...mie sue:eaeora.f.yi re aóou/6údiey ./ www.americanradiohistory.comAmericanRadioHistory.Com NEW RCA -7868 NOVAR POWER PENTODE OFFERS OUTSTANDING DESIGN ADVANTAGES With this new tube RCA brings all the advantages of novar Wider spacing b: tween pins (0.172 ") -to minimize the possibility design to high -fidelity circuitry. of voltage break I own; hence greater reliability. RCA -7868 is a high -perveance 9 -pin novar power pentode Pin length of O. 35" -for firm retention of tube in socket. for output stages of hi -fi audio amplifiers, phonographs and radio receivers. You'll get up to 44 watts of power output Pin circle diame r of 0.687" -large enough to permit use of both from a pair of them in Class AB1 push -pull service in audio T9 and T12 env lopes. amplifiers. RCA Dark Heat r -found exclusively in RCA receiving tubes... RCA -7868 is the first hi -fi tube type in RCA's new novar additional assur. ce 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 t o base -pin connections each for grids #1 and 2; configuration. special radiator .n siderods of grid #2 assures cooler operation. RCA -7868 has all the advantages of novar design, the only Take full ad antage of this major contribution to audio all- glass, integral -base receiving tube design to offer: technology. Se: your RCA Field Representative for full de- Larger internal lead diameter-for strong cage support and high tails...or write: Commercial Engineering, Section K- 91 -DE, thermal conductivity for very effective heat dissipation. RCA Electron ube Division, Harrison, N. J. The Most Trusted Name in Electronics RCA ELECTRON TUBE DIVISION FIELD OFFICES EAST: 744 Broad Street, Newark 2, New Jersey, HUmboldt 5 -3900 MID EST: Suite 1154. Merchandise Mart Plaza, Chicago 54, Illinois, WHitehall 4 -2900 WEST: 6801 E. Washington Blvd., L s Angeles 22, California, RAymond 3 -8361 www.americanradiohistory.comAmericanRadioHistory.Com AF1tFR, 1961 Vol. 45, No. 11 Successor to Rà9 , Est. 1911 C. G. McPROUD Editor and Publisher SHERWOOD, DAVID SASLAW U D Io Managing Editor only for those who want the ultimate in JANET M. DURGIN FM Production Manager Stereo Broadcast Reception HENRY A. SCHOBER Representatives Contributing Editors Business Manager Bill Pattis & Associates, and EDWARD TATNALL CANBY 4761 West Touhy Ave., SANFORD L. CAHN JOSEPH GIOVANELLI Stereo Record Reproduction Advertising Director Lincolnwood 46,111. James C. Galloway, HAROLD LAWRENCE EDGAR E. NEWMAN 6535 Wilshire Blvd., CHARLES A. ROBERTSON Circulation Director Los Angeles 48, Calif. CHESTER SANTON AUDIO Articles S -8000 FM /MX 64 Watt Stereo Receiver 16 % " x 4" x 14" deep. $299.50 Common -Bass Sterco Speaker System 79 Francih F. Chen Stereo -Plus- Center To Two Recording Channels 28 Harold Reed The Electronic Organ -A High Fidelity Musical Instrument 35 David Wolkov S- 300014 FM/ MX Stereo Tuner x 4" x IOW, deep. Low -Cost Stereo Conversion for Studio 14" $160.00 Console 44 C. G. McProud "Sineward" Distortion in High- Fidelity Amplifiers 52 John W. Campbell, Jr. Ravinia Model SR3 3 -way 26' x 15" x 131' deep. S -5000 If 80 Walt Stereo Amplifie, Speaker System $139.50 AUDIO Reviews 14" x 4" x 121/2" deep. $199.50 Light Listening 8 Chester Santon Record Revue 68 Edward Tatnall Canby Correlaire Walnut i, Fl Furniture Jazz and All That 74 Charles A. Robertson AUDIO Profiles Empire "Troubador" Turntable System 62 Model 398 Norelco Tape Recorder 62 Continental "200" University Speaker System 64 Classic Mark II Fairchild Compander 66 Model 510 AUDIO in General Audioclinic 2 Joseph Giovanelli Letters 6 Audio ETC 12 Edward Tatnall Canby With FM Stereo broadcasting (multiplex) an Editor's Review 16 established reality, Sherwood proudly offers every component you need for superb stereo Tape Guide 32 Herman Burstein reception. Sherwood stereo amplifiers and New Literature 81 tuners are pre- eminent in the field, and now -in the S -8000 Receiver -the ultimate in New Products 82 compact reception quality is achieved. The About Music Harold Lawrence exciting new Ravinia Model SR3 3- speaker 86 system features extremely low intermodula- This Month's Cover 87 tion distortion and unusually flat frequency response. Industry Notes 97 Cabinet is hand -rubbed walnut. The perfect setting for hi fi components is Advertising Index 98 Sherwood's Correlaire contemporary furniture modules hand MEMBER -in -rubbed Walnut and Pecan. ,.rr11.,r >, Sherwood Electronic Laboratories, Inc., 4300 AUDIO (title registered U. S. Pat. Off. ) is published monthly by Radio Maga- N. California Ave., Chicago 18, Illinois. -r sines, Inc., Henry A. Schober, President; C. G. McProud, Secretary. Executive ti and Editorial Offices, 204 Front St., Mineola, N. Y. Subscription rates -U. S., 0 For complete technical details, Possessions, Canada, and Mexico, $4.00 for one year, $7.00 for two years; all o write Dept. 11A. other countries $5.00 per year. Single copia 50e. Printed in U.S.A. at 10 o McGovern Ave., Lancaster, Pa. All rights reserved. Entire contente copyrighted euLlt 1961 by Radio Magazines, Inc. Second Class postage 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. AUDIO NOVEMBER, 1961 1 www.americanradiohistory.comAmericanRadioHistory.Com Wide -Band Ribbon Microphones SMOOTHEST FOR RESPONSE STEREO PRECISE Il AND FIGURE 8 MONO PATTERN FOR PRO- JOSEPH GIOVANELLI FESSIONAL actually AND HOME Poor Phono Equalization To determine the input load ,vwwwwasagi presented to the pickup you need only to USE Q. I recently built a speaker system. connect an ohmmeter across the input to When connected with my amplifier and the phono position of the preamplifier FM tuner, it sounds fine with nice, clean with the cartridge disconnected. The re- lows. I recently bought a turntable and sistance measured at this point will rep- SPACER STEREO cartridge. I paralleled the two channels of resent the load seen by the cartridge. It for consistently the cartridge by means of a "Y" adapter should be adjusted as is required by the and feed this into the magnetic phono jack superior stereo characteristics of the high- frequency re- on the back of my 122-watt preamp ifier- recordings sponse. amplifier co nmbination. When playing ono - More likely, however, you may possibly phonic discs, the low notes appear o be have connected the two outputs of your Complete Data attenuated. I have played only one s ereo- pickup out of phase. Suggest you cheek Available phonic disc (monophonically) so fa and this first. cannot compare the low notes on it to hose COMING! heard when 'using my tuner at this ime. Determining Speaker Resonance A NEW STEREO The recommended load impedance dif my MICROPHONE Q. wish to a bass reflex enclosure, cartridge is 47,000 ohms per channel. When I build but do not know the resonant frequency I parallel these, I get 23,500 ohms. I do I not know the load impedance of the nput of my woofer. The speaker has a nominal impedance of 8 ohms. Richard Teperson, DYNACO of the phono positition on my am lifer combination. Is there some 'mismatch that Cincinnati, Ohio. Super I don't know about or am I just imagining A. Every musical note has an audio the loss of lows? frequency, or pitch. If you have good Fidelity If you suggest paralleling the i puts musical pitch, or if you have a piano with some value of resistance, woul you handy, you can tap the speaker cone and -' OUTPUT state the valve and also the watta e of note the tone which was produced. You can the resistor? Since I don't know th im- then figure the frequency of the tone using TRANSFORMERS pedance at the input of the phono raph standard reference pitches and the proper position of the unit, can you sugg t to ratios between musical notes. I shall be me a way of measuring it? Charles M. Mc- glad to explain this further if requested. Advanced pulse techniques and Dy- keough, Philadelphia, Pennsylvania. If the foregoing procedure is impossible naco's patented para- coupled windings for you to use, you will have to run an and massive grain- oriented cores insure A. is you First of all, it possible that impedance curve of the speaker. To do this, superior cquare wave performance and are lacking low frequencies because the near -perfect transients. All transform- an audio oscillator is connected across a discs used for the comparison simply in series network consisting of a variable ers handle full rated power from 20 themselves lack lows. Otherwise, there is resistor (0 to 100 ohms) and the speaker cps to 20 KC, and are conservatively no reason why the paralleling of the cart- rated and guaranteed to handle double to be measured. Feed in various frequen- ridge sections should result in a to s of nominal power from 30 cps to 15 KC. cies and adjust the value of the variable low- frequency response. the r com- If resistor so that the voltage across the re- SPECIFICATIONS mended load impedance presented t the Response: Plus or minus 1 db 6 cps to 60 KC. sistor will equal that of the voltage across Power Curve: Within 1 db 20 cps to 20 KC. cartridge was not observed, there ould the speaker. Do this for each frequency Square Wave Response: No ringing or dis- be a change in the amount of high fre- 20 cps. to 20 KC. fed into the speaker. Then, measure the re- tortion from of the Permissible Feedback: 30 db.