www.americanradiohistory.com the big PLUS FOUR ,111.1111 in tubes for hi-fi! "low noise and low hum" characterize the performance of this From pre -amplifier to power amplifier, mono high -mu twin RCA -7025... triode-ideal for your pre -amplifier designs. or stereo, you can design a comprehensive line of "versatility" high-fidelity products around these 4 RCA keynotes the applications for this tube-a sharp - tube types. And your designs with RCA cutoff pentode and a medium -mu triode in tubes one envelope-for add up to recognition RCA -7199... low-level stages. ... for quality, perform- ance, prestige. Contact your RCA Field Repre- "compact, but powerful" can describe monophonic and stereo- sentative for details. For technical data, write phonic power amplifiers designed around this 9 -pin miniature RCA Commercial Engineering, Section RCA -6973... -a pair in Class AB1 can deliver up to 20 watts output. K -91 -DE, Harrison, N. J. "power deluxe"-up to 76 watts with only 2% distortion from a pair in Class AB1 audio service-new structure design pro- 744 Broad St.. Newark 2, New Jersey. HUmboldt 5-3900 RCA -7027-A vides exceptional electrical stability and reliability. MIDWEST. ANOTHER WAY RCA SERVES YOU THROUGH ELECTRONICS Suite1154, Merchandise Mart Plaza, Chicago 54, III., WHitehall 4-2900 RADIO CORPORATION OF AMERICA WEST: Tube 6355 East Washington Boulevard. Los Electron Division Harrison, N. J. Angeles 22, Calif.. RAymond 3-8361 www.americanradiohistory.com NOVEMBER, 1959 VOL. 43, No. 11 Successor to RADIO, Est. 1917. Model S-5000, 20 -f -20W Stereo Dual Amplifier-f189.50 a Model S-3000II, FM Tuner-$105.50 a.w.mr=.... ._ rR .,,,,,.... ,....., AU Io Model S-4400, Stereo Preemp.+36W Amp.-$159.50 ENGINEERING MUSIC SOUND REPRODUCTION C. G. McProud, Editor and Publisher Henry A. Schober, Business Manager 4550 Harrie K. Richardson, Associate Editor Linda Sueskind, Assistant Editor Janet M. Durgin, Production Manager Edgar E. Newman, Circulation Director Model 5-1000 II, 34W Monaural Amplifier -5109.50 w w .. Sanford L. Cahn, Advertising Director The "complete matching home music center" MEMRER Midwest Representative- -monophonic or stereophonic. or ( MAHO W. A. Cook and Associates Again another year -recommended by one of >n 161 East Grand Ave., Chicago 11, 111. the most respected and authoritative Re- CW West Coast Representative- search Testing Organizations as embodying .pC more numerous, more advanced engineering James C. Galloway "firsts"-more inherent quality for trouble - . tNC e 0 5 6535 Wilshire Boulevard, Los Angeles 48, Calif. free operation-more real value for every dollar than many competitive products sell- ing for more. PLUS: Features that in their CONTENTS unsurpassed engineering win the most dis- criminating audio -hobbyist; but also features I; if, reio-Ili 2 that in their simplicity and ease of opera- Letters 6 tion appeal to everyone-housewife, audio - A udioman of the AConti] 12 novice, or just plain music lover. Cabinetry of quiet that A udio ETC-Edward Tetuan Canby 14 elegance blends with any decor. Editor's Review And Sherwood, unmatched at any price, is 16 Fair Trade priced for your assurance that once Universal Stereo Control Center-Francis A. Gicca 19 you have bought Sherwood, you didn't in Calculation Chart for Vented Cabinets-Victor Brociner 22 a better "deal" someplace else. ' Puzzled About Amplifiers '1-Norman H. Orowhurst 24 is only for those who want the Defense and the Hi-Fi Bachelors-C. H. Malm.stedt-Part II 29 For further details write: Sher Tape Guide-Tape Recorder Accessories-Herourti, Burstein 32 tronic Laboratories, Inc., 4300 N A Figure of Merit for Output Tubes-Robert M.. Mitchell 40 Avenue, Chicago 18, Ill. Visual Stereo Monitoring-Burwell Graham and George L. Foster 45 Series -Tuned Push -Pull Oscillator-E. J. Cuddy 48 Transistorized Microphone Presinip-Horace E. West 50 most honored of them ail= Speaker System for Perfectionists-James A. Mitchell 52 Equipment Profile-H. H. Scott 299 and 222 stereo amplifiers-Koss Stereo- phone headset-Fisher X -101A stereo amplifier 59 Record Revue-Edward Tatnall Canby 66 SHE RVOOD Jazz and All That-Charles A. Robertson 70 New Products 82 New Literature 84 About Music-Harold Lawrence 86 Coming Hi-Fi Shows _ ....... _ ___ _ .____-_... 87 Advertising Index 108 COVER PHOTO-The Forecast Music Sphere, latest in Aluminum Company of America's continuing series of designs in aluminum for tomorrow. This unit, created by industrial designer Lester Beall, was on display at the recent New York High Fidelity Show. The components installed in the Sphere are : Pickering Gyropoise 800 Stereotable, 196 Unipoise arm, and 371 Stereo-Fluxvalve, Gronunes 209 preamp-control unit, Dynakit Stereo 70 amplifier, and Jensen Galaxy II speaker system. The dual -coil woofer is in the lower half of the hemisphere with the two satellite tweeters on the "outriggers." AUDIO (title registered U. S. Pat. Olt.) Is published monthly by Radio Magazines, Inc., Henry A. Schober, President; C. O. McProud, Secretary. Executive and Editorial Offices. 204 Front St., Mineola. N. Y. Subscription rates--C. S. Poserions. Canada and Mexico. $4.00 for one year. $7.00 for two years. all other countries. $5.00 per year. Single copies 50g. Printed In C.S.A. at Lancaster. Pa. All rights reserved. Entire contents copyrighted 1959 by Radio Magazines. Inc. Entered as Second Class Matter February 9, 1950 at the Post Office. Lancaster. Pa. under the act of March 3, 1879. RADIO MAGAZINES, INC., P. O. Box 629, MINEOLA, N. Y. Postmaster: Send Form 3579 to AUDIO, P. O. Box 629, Mineola, N. Y. FOR COMPLETE SPECIFICATIONS WRITE DEFT AUDIO NOVEMBER, 1959 1 www.americanradiohistory.com AUDI_clinic r.....r.. -e 1 JOSEPH GIOVANELLI ,.. ,_ A I ,Sc ,,,k,..... Stereo Adaptor resi-l:uice compared to that of the at- tenuator, and place it in series with the ,..., My problem concerns mom , r.sion to Q. hot side of the stereo. I have the following midipnient: attenuator. The potentiom- a eter sections should Fisher 80-R AM -FM tuner, an Rico HFT90 be wired as rheostats. (The reason you Íl,0 FM tuner, a Fisher 80-C audio control, a cannot use a potentiom- eter to do the is 60 -watt McIntosh power amplifier, a Scott entire job that ganged po- tentiometers which track uniformly FOR EVERYONE 2100 preamplifier, a Ferrograph tape re- be- tween gangs are difficult obtain.) corder, and two speaker systems. I know to Of ...perhaps for you course, the that I could build a stereo adapter which attenuator sections will not track unless all resistors making up would suffice to mate my equipment if cer- the at- tenuator are 1 -per -cent units. The tain questions were answered. These are use of the questions: the series potentiometer may be justified in two ways: 1. How can I design a single volume (A) Although this potentiom- is placed in control for both channels after they have eter series with the load, thereby causing the load to see different been balanced using the controls on the impedances Scott 210C and the Fisher preamplifier? with different control settings, the effect will be negligible since the 2. Where do I tap off the signal total resistance from of the pot the Scott and the Fisher, and into what section is small compared to that kind and resistor, and of the total into which the load works. (B) There will be some so on do I lead it? error in tracking be- tween the two sections of the 3. Next-how do I feed the signal back potentiometer because the total resistance of the to what place in the Scott and McIntosh? potenti- ometer is small compared to that of the at- 4. Monophonic playback I'm not worried tenuator. The amount of tracking error about since the McIntosh will do nicely cannot be severe enough to without help. However, nowhere have I cause sufficient unbalance between channels to be detected Tandlwry n how you can parallel two dissimilar aurally, and that is the only kind of -SPEED, 4 -TRACK amplifiers. John A. Timm, Boston, Mass. de- 3 tection which really matters. I RECORDER A. 1. The problem of adjusting the vol- STEREO It should have been stated ume of both channels with one potentio- that the total PLAYBACK resistance of the potentiometer should meter is a difficult matter. The best solu- be The Tandberg 5 is not everyman's figured in such a way tion is the use of a two -deck step switch that it can give a tape recorder. It is an instrument of 3 made up as an attenuator. The maximum total variation perhaps db when built to incredibly rigid standards of placed in series number of switch positions you can find with the attenuator. perfection, designed to provide the 2. There will probably be 24. This will mean that are two ways of tapping the discriminating listener with a life- signal: (A) The easiest is simply to feed you must design your attenuator in 3 or time of listening pleasure. To the the output of each preamplifier into the educated car, the difference be- 3.5 db steps. With such an arrangement there may be times where might desire series combination of attenuator and po- tween Tandberg reproduction and you tentiometer, having a volume control setting somewhere the output of each preampli- conventional recorder playback is fier going between these positions. This can be done to its respective gang. The arm immediately apparent. of the by using a potentiometer having a fairly attenuator would be connected to Yet, the difference is subtle. It is re- the input of its appropriate power ampli- flected in shadings and nuances that * 3420 Newkirk Ave., Brooklyn 3, N.