output? Hum and noise level-inaudible (90 db Yorker, New York City. below full output). This outstanding performance Oct. 21 -23 -New England High Fidelity assures new listening enjoyment without fa- and Music Show, Hotel Touraine, Bos- ton, Mass. tigue. Quality crafted by amplification specialists for lifetime satisfaction. There's nothing Nov. 3-4-Eight Annual Electronics Con- like the McIntosh. Hear it at your ference, sponsored by the Kansas City dealer's. Section of the IRE, Town House, Kan- sas City, Kansas. Subjects to be covered: Components, Microwaves, Automation, Write today for complete specifications and Audio. (Committee can be reached at P. O. Box 391, Kansas City 41, Mo.) McINTOSH LABORATORY, INC. Nov. 4-6-Philadelphia High Fidelity 324 WATER STREET BINGHAMTON, NEW YORK Show, Benjamin Franklin Hotel, Phila- Export Division: 25 Warren Se., New York 7, N. Y. Cable: SIMONTRICE N. Y. delphia, Pa.

AUDIO JUNE, 1955 69

www.americanradiohistory.com LETTERS (front page 6) camt41 problems involved in the reproduction of I-P records. The frequency and amplitude of the resonant peak is determined by the stylus assembly mass, its compliance, the elasticity of the record material, and the stylus radius. A 3 -mil stylus will not resonate at any troublesome frequency in vinyl, but a 1 -mil stylus will unless its mass and compliance are kept within very strict limits. DAVID B. HANCOCK, 4 West 93rd St., New York 25, N. Y. *Several articles by Mr. White under the title "AUDIO AUDITIES" ran in AUDIO in 1954. FD.

NEGATIVE FEEDBACK (l -,tiuued frwn page 23)

There is a limit, however, to the amount of electrical braking that is desirable. Too much will begin to operate on the signal itself when voice -coil velocity is high, which is to say at low bass frequencies. There are three possible conditions of operation from the point of view of damping. Too low a damping factor will tend to produce a bass frequency response peaked at speaker resonance, with attendant hangover and boominess. Sh, Too high a damping factor will produce a system which has no hangover or reso- ELECTRONIC ORGAN KIT nant peak, but which suffers from bass attenuation. The correct damping factor Think of it! A full -sized concert organ that you build yourself for less than half the cost of a comparable instrument if you bought it factory built. Two will achieve flat bass response within 61 -note manuals and a standard 32 -note pedal keyboard make it possible the capabilities of the speaker, and will for you to play the music you have always wanted in your home, and the also prevent hangover. nineteen stops and six couplers give you complete flexibility of tone. The One may ask, then, why the feedback Schober Electronic Organ is an instrument you will enjoy building -one that circuits of all amplifiers are not adjusted you will be proud to own and ploy. for optimum damping factor and left EASY TO BUILD - EASY TO PLAY - EASY TO PAY FOR that way. What is the need for a vari- Construction is not complicated nor particularly difficult, even though there able control? The answer lies in the fact are many parts to put together. Instructions are clear and complete, the that the optimum value of damping console comes already assembled and finished, and with all mounting factor for a particular system depends holes already predrilled. The woodwork is finished, and the bench and pedal upon the speaker, the enclosure, and the clavier are ready to use. But best of all, you pay as you build -as little as position in which the speaker is placed $22.50 gets yov started. As you finish one section, you can order another, and spread out the cost as long as you wish. in the room, particularly the solid angle HEAR IT IN YOUR OWN HOME -Send only $2.00 (re- into which the speaker radiates. For fundable when you purchase your first kit section) for a example, the danger of over -damping is 10 -inch LP demonstration record which shows you just what your own instrument will sound like when you complete it. One side, played by a professional organist, shows the fine tone of the organ. The other side contains twelve bands of tones, each note of the scale, which you will use for tuning the organ, or for tuning any other EEDBACK PATH musical instrument.

THE 92chtìéeì ORGAN CORPORATION NEW HYDE PARK, NEW YORK o Export Dept. TELESCO, 270 Park Ave. New York 17. New York e THE SCHOBER ORGAN CORPORATION, Dept. 16, 35 Dail Street, New Hyde Park, New York Gentlemen: Please send me your free booklet describing the new Schober Electronic Organ 1 completely. I understand that this places me under no obligation whatever, and that the booklet is to be sent to me at no cost. Enclosed is $2.00. Please send me the Demonstration Record. Also include the credit certificate good for this amount on my first purchase of any Schober Organ Kit sections.

NAME Please print I Fig. 5. Phonograph preamplifier equalization ADDRESS (bass boost) with negative feedback. The reduced CITY ZONE STATE amount of feedback is progressively below a selected transition frequency.

70 AUDIO JUNE, 1955

www.americanradiohistory.com greater when the speaker has high magnetic flux. Modern feedback circuits make possible a damping adjustment for optimum bass operation under given conditions. Genalex

Feedback Equalization -=11_w THE ORIGINAL A tone- control or equalizer circuit provides a transmission path whose gain changes for signals of different frequencies. A particular part of the fre- KT66 quency spectrum can thus be boosted or The name attenuated. GENALEX on the Negative feedback be tube and carton is can used to your guarantee create such a discriminatory signal path. that you are buying We have seen that the first action of the original negative feedback is to reduce circuit KT66 ... world - gain ; if this action is made to vary with famous power frequency we have a tone -control or tetrode, often equalizing circuit. referred to as the finest audio Figure 5 illustrates the use of tube nega- ever made! The tive voltage feedback in a phonograph GENALEX KT66 is preamplifier, providing bass boost to the hallmark of the compensate for the bass -cut characteris- finest amplifiers. tic in records. At higher frequencies It is supplied as the capacitor C is effectively a short original equipment circuit, but as the frequency is lowered in amplifiers impedance of the highest the of C rises, progressively quality. Identical reducing the feedback voltage applied pins and to the cathode resistor, and hence in- connections as creasing the amplification of the circuit. 6L6 tubes. The circuit constants can be designed Only $3.50 net for the particular equalization curve required. For complimentary The use of negative feedback in such fact sheet, write Dept.AX 6 -5 equalization circuits is especially suit- III able, since no extra gain is sacrificed. Qty endorsed BRITISH INDUSTRIES product of the CORPORATION Nonfeedback equalizer circuits must also British lndestries Group 164 Duane Street New York 13, N. Y. sacrifice over -all gain, but do not possess the additional advantages of anti -noise and anti -distortion characteristics.

Comp tloroentt Reqsrsten . . . Positions Wanted and Positions Open are listed here at no charge to industry nor to individuals who are members of the Audio ELECTRONIC Engineering Society. Positions Wanted listings from non -members are handled at a charge of $1.00, which must accompany the request. For insertion in this column, brief announcements should be sent to MUSICA L AUDIO, P. O. Box 629, Mineola, N. Y. before the fifth of the month preceding the date of issue.

4t Positions Open Positions Wanted INSTRUMENTS k Audio Laboratory Engineering Assist- ant. .Must be able to set up, operate and By maintain audio equipment in audio division of major consumer testing organiza- Richard H. Dorf tion; construct auxiliary equipment as required; assist division head and others now learn in In one big volume, you can testing audio equipment sold to the .Il about the intricacies of commercial electronic public. Required: degree in electrical engineering organs, i -eluding the Allen, Baldwin, Connsonata, Ham- or equivalent experience; also mond, Minshall -Estey, Lowrey Organo, and others, together with 3 -4 years experience in audio equipment many smaller instruments. Constructional details on the author's Electronorgan operation and maintenance and some and the simpler Thyratone show you how to build one of these fascinating familiarity with theory and mathematics instruments for form of the author's articles of audio electronics yourself. A compilation in book and acoustics. Salary in Radio Electrorics, brought up to date and with many additions. Price $7.50 $100 up, depending on individual. Send (Foreign, $8.001. resume to Personnel Director, Consumer Customary discounts to dealers and distributors Reports, 17 Union Square West, New York 3, N. Y. RADIO MAGAZINES, INC., Book Division 4( HI -FI Technician. Top -notch man re- P. 0. Box 629, Mineola, N. Y. quired for bench and installation work. Please set-d me copies of Dorf's ELECTRONIC MUSICAL INSTRU- Must have interest and specific experi- MENTS. I enclose check money order for $7.50 each ence in hi -ft, and must have driver's i Foreign, $8.00.. license. Good salary and fine opportunity. Highest references required. All applica- Name tions will be kept confidential. Audio Ex- Address change, Inc., 159 -19 Hillside Ave., Ja- Zone State maica 32, N. Y. City

AUDIO JUNE, 1955 71

www.americanradiohistory.com unprecedented FM and AM reception at a sensible price HAROLD LAWRENCE

Heseltine- Warlock: Man and Sorcerer

N, A QUARTER of a century ago, the duality of his nature, Schumann in- p.lice broke down the door of a vented a pair of pseudonyms which he gas -filled Chelsea flat in London in employed in his critical writings and in his a vain attempt to save the life of 36 -year- compositions. Florestan represented the old Philip Heseltine-the most fascinating active, impetuous man ; Eusebius, the in- and little understood figure in modern trospective dreamer. Around 1920 Hesel- English music. Four years later Cecil tine adopted a new name for himself as a Gray published the first and only bio- composer : Peter Warlock. At first the graphy of Heseltine, thereby setting the pseudonym was nothing more than a practi- tone for future articles, reviews, and studies cal device to secure acceptance and publica- of the man and his music. The book has tion of his music. Heseltine simply wished obvious virtues. A friend and editorial col- to avoid being pigeonholed in the public's laborator of Heseltine for almost fifteen mind as an editor and critic who composed years, had at his disposal a custom quality in a Gray wealth in his spare time. Thus, when a group of of letters, documents, and memorabilia. songs was published under the name of perfect package 4" high Add to this a lively and imaginative prose Peter Warlock, they were received and Here is the tuner that offers you more style and the results are bound to be of judged on their own merits. "It gives me interest. However proximity to his subject great satisfaction," he wrote to a friend, for your money in every way: extraordinary led Gray to some rather distorted con- "to reflect what they [the critics] would high fidelity tone, exceptional clusions, just as when one is standing too have said about these same compositions and gain and selectivity sensitivity, more close to a painting, the brush strokes seem had they been signed Philip Heseltine." high output, beautiful "space- saver" design. to dominate the over -all effect. What From the role of "convenient pseudonym," The RAULAND "GOLDEN GATE" brings emerged from the pages of his memoir was Peter Warlock grew into an extension of you a revelation in FM enjoyment, the portrait of a sort of a Jekyll- and -Hyde a hitherto submerged facet of Heseltine's a new experience in AM listening. character doomed to self -destruction, a make -up. On October 23, 1921 Heseltine schizophrenic with overtones of genius. But had his last shave and began his fourth and with every desirable feature... first, a few words to fill in the background. final beard. With this facial adornment, Philip Heseltine was born in London on Warlock sprang forth, a "lusty, roistering, FM response, ± .5 db, 20 to 20,000 October 30, 1894. Largely self- taught, his swashbuckling, drinking, wenching" in- cycles; AM, ± 3 db, 20 to 5,000 cycles. main influences were Delius and Bernard dividual, as Gray described him. Songs as Sensitivity: FM -5 microvolts for 30 van Dieren, the latter being directly re- Hey Troly loly, Good Ale, and The Bache- db of quieting; AM -5 microvolts for 1.5 sponsible for Heseltine's first published lor, all written in 1922, reflect this "change volts output. Separate RF stage on work, a song -cycle Saudades written in of life." A startling portrait of Heseltine- both FM and AM; 1916 -17. Heseltine's birth as a composer was Warlock may be found in Aldous Huxley's discriminator with dual actually an offshoot of his critical activities. Antic Hay. Gumbril, the novel's hero, buys limiters; Cathode follower As early as 1911 he was devouring old and himself a false beard . . . "Fan-shaped, with 2 outputs; AFC; flywheel new music with astonishing rapidity. His blond, mounted on gauze, and guaranteed tuning: FM di -pole antenna, etc. letters to Delius at the time display a undetectable, it arrived from the wig- fresh and original intellect. In 1920 he maker, preciously packed in a stout card- founded a musical journal called The board box six times too large for it and Sackbut. He later wrote several books, accompanied by a quarter of a pint of the numerous essays, and rediscovered, edited choicest spirit gum. In the privacy of his and transcribed prodigious amounts of early bedroom Gumbril uncoffined it, held it out English music. A passionate student of the for his own admiration, caressed its silki- Elizabethan Age, Heseltine was at the same ness, and finally tried it on, holding it time a perceptive commentator on the con- provisionally to his chin, in front of the temporary musical scene. An article on looking- glass. The effect, he decided im- "space- saver" design Arnold Schönberg, for instance, written in mediately, was stunning, was grandiose. Only 4' high -fits anywhere. 1912 was one of the first exhaustive essays From melancholy and all -too -mild he saw Beautiful charcoal black on that composer's work to appear in himself transformed into a sort of jovial marbleized finish with brass England. Like a famous musical journalist Henry VIII, into a massive Rabelaisian control escutcheons. Also of another day, Robert Schumann, Hesel- man, broad and powerful and exuberant easily mountable behind any tine had a nose for talent ; as Gray pointed with vitality and hair-great eater, deep custom panel. Tuner may be used out, "several composers who are now well drinker, stout fighter, prodigious lover - up to 200 feet from amplifier. known were discovered and helped to Cautiously and with neat, meticulous other Hear the recognition by him before any critic fingers he adjusted the transformation to RAULAND was even aware of their existence." One his gummed face, pressed it firmly, held it "Golden Gate" Toner notable example is Sir William Walton. while it stuck fast-One last look at the at your Hi-Fi dealer, The careers of Schumann and Heseltine Complete Man, one final and definitive con - or writs for details were similar in another aspect. To express statation that the Mild and Melancholy RAULAND -SORO CORPORATION one was, for the time at least, no more; and 3515 W. Addison St., Dept. C, Chicago 18, III. 26 W. 9th St., New York 11, N. Y. he was ready in all confidence to set out."

72 AUDIO JUNE, 1955

www.americanradiohistory.com Thus, Peter Warlock (who incidentally grew his own beard), Philip Heseltine's creation, repudiates the past and, like the galvanized monster in Frankenstein, ulti- riczadaccptd 21eeza -Zeftea.z * mately destroys his master. So goes Gray's theory. Transformers the Finest Audio Peter Warlock: a memoir of Philip for Amplifiers Obtainable Heselfine published in London 1934. was in The quality of Acrosound transformers A few years later, an American composer, is illustrated by the specifications music editor, and Delius-enthusiast named of the TO -330, model, designed for high Robert Beckhard ran across the book and power Ultra -Linear amplifiers. was thoroughly captivated with the life of this strange, compelling figure. The fact

that Warlock was a fervent admirer of 1 db 10 cps to 100 kc Delius and Elizabethan music struck a Over 50 watts clean at any frequency responsive chord in Beckhard whose own 20 cps to 20 kc musical interests parallel those of the J Makes the finest amplifier obtainable London composer. From time on, he that using pp par KT66's or pp 6550's began a search for any music of Warlock that he could lay his hands on -a search, J $39.75 net at leading distributors by the way, that is still continuing; Beck - everywhere hard's collection is now about 90 per cent complete. Although he found Gray's book Other models are available with com- stimulating, Beckhard was disturbed by the parable specifications for most audio requirements. over -dramatic, intensely subjective treat- TO -300 for Ultra- Linear Williamson Cir- ment of the "conflict Heseltine -Warlock." cuits with KT66's, 5881's, etc. $24.75 He was scant also unsatisfied with the TO -310 for Ultra- Linear operation of attention given to Warlock's musical out- 6V6 tubes and EL84 tubes. $18.75 put. Beckhard then proceeded to haunt the Why ACRO ULTRA- LINEAR is best. is ecnlained TO -320 for Ultra- Linear operation of public libraries reading articles on and by in FREE 16 page booklet which is obtainable at 6Y6 tubes. $18.75 your distributor or by writ ,ng direct. This booklet Warlock and his contemporaries. Last contain, 7 lull page, of the finest hig r fidelity circuits TO -350 for 100 watt Ultra- Linear opera- summer he spent his vacation in England available. tion of 6146 tubes. $49.50 visiting the scenes of Warlock's life: Pn

AUDIO JUNE, 1955 73

www.americanradiohistory.com TAPE RECORDING AMPLIFIER

lfrom page .'-1 i ground. Under these conditions the resonates at the frequency of the re- equivalent circuit diagram of Fig. 5 cording bias, forcing the bias current obtains. VIA and V,a are taken into ac- mainly through the recording head RH count by putting and through C, which may be formed solely by the distributed capacity of the egg = (3) -Aek shielded cable connecting the recording where A designates the amplification head. amplifier with the recording As ig. 5. Theoretical diagram shows conditions between the grid of V,., and the plate the impedance of the recording head at when bias is inserted in parallel with signal. of Via. Using (3) : ec,= eg,- ek = -ek- the bias frequency is considerably higher (1 +A) than the impedance of C., only a small Then, finding ek directly from Fig. 5, fraction of the bias will appear across After the bias voltage across the recording amplifier has been reduced to (e +pees) gp. _ the output terminals of the recording ek = amplifier. On the other hand, L repre- its minimum, the residual voltage ap- gw + Gk sents practically a short circuit at all pearing at the grid of V. (Fig. 3) could [e-µek(1+A)] gp, audio frequencies, providing an efficient be further reduced by employing a gp,+Gk ground connection for the audio cur- high -mu pentode, as its amplitude is egp, rents flowing through the recording Therefore ek- approximately e. A second considera- (p9p.+g1p1++ head. C. serves the additional purpose µ ¡¡ of tuning the recording head to a fre- tion in choosing an output tube for a +Ak/ particular recording head will be the if A1. current requirements of the latter which µ(1 +A)' BIAS RH are determined by the ampere turns e A (c. necessary to drive its core into satur- Using (3), eg.- CABLE FROM ation. (t(1+ A) L REC AMPL e APPROX (4) 35MH RESONANT WITH L AT BIAS FREO The Final Amplifier This last expression reveals that a volt- The complete diagram is shown in e Fig. 7. The mentioned feedback path age - will appear at the grid of V. if Fig. 6. The author's series -bias system employs consists of R., R,, and C.. The current a resonant circuit to keep bias out of amplifier. amplification at low frequencies is de- a signal of amplitude e is applied to low- frequency mentioned termined by R.+ R., the its plate The previously by the time constant R.C. and method of feeding the supersonic bias quency somewhat beyond the highest turnover frequencies which may still be the high -frequency turnover by the time into the recording head in parallel with audio R,R,. procedure for the audio frequencies would therefore recorded without attenuation. This will constant The design this network and Cr, in Fig. 6 will now result in the appearance of a consider- provide some additional treble boost of bias at the grid of which may be utilized to compensate for be described. able fraction the An audio generator is connected to V. and the danger of crossmodulation the losses occurring at the high audio - recording Even the frequencies. As it is very desirable to the input terminals of the with the audio frequencies. and output amplitude of the bias fre- make C. as large as possible in order to amplifier, the insertion of a filter for' the playback amplifier is plotted in quency between the recording head and reduce the bias appearing across its decibels against a logarithmic frequency the amplifier would meet with difficulties terminals to a minimum, its value resulting in the most satisfactory response scale for an input signal of varying fre- owing to the high output impedance of is should be carefully determined. A quency and constant amplitude. It the amplifier. now necessary to correct the bass re- The recording bias is therefore fed further increase of C, is not advisable, with as it would seriously affect the high sponse of the playback amplifier prior into the recording head in series the recording amplifier. audio frequencies, as shown in Fig. audio- frequency response of the am- to adjusting the After this has been accomplished, the 6. The parallel tuned circuit L - C, plifier. procedure is the following: (1) The playback amplifier output is plotted using a purely resistive feedback RIO - 22,000 impedance R =R. +R, (see Fig. 8). 300V (2) The region in which this fre- W 1B quency response drops by about 6 db RI 4 7 R8 per octave may now be extended, ad- CI-.05 o C3. 05 o C5-05 a-K--4+4OUTPUT justing C. (Fig. 6) to its optimum 65 value. 6SL7 (3) The frequency f, at which the V2 I output is 3 db below flat response, and INPUT vu Ws'. the frequency f. at which the response drops by at least 6 db' below the 6 -db- W t per- octave line, are found by inspection. La W R7 iJ R9 (4) The value of the components may C2 î ] 1C4 N now be found from f,, f. and R accord- ó= é ;R2 R3 - f R5 25 R6 ing to the formulas 12V O Ta39 R.-R f' R,= f, + f. R ; and C. = 1 f'+ f. 24,R,' Fig. 7. The complete tape-recording amplifier. Output goes through a shielded cable to the head and bias -injection arrangement of Fig. 6. 1 This latter point is not critical.

74 AUDIO JUNE, 1955

www.americanradiohistory.com These values may further be modified by trial and error according to the final over -all frequency response. The values of the rest of the corn - ponents are not critical. However, care should be taken in choosing the C.. The slightest leakage through that capacitor Centralab's will cause direct current to flow in the recording head, and the resulting. pre - magnetization will cause the signal -to- Junior COMPENTROL noise ratio of the recording to deteriorate considerably. The recording head employed by the author has the following characteristic: impedance, 0.44 by measured at 50 cps, resonating at 14,000 cps with 200 µµf; maximum impedance (self- resonating) at 60,000 cps However, any high -im- c pedance head may be employed with the corresponding changes of the critical components R., R., C., and C. (Fig. 6). In the present design their value was chosen for a tape speed of 7.5 ips. A conventional reproducing amplifier was employed and yielded at that speed an over -all response of ± 3 db between 40 and 10,000 cps. The highest frequency Junior Compentrol is a volume obtainable without attenuation will control with special Printed Electronic mainly depend on the kind of recording Circuits. It automatically bolsters head, reproducing head, the tape speed, high and low frequencies otherwise and the tape itself. The recording am- often lost. You get greater pleasure from your radio set, audio amplifier, or plifier itself is capable of amplifying the % or 1 Meg., phono combination. Ask your Centralab less highest audible frequencies with con- distributor - or service man. Write switch - - $2.50 net siderable preemphasis, and with remark- r,¢ or 1 Meg., Centralab, Dept. 934F. Milwaukee 1, with . - able lack of distortion. Wisconsin for Compentrol booklet. switch 53.00 net

.-.

TREBLE BOOST OWING TO C.

RESPONSE OF COMPENSATED AMPLIFIER control preamplifier -equalizer C2 (FIG 6) CONNECTED

RESPONSE WITHOUT OCTAVE ANY COMPENSATION LINE

f, f. FREQUENCY

Fig. 8. Playback- cmplifier output curves under various adjustment conditions.

HIGH -POWER AMPLIFIER Owners of the Marantz Audio Consolette invariably comment on (froto page 17) the immediate improvement in sound quality of their systems. Such a fine instrument cannot be produced by the thousands, but only through care- the 100 -ohm final -tube plate- current balance control to its middle position, set the ful aseemhly and thorough testing of each unit. slider on the 200 -ohm final -stage bias Naturally, its components are uncompromisingly resistor nearest the cathode end and choser. for superior quality. This and the character of screw up fairly tightly the trimmer its wo-kmanship makes it the obvious choice for those across the 24,000 -ohm feedback resistor. who Apply plate and filament power. After wish to improve their present installations. Chassis suitabæ for installation with 5 or 10 minutes warmup, adjust the $142.50, cabinet $155.10). dynode voltage for the EFP -60's. With a d.c. voltmeter connected from dynode 'Write for Complete Details: 44 -15 Vernon Blvd., to ground, slowly move the slider on the S. b. maranta L.I.C., New York 60,000-ohm resistor away from the

AUDIO JUNE, 1955 75

www.americanradiohistory.com grounded end. As the slider is moved, the 3 -30 -µµf trimmer across the feedback the voltage will rise slowly at first, and resistor might have to be changed to then jump abruptly to a value of about insure the greatest stabilitiy at high 170 volts. Leave the slider in this posi- power levels. tion for the time being. The sudden It is advisable that a high -pass filter AUDIO_ jump in voltage means that the tubes be incorporated somewhere preceding have commenced their secondary emis- the amplifier. The extended low -fre- SAVE sion and the secondary cathodes are quency response of this amplifier, drawing current. coupled with the fact that the output Adjust the d.c. balance by placing the transformer power handling capacity 25% 11.T::il voltmeter across the plates of the EFP- drops off at the rate of twelve db per 60's and adjusting the 2,000 -ohm d.c. octave below twenty cps, makes the am- balance control until there is no voltage plifier especially susceptible to overload differential. There will be some constant at frequencies below, say, 10 cps. It is random fluctuations of the meter needle conceivable that record eccentricities, This is oui due to supply and tube fluctuations. rumble, etc., will cause the output trans- These should be disregarded. former to saturate at these extremely low GROUP SUBSCRIPTION PLAN Connect the intermodulation analyzer frequencies, thereby generating distor- and adjust the amplifier for about 50 tion and overloading the loudspeakers. Now you, your friends and co- workers watts into a noninductive load. Adjust It was found that at high power levels, can save $1.00 on each subscription the 500 -ohm a.c. balance control for parasitic oscillations appearing on the to AUDIO. If you send 6 or more sub- lowest intermodulation at this power tips of the linearity characteristic caused scriptions for the U.S., Possessions and level. Remove the KT -66's from their the intermodulation to rise to very high Canada, they will cost each subscriber sockets. Feed a very small 60 -cps signal values. It seems that even though the $3.00 each, l/ less than the regular one year subscription price. Present to the input, and adjust the signal's frequency of these oscillations is way subscriptions may be renewed or ex- magnitude until a signal of about 25 volts above the audio spectrum, they have a tended as part of a group. Remittance is measured at the output of the EFP- very drastic effect on the distortion char- to accompany orders. 60's with an a.c. v.t.v.m. Be careful acteristics of the amplifier, and their to isolate the test leads from the ampli- complete elimination is of paramount fier input or feedback oscillations will importance. Even faint wisps and wig- AUDIO is still the only publication result. Readjust the dynode voltage of gles seen only on a wideband, triggered - devoted entirely to the EFP -60's for maximum gain, i.e., sweep oscilloscope have a great effect maximum voltage output. Leave the on the distortion. The mechanism of Audio slider set at that position. Readjust the these effects has yet to be investigated. Broadcasting equipment d.c. balance. Replace the KT -66's in the The harmonic distortion of the ampli- Acoustics same sockets as before, reconnect the fier is less than 0.5 per cent at 20 cps Home music systems intermodulation analyzer, and again ad- at 50 watts. It decreases rapidly as the Recording just the a.c. balance for lowest inter - frequency is raised, and is too small to PA systems modulation. Balance the static d.c. plate be accurately measured at 100 cps at 50 Record Revues currents in the output transformer by watts. At no frequency between 100 cps Please print adjusting the 100 -ohm final balance and 20 kc does the harmonic distortion potentiometer for zero voltage differen- exceed .05 per cent at the 50 -watt level. Name tial across the plates of the KT -66's. Some experimentation has been car- Address This adjustment is very important as ried out with the use of tubes other d.c. magnetization of the output trans- than KT -66's. 807's, 5881's, and the new former core causes its low- frequency Tung -Sol 6550's have been tried. Of T] New Renewal characteristics to deteriorate badly. these, the 6550's are the most promising. Connect an oscilloscope to display the The 5881's cannot deliver the high Name input- output characteristic of the ampli- power without being overloaded, and Address fier at 1000 cps. Increase the input to the 807's, although capable of delivering the amplifier until it is on the verge of more power than the KT -66's, are very New i1 Renewal overload. Adjust the trimmer across the susceptible to r.f. parasitics and are not feedback resistor to eliminate the para- recommended. A single pair of 6550's Name sitic oscillations at the tips of the lin- can deliver almost as much power as four Address .. earity characteristic (Fig. 4). There KT -66's, and they seem to be much freer should be a fairly broad range to this from parasitics than even the KT -66's. 17 New El Renewal adjustment. Reconnect the intermodula- Since the Acrosound TO -330 is not tion analyzer. Adjust the input for 50 matched to these tubes, maximum power,

Name . watts output and finally readjust the in this circuit, is delivered only when a Address cathode bias on the KT -66's (with the different value of load resistance from modulation. These adjustments, if car- the nominal values of 4, 8, and 16 ohms - is a load n New -_ Renewal ried out properly, should yield an inter used. It was found that with modulation distortion figure of less than of about 11 ohms at the 16 -ohm tap, the Name .09 per cent at 50 watts, using 60 and amplifier delivered the most power -in Address 7000 cycles mixed 4: 1. It should be this case about 68 watts maximum. The noted that the a.c. balance is a fairly distortion with two 6550's was not quite critical adjustment for lowest distortion [T] New ' Renewal so low as was obtained with four KT- and should be readjusted periodically 66's. as the tubes age. Whenever the a.c. bal- Name The author is greatly indebted to Mr. ance is adjusted, the d.c. balance should Address Com- be touched up. It is important that dur- David Hafler of Acro Products pany for his many suggestions, and in ing all these adjustments the 1 -ohm T New O Renewal damping- factor control should be set particular for the suggestion to eliminate with its moveable arm grounded. one of the cathode followers in the cross - U. S. Possessions, and Canada only coupled inverter. Also the author would RADIO MAGAZINES, INC. like to thank Professor Earl W. Keller Operation of the M.I.T. Electrical Engineering P. 0. Box 629, Mineola, N. Y. The writer has found that with differ- Department for the generous donation ent speaker systems the adjustment of of his time, advice, and encouragement.

76 AUDIO BUNE, 1955

www.americanradiohistory.com LONDON LETTER (from page 10i Your which is to be marketed later in the year, watts. The speaker systems contained in they could give no details of the cost and each cabinet comprised a wide -angle elec- explained that the first three items which trostatic ribbon speaker, taking an input had been reproduced in the studio had been of 140 volts rms and a 13 % -in. elliptical from their standard recording tape ma- speaker enclosed chines which operate in a 3% cu. ft. critically at 30 ips. The dance damped enclosure, the -all band had been reproduced from a tape at over resonance of the whole system being 47 Nigh 7% ips but the equipment used had been the cps. The bass modified large E.M.I. tape recording ma- speaker was designed to cut off at 6000 cps. chines which they sell to the B.B.C. and No capacitative or inductive components other Recording Companies and cost nearly were required as in conventional crossover $3,000. system. The wide angle ribbon speaker was stated to give a high -note diffusion over an Stensosonic Tapes in U.S.A. arc of 60 deg. Summarising the demonstration, your Fidelity No price could be quoted for the stereo - correspondent can say that whilst it was sonic tapes but it was stated that these could indeed interesting, hearing in a studio a be played on any suitable double track ma- carefully pre-arranged performance of what chine operating at 7% ips with the heads were possibly the original tapes reproduced on the same level. It was claimed that they on studio equipment is very different from would give better reproduction than the listening to duplicated tapes on commercial tapes which are now being nfade by R.C.A. equipment in the home. in America and presumably British tapes No definite statement could be obtained !yIm will be released in the U.S.A. under either as to whether the stereosonic tapes are the R.C.A., Angel, or Capitol marks, al- going to be only the same relative price as though no definite information could be the present English single -channel recorded gained regarding American marketing plans. tapes. Even if they cost no more per foot of It was stated that H.M.V. reproducing music, it must be remembered that two equipment would be offered to the public tracks of the same performance will cost at the National Radio Show which opens double that of single -track tapes. If no rein London at the end of August. The proto- duction is made, it will mean stereosonic will types of the equipment were on view, al- tape records will inevitably be very expen- though no opportunity was given of hear- sive and only the larger rooms could house ing tapes on the machines. The reproducing the equipment which will be marketed by equipment is housed in two identical con- H.M.V. soles of which one contains the tape deck, It may well be that there will be consid- two preamplifiers, one 10 -watt amplifier, erable modification in the design of this and one loudspeaker system, Sound while the other equipment before it is placed on the market. contains the three -speed record changer, Owing to the peculiar position in England the second 10-watt amplifier, and a dupli- regarding purchase tax, it would seem that cate loudspeaker system. one of the consoles would be subject to tax By switching arrangements it is possible because it contains a record changer, whilst to use the two consoles for the reproduction the other console would not be subject to of stereosonic tapes on both speakers, sin- tax because at the present time, tape record- gle channel reproduction of tapes or disc ing or reproducing equipment does not bear records on both speakers, &llr or on one speaker. tax. In addition to a volume control there are It seems likely that some other tape re- bass and treble controls giving approxi- corder manufacturers may well market a mately 12 db lift or cut at 50 and 10,000 more economical arrangement whereby one cps respectively. The balance control en- cabinet would contain the tape deck and two with a ables the sound image to be centralized be- amplifiers and the loudspeakers could then tween the two speakers as may be required be housed in individual cabinets. Such an by the acoustic conditions of the listening arrangement would probably be entirely free room. It was stated that the 10 watt main of tax. If it were desired to reproduce amplifiers did not have a total distortion disc records, then the mechanism could be of more than 0.25 per cent at 8 watts and housed in yet another cabinet which could a noise level at least 55 db down on 10 be connected up to one of the amplifiers.

TO HELP YOU SELECT THE CORRECT HI -FI ENCLOSURE made in Send for this free england booklet. It contains all KARLSON the facts you need lo ULTRA -FIDELITY select and install the ROCKBAR CORPORATION Dept. HF -I enclosure for the dis - 215 East 37th Street, New York 16, N. Y. criminating...the en- ENCLOSURES closure by which all Please send complete description of others are measured. Goodmans High Fidelity loudspeakers.

KARISON ASSOCIATES, INC. Nome DEPT. 8 1483 Coney Island Ave., Brooklyn 30, N. Y. Address Please send copy of your latest book "The Norlson Esrlosure" to City Zone State Name Address My Dealer is City State

AUDIO JUNE, 1955 77

www.americanradiohistory.com HIGH FIDELITY RECORDS CLASSIFIED page 59) Rates: 10c per word per insertion for noncommercial advertisements: 25c per word for commercial advertisements. Rates are net. and no discounts will be three voices. though the result is still worth- allowed. Copy must be accompanied by remittance in while, as compared to no spoken text at all. Beautifully recorded, both instruments and voices. full. and must reach the New York office by the first of the month preceding the date of kiwi.

I Stravinsky: L'Histoire du Soldat )suite); Octet for Winds; Symphonies of Wind Instrs. Instr. Ensemble, Stravinsky. THE AUDIO EXCHANGE has the largest Columbia ML 4964 selection of new and fully guaranteed used equipment. Catalog of used equipment ou Here is Stravinsky's own present interpre- request. Audio Exchange, Dept. AE, 159 -19 tation of the "Soldat" music, minus texts. I Hillside Ave., Jamaica 32 N. Y. OL 8 -0445 AF -860 AM -FM PILOTUNER would not say it is "definitive " -because I have AUDIO EXCHANGE EXCHANGES AUDIO The Ultimate in engineering skill his own priceless older 78 -rpm recording, of the TUBES-70% to 90% DISCOUNT. Govern- very early 1930's (I bought it brand new), and ment, manufacturers, jobbers, etc., surplus. and the sensitivity - symbolic of it is quite different in many ways. But this is Guaranteed 1 year. Free catalog on request. comple'e ire of superb from the horse's mouth just the same, and the Cadillac Trading, Dept. A, 231 -07 Linden Blvd., Jamaica 11, N. Y. Pilotuners. reverse carries a sonorous collection of other works for a similar small group of instruments, SALES-SWAP- SERVICE on all types of new and used audio equipment. the whole recorded in a perfectly huge liveness ARM'S SERVICE COMPANY for a big, fat sound. (The old "Soldat," inter. 235 Lyons Avenue estingly, was one of the deadest recordings Newark, N. .1. WAverly 3 -3025 acoustically I've ever heard.) 25-50%. DISCOUNT. Factory fresh guaranteed PILOTUNERS LP records, 69e and up; send 204 for cata- Or Stravinsky: Pulcinella: Divertimento logue. SOUTHWEST RECORD SALES, Dept. (Baiser do la Fée). Orch. Nat. Radiodif- A, 4710 Caroline, Houston 4, Texas. Markevitch. HIGH FIDELITY SPEAKERS REPAIRED fusion, Amprite Speaker Service, 70 Vesey St., New Angel 35143. York 7, N. Y. An interesting pairing of two works by S. both AMPLIFIERS -HI -FI 45% off 40,000 cycle amplifiers, recorders, based on music by other composers-Pergolesi pianos, organs, accordions, typewriters. molve and Tchaikowsky. Stravinsky's re- writing of these equipment, binoculars. Amazing bargains! men into his own idiom is unique and wonderful ABELMART, 400 Belmont, Paterson 2, N. J. to hear, adding a very understandable and corn - FIDELITY UNLIMITED COMPANY: Au- fortable modern "spice" to the solid musical thorized distributors of SCOTT, FISHER, ideas of the earlier music. Roth performance and PILOT, GARRARI), REK- O -KUT, ELEC- recording are tops to my ear, with some mar. TRO- VOICE, REEVES, HARMAN-KARDON. Complete AA -904 PLOTONE AMPLIFIER velous instrumental sonorities. An outstanding FAIRCHILD and many others. disc. stock, all inquiries promptly answered. Ship- World famous Ultra- linear Wil- ments l'REI'AID and INSURED in USA. tri- Write today. 63 -03 39th Ave., Woodside 77, liamson circuit - an electronic .5 Prokofieff: Flute Sonata, Opus 94. N. Y. Dept. AE. umph characteristic of the (Roussel: Flute Trio, Qpus 40.) Doriot 6- Element Broad Band FM antennas. All wide range of Pilotone Anthony Dwyer, fl., et al. seamless aluminum. $10.95 ppd. Wholesale Supply Co., Lunenburg 10, Mass. Boston B -208 Amplifiers. BUILD YOUR OWN -AUDIO FILTERS This is the original of a well -known and often. -CROSSOVERS played violin sonata; Prokofieff rearranged it Toroidal Inductors give highest "Q ", mini- from flute to violin. The flute version is highly mum size. Molybdenum Permalloy cores wound accurately to requirements, most PILOTONE AMPLIFIERS attractive, as played by the young lady First your sizes $3.00 each. DONALD C. HARDER CO., Flute of the Boston Symphony, with Sanroma at 3:.338 India St., San Diego 1, Calif. find the fiddle version' an in- the piano. (You'll FOR SALE: Shure 55-S Dynamic Micro- teresting comparison -Isaac Stern and Szigeti phone, $35 l'resto TL -10 Tape Mechanism, have done it, among others.) Close -up flute; 7% and 15 ips speeds, $50. 24 Aluminum 10%" piano in background. reels, $1.50 each. All items guaranteed new condition, priced F.O.B. V. R. Hein, 418 la Gregory, Rockford, III. Prokofieff: Symphonies #5, #1 ( "Clas- PRESTO Model "Y ", 2 -speed portable re- sical") . Concerts Colonne, Horenstein. corder, 75 -A table, 1 -D cutter, 112 and 224 Vox PL 9170. lines, GE turnaround playback, 87A amplifier, and monitor in split case, like new. $375 FOB A worthwhile pairing, the lyric little First or Omaha. Chas. F. Craig, 3802 Grand Ave.. PA -915 PILOTROL "Classical" and the lyric big 5th, of a quarter - Omaha 11, Nebraska. Professional Preamplifier - century later, but though the "Classical" is very ENJOY THE FINEST-Magnecorder M -90 well played, the 5th gets what seems to me to Equalizer, an innovation in audio Portable recorder like new, 30% off. Patton be a strident, Tchaikowsky -like performance, 1259 Third Avenue, S.E., Cedar Rapids, Iowa. control -ard other fine products, stressing the grosser aspects at the expense of HI -FI EQUIPMENT: Meissner 9 -1091C AM- including +e portable Encore; much vital detail -work. I don't like it (even if I FM 18 -tube tuner, $125; ACA -100DC direct - did write the accompanying notes) but Horen- coupled Amplifier 20 -20K cps flat, $75; Radio reflect the Pilot stein is no fool and you'd better try for yourself Craftsmen RC -100A TV tuner, 17" tube, $125; "Sandard of if you like the symphony. Altee Lansing 815V speaker system with 2x4 cells, 8018 driver, and 15" L. F. Spkr. Com- Eaellence." plete with Network and field supply. $125: Prokofieff: Piano Sonatas #6, #7. Robert McIntosh 50W -2 Ampi., $200; McIntosh AE -2A Cornman. Equalizer- l'reamp., wood cabinet, $50. Write FOR TECHNICAL DATA AND for information and other equipment. I. A. London LL 902. Etlers, Gladhrook, Iowa. BROCHURE, WRITE TO: The Cornman teduietue a. plculy dazzling (as Enthusiastic collector desires corretape- is necessary for these difficult works) but to my spondence with others with similar interests. ear the musicianship isn't as impressive; this is Heiden, New Brunswick, N. J. more piano playing than it is Prokofieff playing. Western Electric 124E Amplifier, rack Part of a series on the Sonatas. mounted, late model. Excellent mechanical and electrical condition, $85. J. Harris, 11644 Montana, Santa Monica, Calif. GR 8- 1352. VARITYPING Composition Service, DSJ, FOR SALE: Rek -O -Kut TR -12 Recording IBM, paste -up, ruled forms, advertising lay- turntable with M -12 overhead cutter; extra out In English and foreign languages. Cath- cutting head; two feedscrews, for LP and .A RADIO CORPORATION erine Rein, 874 Broadway, GRamercy 7 -5720. standard. Six sapphire cutting styli, and FOR SALE OR TRADE: McIntosh 50W -2 panel for switching from speaker to cutter, 37 -06 36th Street amplifier in factory carton. Need good basic with meter, and jack for monitoring with or Concertone headphones. Everything perfect condition. Long Island City, N. Y. tape recorder -Magnecordette Cavaseno, 6161 62nd class. Box CK -2, AUDIO. First $150 takes all. Jim Ave., Mlddlevlllage, N. Y. . in PRESTO 6 -N, two -speed recorder port TO BUY new copy of Victor 1 -11 NEW 112 and 224 line WANTED able case, cutter, 1003. Send to George outside-in feedscrews, also 112 line inside -out LOC- "Seventeen." price feedscrew, GE turnaround playback, 87 -A re- Kershner, RFD 2, Springfield, Ohio. cording amplifier and monitor speaker in split FAMOUS ENGLISH QUAD amplifier, case, perfect condition, $485 FOB Omaha. Wharfedale speakers. Siemens Radio, Records, Chas. F. Craig. 3802 Grand Ave., Omaha 11, Cabinet. Sacrifice. Phone LO 8 -4729 (New Nebr. York) or write Box CK -1, AUDIO.

78 AUDIO JUNE, 1955

www.americanradiohistory.com PROFESSIONAL 9oichabut Peatzle... LEONARD RADIO DIRECTORY Nate Pinsley, president of Espey Mfg. PROUDLY PRESENTS... Co., :nut Michael Muckley, sales manager, were joint hosts at a trade showing to -LIVINGSTON- introduce the new Espey hi -fi tuners, amplifiers, and complete chassis; exhibit was held during the first week of May at "BI -FI" Espey's New York headquarters . An- other May event occurred on the sixth FOR YOUR LISTENING when Bert Whyte, well -known record ea«li«uacwly Sc«ce 7944 - critic and audio consultant, and partner PLEASURE David Hollister held formal opening ceremonies for their House of Hi -Fi in Man- hasset, N. Y. Inviting in every respect, the HOLLYWOOD ELECTRONICS "House" handles equipment of most lead- 0I DISTRIBUTORS OF HI-FI COMPONENTS ing manufacturers, and is the latest of the country's hi-fi centers catering pri- aCLUSivut marily to the suburban set. New officers of Mark Simpson Manufac- turing Co., Inc., are: Miryam Simpson, president; mark Simpson, vice -president 7460 Melrose Ave los Angeles 46,Calif WEbster 3-8208 and secretary: Bernard :Daman, vice - president and treasurer: George Watson, vice - president, distributor sales division; Pbllltp S. Optner, vice -president, manufacturing division, and Ralph Aasen, vice - president, engineering . . Lawrence W. Mango, since 1949 general sales and mer- chandising manager of RCA Victor Record HIGH -FIDELITY HOUSE Division, has been named vice -president Most complete stock of Audio and operations manager, reporting directly to general- manager Manie Sacks . . . components in the West Harold V. Childs has moved from Mo- Phone: Ryon 18171 torola Communications and Electronics, Inc., to Ampex Corporation where he will 536 S. Fair Oaks, Pasadena 1, Calif. be manager of the field service engineering department . Jerome H. Levy and Robert Winston have been appointed vice - presidents of National Musitime Corp., ,ubsidiary of Audio & Video Products Corp., New York. Levy will be general manager and Winston will be in charge of FOR THE ADVANCED AUDIOPHILE, "EVERYTHING IN HIGH FIDELITY" sales . Al Stroka has been named industrial sales engineer for Pentron Corpo- LIVINGSTON HAS DEVELOPED A From Primary Components ration; in addition to serving as field SUPERBLY ENGINEERED, UNIQUELY to Completed Custom Audio Equipment engineer, he will cooperate with manufac- DESIGNED. LOW COST BINAURAL turers in designing industrial electronic devices ... PLAY -BACK UNIT. /UST LOOK AT THESE PLAYBACK FEATURES: KIE F Vacancy created on the executive staff of Daystrom, Inc., by appointment of Flutter G Wow: Negligible Sound Corp. Robert Erickson to presidency of The Hum Level: 60 db Down Heath Company, a Daystrom subsidiary, Output: 5 millivolts 820 West Olympic Blvd. Los Angeles 15, Calif. will be filled by Walter W. Slocum who Frequency Response: ± 2 db 20- 15,000 cps has been named assistant to Thomas Roy At 7i/2 ips Richmond 7 -0271 ZEnith 0271 Jones, president of the parent company Selector Switch: Binaural; Monaural; Half Cramer Yarbrough has been named Track (You can play standard half track, sales manager of American Microphone or binaural tapes) Company, Pasadena, Calif. . . . Arthur Attractively housed in a blonde or ma- Priest, audio consultant, has joined Reco- hogany finished cabinet as shown: CANADA ton Corporation as sales manager of the High Fidelity Equipment cartridge division ... Daniel R. von Reck- NET $119.50 linghausen has been promoted from senior only: $99.50 Complete Lines Complete Service project engineer to chief research engi- Chassis Ht -Fl Records Components neer of Hermon Hosmer Scott, Inc., Cam- and Accessorlon- bridge, Mass. Bi -Fi Recorded Tapes &LECTRO-UO10E from the Livingston Library SOUND SYSTEMS 9.dsa.fny Notaa... Net $10.00 ea. 141 RUNDAS ST. Wi9T. TORONTO, CANADA. Special recognition for excellence in Superbly recorded music by the leading packaging design and sales promotion domestic and foreign combos, orches- techniques for magnetic recording tape was given to ORRadlo Industries, Inc., tras and choral groups, adds a new di- manufacturers of IRISH brand tape, in mension to yo'ur listening pleasure . . . SPLICES MAGNETIC TAPE the April issue of Modern Packaging magazine. ORRadlo was spotlighted in a # 701 Schubert- Unfinished Symphony Neatly - Ocickly - Easily BN Sibelius -Finlandia feature article as a leader in "sales -appeal Mussorgsky on Bald nil a.dd.e whin saner., to recorder or weer. packaging #703 -Night Mountain platt spit, aimed at a new multitude of BN taaM. gsNermss supply of taw spicing tabs. handy tide. home users." Borodin-Polovtsian Dances precut "Attractive packaging, point - Sibelius Triste Mebuction. and daatk case. Only $1.50 po.tpald. 11 your dsalor of -sale displays, and self -selling displays -Valse can't supply you. order born have played a big role in increasing sales of IRISH magnetic tape 82 per cent dur- COUSINO, INC. ing the pest year.' according to Nat 2SS7 Medleew Aw T. 1. OW Welch, ORRadlo sales manager. Elgin National Watch Company has become one of the nation's largest manufac- tirers of high -precision electric relays IF YOU ARE MOVING with the purchase of Advance Electric h 'Tlay Co., Burbank, Calif. Formal transfer Please notify our Circulation Department of ownership took place April 30. It was the 91- year -old watch company's third #709 Music, Wine, and Candlelight -Vol. I at least 5 weeks in advance. The Post move into the fast -growing West Coast BN (by Austria's leading Schrammel Office does not forward magazines sent electronic industry, group) earlier purchases in- #AT7 Rampart Street Ramblers to wrong destinations unless you eluding Neomatic, Inc., and the American pay ad- Microphone Company. Amount of the pur- 56N (Wilber de Paris) ditional postage, and we can NOT dupli- chase prit-e was not stated. Complete listings of Binaural, Dual, and cate copies sent to you once. To save Triad Transformer Corp., Venice, Calif., Single track recordings on request. Write yourself, us, and the Post Office a head- gave recognition to 61 of its 384 employees Dept. BN ache, won't you please cooperate? When at a dinner held recently. Awards for five years of service were given to 52 em- notifying us, please give your old ad- ployees while nine received awards for dress and your address. EONARD **ow. INC. new having been with the company ten years. Ov Ce0107. N N- Y.., y. N.Y CawMMr 7.0515 In presenting the awards, O. D. Perry, Circulation Department vice -president, said that nearly six million Mail and phone orders filled, dollars had been paid In salaries since the 25% deposit, Balance C. O. D. RADIO MAGAZINES, INC. company's inception in 1944, and that the company had shipped more than six thou- New! 160 page, 1956 Audio Reference P. 0. Box 629 Mineola N. Y. sand tons of finished transformers to elec- Guide Available soon. . Enter your trical and electronic firms throughout the name on our mailing list now! country.

AUDIO JUNE, 1955 79

www.americanradiohistory.com Full A.F. range! ADVERTISING -lowest distortion INDEX TAKE

Acro Products Co. 73 Allied Radio Corp. 61 Altec Lansing Corporation 7 TIME Ampex Corporation Cover 2 Audak Co. 45 Audiogersh Corporation 53 Audio League Report 67

Belden Mfg. Co. Cover 3 OUT Bell Telephone Laboratories 14 Inc. 56 A p.p. nut put iransfurnur specially designed for really David Bogen Co., high qua'ity A.F. reproducing equipment. Power up to British Industries Corporation facing p. I. 26. 27, 30, 34, 35, SO watts at 60 a /a. Each hal p ' ry ill brought out to 36, 37, 42, 44, 45, 50, 71 terminals se separate winding and tapped at 43"0 of 6 tune. Considerable N.F.B. ran be taken from the rerond- Brush Electronics Company an and fed to a point three or four stages bark. For specifications and priers of Partridge Transformer Carter Motor Co. 2 and name of local distributor write to: Centralab, Division of Globe -Union 75 Partridge Transformers Ltd. Classified Ads 78 Sales Co. Inc. e/o British Electronic Collaro Record Changers 55 23.113 45111 Bond, Long Island City, I. N.V. Cousino, Inc. 79 ALSO AVAILABLE Williamson specifi- TYPE WWFB Built to the fatuous Electro -Sonic Laboratories, Inc. 46 cation and available in a .ride range of impedances. Electro- Voice, Inc. I, 13 Power rating 16 watts cotton emus steady lone $27.75 Net. Electro -Voice Sound Systems 79 TYPE C.F.B. Leads the Cray . 'C' Core Technique. Power up to 60 watts from 22 c/s to 30 Kr /s. Dis- tortion less than P' with no N.Y.B. $43.75 Net. Fairchild Recording Equipment Corp. 48, 59 Fenton Company 40 P A R T R I D G E TRANSFORMERS LTD. Goodmans Industries, Ltd. 77

TOLWORTH SURREY 'ENGLAND Harvey Radio Co., Inc. 65 Heath Co. 63 High Fidelity House 79 Hollywood Electronics 79 Hughes Research and Development Laboratories 5 Hycor Co., Inc. 10 BOUND VOLUMES Karlson Associates, Inc. 77 Cancer strikes 1 in every 4 Kierulff Sound Corporation 79 Kingdom Products, Ltd. 41 Americans. It strikes with 1954 ISSUES AUDIO MAGAZINE vicious swiftness. Too often it 79 Leonard Radio, Inc. is discovered - too late.

Marantz. S. B. 75 To protect yourself and your now available 69 McIntosh Laboratory, Inc. family, have a thorough Minnesota Mining and Mfg. Co 9 medical examination every National Company 11 single year without fail. Six months after such an exam- Partridge Transformers, Ltd. 80 ination, every woman over $10.00 each postpaid. Peerless Electrical Products 68 Pickering G Company, Inc. 31 35 should return for a pelvic Pilot Radio Corp. 78 checkup. Every man over 45 U. S. Delivery only. Presto Recording Corporation 39 Professional Directory 79 should have a chest X -ray twice each year. Many can- 66 Radio Shack Corporation cers can be conquered if Rauland -Borg Corporation 72 Send order Rek -O -Kut Company 32 caught in time!

and remittance today. Schober Organ Corporation 70 Scott, H. H.. Inc. 47 STRIKE BACK AT CANCER.. Sonotone Corporation 51 MAN'S CRUELEST ENEMY

Technical Tape Corporation 3 Tetrad 43 Give to Box CF -4. Triad Transformer Corp. 4 AMERICAN AUDIO United Audio Products 49 United Transformer Co. Cover 4 CANCER SOCIETY P. O. Box 629, Mineola, N. Y. Weathers Industries, Inc. 54

i 'III6 l' IIII I Illi b!IIIiIIL', I','a lui l';III iJl IIIII

80 AUDIO JUNE, 1955

www.americanradiohistory.com WIRE AND CABLE FOR EVERY ELECTRONIC PRODUCT

WIREMAKER FOR INDUSTRY SINCE 1902 BELDEN MANUFACTURING CO. CHICAGO 2 -8

www.americanradiohistory.com LEADERS IN MINIATURIZED MINIATURIZATION FOR OVER TRANSFORMER TWENTY YEARS...

COMPONENTS 50 ra "" Items below and 650 others in our catalog A. HERMETIC SUB -MINIATURE AUDIO UNITS COMPACT HERMETIC These are the smallest hermetic audios made. AUDIO FILTERS Dimensions . . 1/2 x 11 /16 x 29/32... Weight.8 oz. 111 TYPICAL ITEMS UTC standardized filters are for MIL Pri. Imp. Sec. Imp. OC hi Max. level Type low pass, high pass, and band No. Application Type Ohms Ohms Pri MA ±2 db (Cye.) dbm V N -30 Input to grid TF1A10YY 50 62,500 0 150-10,000 +13 pass application in both Inter- N -31 Single plate to single TF1A15YY 10,000 90,000 0 300-10,000 +13 grid, 3:1 stage and line impedance de- H -32 Single plate to line TF1A13YY 10,000 200 3 300 -10,000 +13 signs. Thirty four stock values, H -33 Single plate to low TF1A13YY 30,000 50 1 300-10,000 +15 impedance others to order. Case 1-3/16 x H -34 Single plate to low TF1A13YY 100,000 60 .5 300-10,000 + 6 impedance 1 -11/16 x 1.5/8 -2.1/2 high DC, 50 Henries -1 Ma. DC, 4,400 ohms. 11-05 Reactor TF1A2OYY 100 Henries -0 ... Weight 6-9 oz. H -38 Transistor Interstage TFIA15YY 25,000 1,000 .5 300-10,000 +10

'Car be used with higher source impedances, with corresponding reduction in frequency range and current

'1/4111 SUB -SUBOUNCER HERMETIC MINIATURE AUDIO UNITS HI -Q TOROIDS UTC Subouncer and sub - subouncer units provide ex- MQE units provide high Q, excellent stability and ceptional efficiency and frequency range in miniature relia- minimum hum pickup in a case only. 1/2 x size. Constructional details assure maximum bility. SSO units are 7/16 x 3/4 x 43/64 ... Weight 1 -1/16 x 17/32 . . weight 1.5 oz. 1/50 lb. TYPICAL ITEMS MA D.C. Type Application Level Pri. Imp. in Pri. Sec. Imp. Pri. Res. Sec. Res. Type No. Inductance DC Max. ISO.1 Input + 4 V.U. 200 0 250,000 13.5 3700 MQE1 7 mhy 135 50 62,500 MQE -3 20 mhy. 80 roo MIIMI7oomm SSO-2 Interstage /3:1 + 4 V.U. 10,000 0 -25 90,000 750 3250 MOE 5 50 mhy. 50 Ilil11111l SSO.3 Plate to Line +20 V.U. 10,000 3 200 2600 35 MQE.7 100 mhy. 35 w ItltII.I 25,000 1.5 500 MQE -10 .4 hy. 17 1_iSI SSO-4 Output +20 V.U. 30,000 1.0 50 2875 4.6 MOE -12 .9 hy. 12 20 SSO-5 Reactor 50 NY at 1 mil. D.C. 4400 ohms D.C. Res. 4700 3.3 M MQE-15 2.8 hy. 7.2 O , s o n 20 25 30 n 40 SSO-8 Output +20 V.U. 100,000 .5 60 SSO.7 Transistor +10 V.U. 20,000 .5 800 850 Interstage 30,000 .5 1,200 125 Impedance ratio is fixed, 1250:1 for SSO- 1,1:50 for SSO-3. Any impedance between the values shown may be employed. OUNCER (WIDE RANGE) r AUDIO UNITS HERMETIC e rs i _IIM VARIABLE i Standard for the industry for 15 yrs., these rs 1_IE% units provide 30- 20,000 cycle response in a INDUCTORS s 1_Iillie_e1=1

case 7 8 dia. x 1 -3/16 high. Weight 1 oz. 1/_!sI/\ These inductors pro- 1`..M_ M TYPICAL ITEMS vide high Q from 50 - 10,000 IIMI NS MOM cycles with exceptional stability. Wide in- Type I= 111211111 ductance range (10 - 1) in an extremely >o CO No. Application Pri. Imp Sec. Imp retarocnc.cres,...r.rto compact case 25/32 x 1-1/8 x 1 -3/16 0.1 Mike, pickup or line to 50,200/250, 50,000 ... 1 grid 500/600 Weight 2 oz. 2. 0.4 Single plate to 1 grid 15,000 60,000 TYPICAL ITEMS 2s to 2 grids, 15,000 95,000 0-7 Single plate TYPE No. Min. Hys. Mean Hys. Max. Hys. DC Ma D.C. in Pri. NYC -1 .002 .006 .02 100 0-9 Single plate to line, D.C. 15,000 50,200/250,500,600 in Pri. NVC -3 .011 .040 .11 40

0-10 Push pull plates to line 30,000 ohms 50, 200/250, 500/600 HVC-5 .07 .25 . .7 20 plate to plate NVC -6 .2 .6 2 15 0.12 Mixing and matching 50,200/250 50,200/250,500/600 Hvc -10 7.0 25 70 37g 0.13 Reactor, 300 Hys. -no D.C.; 50 Hys. -3 MA. D.C., 6000 ohms HVC -12 50 150 500 1.5 unan rwrASC AT xooctics UNITED TRANSFORMER CO. LET US MINIATURIZE YOUR GEAR. 150 Vorick Street, New York 13, N. Y. EXPORT DIVISION: 13 E. 40th St., New York 16, N. Y. CABLES: SEND DETAILS OF YOUR NEEDS for SIZES and PRICES "ARLAB"