VACUUM TUBE VALLEY'· Published Quarterly Celebrating the Hisfory cnd Quality of Vacuum Tube Technology Issue 4 Volume , Price S8.00 Spring/Summer 1996 Happy 60m Birmday to the 6L6 The history and test results of this legendary audio power rube Page 3 GE, RCA and Sy/vflllia 6L6GCs Hanllon-Kardo1l Citation 1I In This Isslte... Editor's Page 2 6L6 Forever: History and Tests 3 VTVListens to 6L6 Types J I Wby 88 to 108 FM? 12 HKCitation I and 11 15 Classic Vacuum Tube Manuals 6L6 Cutaway vrv GE, RCA, Citation 0Modificarum 22 reviews Sylvania, Tung-Sol Vintage Bookshelf Speakers and other tIIb.:: manuals by era and An examina tion and listening evaluation of mbc manufacturer rage 26 Designingfor Sound 23 the most popular home hi-fi bookshelf loud­ speakers from 1955-1972 Page 28 Ntws 25 Tube Industry Early FM Broadcasting A Banle of the FM Bands between [he beau­ Review of Tube Mamtals 26 roerars, broadca5ters, and manufacrurers in rhe 1940s Page 12 Vintage BookshelfSpeakers 28 Vacuum Tube Valley is published quarterly for electronic enthusiasts interested in the Audio Test Be,uIJAC Meters 33 colorfvl post, presentond future vacuum01 tube electronics. Wri".n and Produced in !h. Un;",d.. 51" of ArneriCl E D TOR' S P AGE Technology dcparunem. John will ((<IIeh the annual subscription rale only 28%. vrv Control Grid this class starting this fall. John is also For subscribers in the US, the fatC is on his second session of a class entided S32.00/yr-four issues, for Canada by Cbarlie Kittleson, Editor "Audio from Tubes� al the Randall 540.00/yr and for Asia, Europe and the Museum in San Francisco. In this dOlSS. rest of the World S4;.00/yr. Please send atlcndees listen and learn why woes gel payment in cash. US Money order, per­ the music right. They also learn about sonal check (VS only), or bank check a Turn Friend on to Tu bes tube elecnonics by building an excellent drawn on a US bank with magnetic Have any of you ever lent a [uhe tube Stereo amp step-br-stcp in the class!! encoding. "' lifier ro a friend who is new (0 tubes :r an find that you couldn't gel it back? All Maga�ine of Japan recendy pub­ Don'l miss OUI! Be sure to renew your Most music lovers who he:lr tubes for lished a detailed anicle by John Atwood .ubscription to VTV. We have some' thc first time in their own home become on a single-ended amplifier he designed great articles coming up next year includ­ hooked and transistor audio never satis­ that can use a \':lriery of octal based pen­ ing: KT88/6550 hiSTory and tem, 6DJ8 fies them again. I have given Stereo 70s todes or triodes. hisrory and tests, Theremin construction project, Fisher 500 receiver hisrory, and Scan illlegrated tube amps to friend� Safety First! and relatives as gifts and they continue to Vintage Tuner Shoot-Out number 2, sv- rave about how much they love them. It When working on any type of vacu­ 811 wbe amp construction projects, doesn't take a mcgabuck high-end system um tube equipment, remember that tubc� Audio Test Bench Series, vrvinterviews to make good music. If you have a friend run on high vohages Ihat can and will kill with audio pioneers and more! who you think might enjoy his/her music you! Please exercise caulion when work­ ing with tube circuits by de-energizing Credit Cards in VTV FUlUre through tubes, lend them your spare tube anlplifier or preamp for a week or £wo. before work, wear shoes to insulate you Due ro a significant demand from our from ground, and ncver poke around a subscribers, VIV will begin accept in You may not get il back right away, bur ! you may have converted another to our Jive circuit with a screwdriver or other credit cards for subscriptions, renewa s, ranks. conductive tool. VTV assumes no liabili­ books and other products beginning July ry for injury from readers working on 15, 1996. This will allow foreign sub­ VTV in th e News t�be equipmenr mentioned in this maga­ scribers ro sal"e moncy and hassle and We have had a nUlllber of rC<jue:.ts to ztne. hopefully increase our overseas subscriber reprint recent articles from VIV. One of base. We will be able to accept VISA, vrv Subscription Increase them includes Mark IV Audio Corp. in Master Card and American Express. JUSt Buchanan, Michigan who obtained per­ It is official; VTV, due to a 1;0% send us your name, card number, bank mission 10 reprint my article on the Altec increase in size (from 16 to 40 pages) and expir�ltion date for fast service. 604 coaxial loudspeaker story from VIV plus the added postal expense has raised We Need a Few Good Articles #3. Mark IV owns Altec-Lansing Corporation and used the article for a Here is your chance to get published. recent sound contractors trade show and v-rv is always seeking quality articles for marketing purposes. AClDC from our readers; in particular, audio and Mag:rune of Taiwan, ROC asked permis­ I'acuum tube historical perspectives, sion to reprint Eric's 300B article (fans­ broadcasting hisrory, early recording Stu­ lOlled to Chinese. dio equipment, early theatCT sound sys­ tems, microphones, speaker and equip­ John Arwood, our Technical EditOr, ment manufacturer profiles and more. has been busy [hese days. Besides being We will also consider do-it-yourself or President of the Northern California technical articles on your audio, radio or Tube Enthusiast Group, John has been electronics construction projects relating teaching classes on tube amplifiers!! to vacuum tubes. Authors whose articles Cogswell College in Sunnyvale has added get published will receive payment, the a college level class on tube amplifier the­ amount depending on the length, ory in their Musical Engineering research involved and graphics. EDITORIAL STAFF '" Copyrig,t 1996 Vacuum Tube Valley Vacuum Tube Valleyis published quarterly 'M and Big Tone All righb re�. e for el droni c enlhusiasts interested in Ihe Charles Kittleson - Editor and Publisher No port of Ihis ptJhlication may be reprinted Of colorful past, present and fuhJre af vacuum Tec ca otherwisereproduced hJbe electronics. John Atwood - hni l Editor without written pemtission of thepubli�r. Eric Barbour - Associote Editor Subscription is US$32.00/yeor 14 issues} Send circ ulatioo and editorial $40/Canodo and $45/A�ia and Europe Dove Wolze - Audio Consultant correspondence to: CASH, US BANK CHECK, CREDIT CARDS Vacuum Tube Valley Steve Porr - ArtDirector 1095 E. Duane Ave., Suite 106 To subscri be, renew or change address coli Julie p, Wemer- CopyEditor Sunnyva1e, CA 94086 USA or FAX us at (408)733-6146. [email protected] VACUUM TUBE VALLEY • 6 L 6 FOR EVER 6L6 Forever 1936-96 60 Years ofAmplifier Service By Eric Barbour If you ever find yoursdfbeing harassed by techics who insist upon criti­ ci'ling you for your interest in vacuum tubes, there is an casy answer. They can be silenced with a simple <juestion. Ask them if any early type integrated circuits will still be manufactured and used in new products in, say, the year 2030. If they're honest, the answer will be "non. Then tell them that the first-ever beam power tube is still selling in the millions TOday, and shows no sign of becoming obsolete..... after 60 years. That should get rid of them. As ofMarch ! 996, the mighty 6L6 is celebrating its 60th birthday. It's still being manufactured in Russia and China. And its popularity in guitar amps is assured for the wnceivable future. Various "expens� in the rnainstream elec­ tronics industry, who relentlessly kill old technologies and curse people who use them, can do nothing about the 6L6 � it continues to be a dominant voicemaker of rock'n'roll guitar. Many Uexperts" have (fied to simulate Cutawayof the 6L6 guitar amp with various semicon­ 6L6 Beam ductOr-laden gizmos, from complex ana­ StrucNlreby log computers to OSP chips, with varying Ke1llLeech technical success, and with linle or no financial success. There are numerous companies making 6L6 powered amps today. Fender, Mesa-Boogie, Ampeg, Peavey, Kendrick, Victoria, Soldano, THD, Louis Electric and many others have staked some of their product lines on the 6L6. So don't accept the muttering ... about "dead technology. " NOW you can get full I. History 60W.tt, from 0 poir of 6L6's In 1931, rhe audio outputS of radio sets were dominated by [riodes such as the UX-171 and UX-245. But even [hough push-pull 245s could produce 5 waHS easily, there was ongoing pressure from manufacturers for ever-more­ efficient OutpUt tubes. The pentode was the answer at firs!. It originated in Europe, with the first American power types being the Champion P-704 and Arcturus PZ. These were very early types and had some reliability problems. They were quickly superseded by ReA's UX- Ellriy 6L6 Amp VACUUM TUB E VALLEY 6 L 6 FOREVER RCA 1614 IlIId6L6melnl wbes 247. rdeascd June !931. Suddenly you could get 2.5 watts out of a single [Ube, with easy drive requiremencs and al only 6L6GX (Isolallliu bti#) alld6L6G 250 volts! Millions of radios used thl'; '47, and its descendant, the 42 with its 6.3 volt heau,'r, was even more popular. The 38, 48, 59, 2AS, and 6F6 followed, as did European types such as the Mama AOPen, Cossor MP/Pen, Osram MPT4, Mullard PenA4 and numerous olhers. BUI RCA engineers were pursuing more: lofty goals: low distonion with high efficiency.