Audio-1960-Aug.Pdf
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.A \EW LOW- \OISE TWIN TRIODE to improve performance and simplify the design of Audio Pre- Amplifier Stages Low noise, high performance, moderate cost - provided by the new RCA -6EU7, a high -mu, nine- pin miniature twin triode designed especially for high -gain, resistance- coupled, audio pre -amplifier stages -in high fidelity amplifiers (monaural or stereo), amplifier kits, tape recorders, juke boxes, and public address systems. Noise and hum are minimized by the use of double - wound, helical heaters, and a new base layout which keeps heater leads well away from the grid leads. Low microphonism, high mechanical strength, and reli- ability are assured by a short, rugged cage which provides sturdy support for the tube electrodes. New base arrangement also simplifies stereo layouts. The accom- panying diagram shows how the basing arrangement facili- tates the design of an amplifier using the two triode units for isolated stereo channels. For technical information, contact the RCA Sales Repre- sentative at our office nearest you, or write directly to RCA Electron Tube Division, Commercial Engineering, Section H 91-DE. Harrison, New Jersey. EAST: 744 Broad Street, Newark 2, N. J. HUmboldt 5-3900. MID-WEST: Suite 1154, Merchandise Mart Plaza, Chicago 54, III. WHitehall 4-2900. WEST: 6355 E. Washington Blvd., Los Angeles 22, Cal. RAymond 3 -8361. The Most Trusted Name in Electronics RADIO CORPORATION OF AMERICA AUGUST, 1960 VOL. 44, No. 8 Successor to RADIO, Est. 1917. only for those who want the ultimate "TOP RATED" AU D Io again and again ENGINEERING MUSIC SOUND REPRODUCTION -and NOW AGAIN! C. G. McProud, Editor and Publisher Henry A. Schober, Business Manager Janet M. Durgin, Production Manager °0.4 083®. Edgar E. Newman, Circulation Director _' - ,,,r,,, Model S -5000. 20 +20 wett "slam" Dual Amplifier- Preamplifier. Fair Trade Price -5189.50 Sanford L. Cahn, Advertising Director MEMRgn Midwest Representative et - 1MANG W. A. Cook and Associates 230 East Ohio Street, Chicago 11, 111. Model 5.2200, FM -AM -MX Stereo tuner, tnn Fair Trade Peke -5119.50 ' West Coast Representative +s i: - eeeast lames C. Galloway y1NCea 6535 Wilshire Boulevard, Los Angeles 48, Calif. CONTENTS Audioclinic- Joseph Giovanelli 2 Letters 6 Light Listening- Chester Santon 8 Audio ETC- Edward Tatnall Canby 10 AMERICAN Editor's Review Microphone 16 AUDIO INSTITUTE Calibration -Dan Peters - 19 n LAS'IOh Sr r,n.Oa. N, 1.02 Cubic Feet and 45 cps. Richard Sequerra 20 Start with Mono-Build up to Stereo -C. F. Barton 22 BUYERS' GUIDE SECTION October n. 1959 Amplifiers and Preamplifiers 23 Tuners Sherwood Electronic labs.. Ina. 27 4300 North California ATORO. Loudspeakers Chicago 18. Illinois and Enclosures 41 Record Changers 50 Gentlemen, Turntables We find that the incorporation 52 of a enter-channel output and Pickup Arms a damping factor selector to 56 July. 1959. increases the Phono Pickups 58 Summary Rating of the Sherwood Tape Recorders S -5000 to he highest of all 89 18 Stereo Amplifiers tested to Tape Accessories 92 the All Evaluation Test Report.. Microphones Sincerely. 92 Miscellaneous AMERICAN AUDIO INSTINTE Electronic 93 Organ Kit 95 Tape Guide -Equalization -Herman Burstein 28 Felts R Sr.., Record Revue- Edward Tatnall Canby 80 Executive Director Jazz and All That -Charles A. Robertson 66 The "Most honored of them all" About Music-Harold Lawrence 78 AUDIOMAN S -5000 stereo amplifier- preampli -. No. 11-Tames S. Swinehart 88 fier is Advertising Index 96 joined by the S-2200 stereo COVER PHOTO-Living room stereo demonstration in the display of British tuner. As with its "Top Rated" Industries Corporation at the recent British Exhibition U.S.A. during June. The predecessors, the S -2200 features visitor entered the complete display at the lower right comer of the photo, climbed FM "Interchannel Hush" plus push a few steps and proceeded along the raised passage seen at the left. While listening button selector, internal plug -in to properly reproduced stereo music from the equipment on display, he could ob- adaptor for Stereo FM Multiplex, serve a lucid description of each element of a home system as detailed on easy -to- 2 "Acro- beam" tuning indicators, read placards with suitable illustrations. As he passed out of the living -room simulcast FM /AM stereo. All area, he saw a display of the non -hi -fl products imported by British Industries Sherwood tuners feature Corporation. The equipment used in the display consisted FM sen- of a Garrard 88 sitivity below microvolts changer, Leak tuner and Leak amplifier installed in a River Edge chairside 0.95 and table, 1/2% distortion @ 100% with two Wharfedale speakers opposite. The entire display was designed by Rex FM. Frey of Lord & Taylor, New York. For further details write: Sherwood AUDIO (title registered U.S. Pat. O0.) is published monthly by Radio Electronic Laboratories, Inc., Magazines, Inc.. Henry A. Srhober, President; C. C. 4300 McProud, Secretary. Executive and Editorial Offices, 204 Front St., Mineola, N. Y. Subscription rates Possessions, Canada, and Mexico, - U. S. N. California Avenue, Chicago 18, $4.00 for one year, $7.00 for two years, all other countries, $5.00 per year Single Copley 504. Printed In U.S.A. at 10 McGovern Ave., Lancaster. Pa. All rights reserved. Entire contents copyrighted 1950 by Radio Illinois. Magazines. Inc. Second Class pottage paid at Lancaster, Pa. RADIO MAGAZINES, INC., P. O. Box 629, MINEOLA, N. Y. Postmaster: Send Form 3579 to AUDIO, P. O. Box 629, Mineola, N. Y. For Comprete epecITlcetlons write Dept. A -M. AUDIO AUGUST, 1960 1 for the finest in high fidelity kits AGROSOUND AUD I 0 clinic << These popular Acrosound kits are simple and fast to assemble ... bring the newest sound advance- ments into your home in a matter of hours! Best of all, Acrosound's easy - to- build, reasonably priced kits save you dollars! JOSEPH GIOVANELLI' Grounding a Home Music System 3. Since hum and its causes are some- times quite complicated, the problem of Q. (The following is a composite answer grounding any type of home music system ACRO'S PREAMPLIFIER to two letters written on two different to a waterpipe or radiator depends on the A new all feedback preamplifier with low dates by the same reader. Each of these amount of hum and upon the nature of the noise, 2 MV referred to phono input, high letters, of course, received a personal hum. If the system runs perfectly well, do gain, 60 DB phono and tape, and low distor- reply.) nothing at all about such grounding. I tion, 0.15% IM for 1.5V out. Extra features Letter 1 -I am putting my equipment cannot say just how far to go with ground- Include individual bass and treble controls, into a cabinet in which I will have to cut ing the entire system to waterpipes and rumble and filters, switch, third scratch phase several holes in the back for power leads, the like since sometimes this will aggravate channel output, light matrix, and exclusive audio leads, etc. To snake it neater, I have Mic. Dub switch. Supplied with two low noise a hum condition rather than relieve it. If 7199 pentode /triode, two 7247 dual triode taken a Bud Minibox and arranged it for any of the equipment you plan to use is tubes. $09.50 Factory Wired $114.50 several power outlets. I have also taken of the a.e: d.c. variety, do not ground it or another Bud Minibox and used other types any associated components to a radiator. of sockets for audio connnections and an- Failure to observe this precaution is almost tenna leads. My problem is that in using certain to cause a blown fuse and damage standard phono connectors I have used to your equipment. two wires, one from the center pin and one from the ground lug. Is there any danger of a ground loop because of the "Putter," Flutter and Tracking Force fact that the two phono connectors are connected on the ground side through the Q. My main problem is as follows: I metal box itself? have an odd difficulty in the turntable. Letter 2-I have now converted my sys- There are two objectionable sounds. One is tem to stereo. I would now like to know that it has apparently more flutter in pitch what is the proper and complete way to at the center of records, as compared to ACRO'S ULTRA LINEAR II AMPLIFIER ground the entire system and how it should the edge (this one really is strange, as This famous 60 watt basic amplifier has long be grounded to the 117 -volt outlet box or flutter should be uniform if the turntable been a favorite of discriminating audiophiles. causes it) and it has an odd, "puttering" Acro perfected Ultra-Linear circuitry has been waterpipe ground. When lift the tonearm to place it on sound for a small part of a revolution on combined with a unique feedback system to I sounds as if it shakes the an record, get a hum until I remove my many records. It provide amplifier with unusually low dis- a I much tortion, superior feedback stability, and finest finger from the arm. Should the tonearm record a little. This "puttering" is transient performance. Construction time is be grounded to the turntable? Will this worse at a cold start, reducing to a much only two hours. Supplied with two EL -34 out- get rid of the hum which occurs when less noticeable amount after the motor put tubes, one 12AX7, one 12ÁU7, and GZ34 the tonearm is touched? warms up. It is much worse near the center rectifier.. $79.50 Factory Wired $109.50 I certainly would appreciate any help of the records.