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August, 1961 50, for High -Fidelity Audio Output

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August, 1961 50, for High -Fidelity Audio Output AUGUST, 1961 50, FOR HIGH -FIDELITY AUDIO OUTPUT NEW RCA -7868 NOVAR POWER PENTODE OFFERS OUTSTANDING DESIGN ADVANTAGES With this new tube RCA brings all the advantages of novar Wider spacing between pins (0.172 ") -to minimize the possibility design to high- fidelity circuitry. of voltage breakdown; hence greater reliability. RCA -7868 is a high -perveance 9 -pin novar power pentode Pin length of 0.335" -for for output stages of hi -fi audio amplifiers, phonographs and firm retention of tube in socket. radio receivers. You'll get up to 44 watts of power output Pin circle diameter of 0.687" -large enough to permit use of both from a pair of them in Class ABA push -pull service in audio T9 and T12 envelopes. amplifiers. RCA Dark Heater -found exclusively in RCA receiving tubes... RCA -7868 is the first hi -fi tube type in RCA's new novar additional assurance of reliability. line of large, all -glass 9 -pin receiving tubes. Its cost to you is less than that of any equivalent tube regardless of base RCA 7868 has two base -pin connections each for grids #1 and 2; configuration. special radiator on siderods of grid #2 assures cooler operation. RCA -7868 has all the advantages of novar design, the only Take full advantage of this major contribution all -glass, integral -base receiving tube design to audio to offer: technology. See your RCA Field Representative for full de- Larger internal lead diameter -for strong cage support and high tails... or write: Commercial Engineering, Section thermal conductivity for very effective heat dissipation. RCA Electron Tube Division, Harrison, N. J. ¡IA Hie Most "Trusted Name in Electronic RCA ELECTRON TUBE Vair DIVISION FIELD OFFICES EAST: 744 Broad Street, Newark 2, New Jersey. HUmbcidt 5 -3900 MIDWEST: Suite 1154, Mercha -dise Mart Plaza, 3hicago 54, lllincis, Whitehall 4 -2900 WEST: 6801 E. Washington Blvd., Los Angeles 22, California, RAymond 3 -8361 2 AUGUST, 1961 Vol. 45, No. 8 Successor toD9. Est. 1911 C. G. McPROUD Editor and Publisher SHERWOOD-- DAVID SASLAW Managing Editor AUDIO THE JANET M. DURGIN AIM Production Manager FIRST 11LNRY A. SCHOBER Representatives Contributing Editors FM Business Manager Bill Pattis & Associates, EDWARD TATNALL CANBY 4761 West Tauhy Ave., L. CAHN GIOVANELLI SANFORD Lincolnwood 46, Ill. JOSEPH STEREO Advertising Director HAROLD LAWRENCE James C. Galloway, CHARLES A. ROBERTSON EDGAR E. NEWMAN 6535 Wilshire Blvd., MULTIPLEX SANTON Circulation Director Los Angeles 48, Calif . CHESTER RECEIVER AUDIO Articles FM- Stereo: Time- Division Approach 20 Carl G. Eigers Product Detector for FM- Stereo 23 F. L. Mergner Filters For FM- Stereo 26 Norman H. Crowhurst FM- Stereo Adapter 78 Daniel R. von Recklinghausen Schematic of H. H. Scott the S8UUU AUDIO Reviews 64 0tts 299° Light Listening 8 Chester Santon for Record Revue 66 Edward Tatnall Canby only those who want the ultimate ... Jazz and All That 74 Charles A. Robertson AUDIO in General Audioclinic 2 Joseph Giovanelli Letters 6 Audio ETC 12 Edward Tatnall Canby Editor's Review 18 About Music 80 Harold Lawrence At last, Stereo Multiplex is here ... This Month's Cover 103 and, once again, Sherwood is first ... ready immediately with a brilliant Advertising Index 104 combination of Sherwood's "high rated" FM tuner design plus all circuitry necessary to receive the new FCC -approved FM multiplex stereo... two 32 -watt amplifiers, two phono /tape PRODUCT PREVIEW SECTION 36 pre -amplifiers and all controls necessary for playing records, tape or Amplifiers and preamplifiers 36 Pickup arms 86 TV. The S -8000 Receiver needs only the addition of speakers to complete a Headphones 105 Phono pickups 88 basic system for FM stereo listening and enclosures Tape Recorders 90 enjoyment. Overall size, just 16 x 4 x 14 Loudspeakers .50 inches deep. Microphones 95 Tuners 44 Sherwood's dramatic Correlaire Furniture Modules are the perfect Miscellaneous 106 Turntables and record changers 82 setting for your Sherwood hi fi components. Choose from sixteen interchangeable modules, styled with a MFMgFg contemporary flair in hand -rubbed ..o,..n e. Walnut and Pecan woods. Have truly AUDIO (title registered U. 8. Pat. OR.) L publLhed monthly by Radio Maga- flexible room arrangements. A beautiful Y/1\G: zines. Inc., Henry A. Sehober, President; C. O. McProud, Secretary. Executive four -color brochure is yours for the rates-U. 8.. and Editorial Mips, 204 !Pont St., Mineola, N. T. Subscription asking. Sherwood Electronic Possessions, Canada. and Mexico, $4.00 for one year, $7.00 for two years: all Z Laboratories, Inc., 4300 N. California other countries $5 00 per year. Bingle copier 50 *. Printed in U.B.A. at 10 18, ea DkCovern Ave., Lancaster, Pa. All rights reserved. Rothe contents copyrighted Ave., Chicago Illinois. .INC' 1961 by Radio Magazines. Inc. Second Clan poetad paid at Lancaster. Pa. For Complete Technical Details Write Dept. 8A RADIO MAGAZINES, INC., P. O. Box 629, MINEOLA, N. Y. Postmaster: Send Form 3579 to AUDIO, P. O. Box 629, Mineola, N. Y. AUDIO AUGUST, 1961 1 CON-CO - MINIM\ I - /FA fI1 AUDIOclinic t. :\' J JOSEPH GIOVANELLI` Dear Reader - with the added advantage that the cable I really must congratulate you. You is still balanced. have been very good about enclosing If you prefer the 72 -ohm line, you must stamped, self -addresed envelopes with use a matching transformer at the an- your letters. This helps me to get answers tenna and another one at the receiver in back to you in the shortest possible time. order that the required 300 -ohm im- You see, I answer all letters, even when pedance will be met at both places. (Such your question is used in "Audioolinic." transformers are available from your local Record stereo... If I did not follow this procedure, some parts jobber.) of you would wait a long time for your Moving the antenna as far from the play stereo... answers because of the delay between the street as possible will sometimes reduce with the new receipt of a letter and the publication ignition noise in the tuner. date of the material in that letter. It tray even be necessary to use an an- 4'oncord model MI I note, too, an increasing interest in my tenna cut exactly to the frequency you other column, "Audio Techniques." I have most wish to hear in order to obtain max- Why settle for a tape player when you can quite a number of suggestions and they imum gain at this dial setting. will make reading, believe. own a Concord 401 stereo tape recorder for interesting I know Newcomers to AUDIO probably don't R. F. Interference in Home Music Systems no more cost. With the 401 you can record about this feature which appears inter- a library of 25 one hour stereo tapes for mittently. The purpose of "Audio Tech- Q. I have constructed an integrated less than $50.00 compared with the cost niques" is to allow readers who have stereo amplifier -preamplifier. I ara experi- encing some trouble, however, in that, of over $300.00 for the equivalent in pre- found short -cuts in building electronic equipment, have developed unusual test with the amplifier operating, I get an recorded music. procedures, or ideas which can make ex- interfering station in the background. Am I correct in assuming that I have a The Concord 401 stereo tape recorder perimentation with electronics a little easier, can share their ideas with other ground loop or a tuned circuit somewhere offers superb in sound quality an advanced readers. Send any such information to me in the hookup? The intereference exists design precision instrument. The 401 con- at the address shown; many others will with no input to, or after, the preampli- tains both stereo record and playback pre- profit from your knowledge. J. G. fier stage. By switching to only one pre- amplifiers. amplifier and feeding through both Records stereo anywhere, plays is Ignition Noise Reduction amplifiers, I still get it. My question through any high fidelity system. how shall I trace this down and eliminate Q. I use an AM -FM tuner. I live on a the trouble? William H. Ross, Dearborn, Features: 4 -track stereo and monaural busy street and I get a lot of ignition Michigan. recording, sound on sound recording, two noise when listening to FM. The station A. This question is really one which VU meters, individual channel controls, I listen to is about .90 miles away. I use deserves an entire article. All I can 10 electrimatic remote control. Mounts verti- a TV antenna, a yogi with a rotor, which here is to point out some of the places I direct towards the station. Is there any cally or horizontally -ideal for custom in- which are likely to cause interference and modification I can make in the tuner to you have do best to trace the stallations. Frequency response, 30- will to your stop ignition noise? If I use 72 -ohm coax- particular cause associated with your 16,000 cycles 2 DB at 71/2 IPS. Flutter ial lead -in, how can I make an impedance equipment. and wow, less than .18 %. match to the 300 -ohm balanced input on Oxidation is a major cause of interfer- my tuner? William T. Cramer, Stockton, ence. Such oxidation can occur in switch Price including custom carrying case California. contacts, tube socket contacts, and poor $249.50. A. There is no internal modification soldering connections. These latter which can help the tuner to reduce the troubles are especially common in ground Write Today: Send for Concord's booklet noise output when the signals are too leads. Oxidation can also occur at the "401 -All the Facts" regarding the quality weak to saturate the limiters.
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