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Big ... Big Sound!

300 Watts of Badass Bass

Great Tube Sound on a Budget

Restoration of an A.tee 287W

I'll'. EDITOR.S P AGE AND INDUSTRY NEW S

El Nino washed OUl the vimage elec­ vrvIn The News - Again! tronics flea market on Saturday, a crowd As a result of our Tube Enthusiast's VTV Issue # 9 of almost 500 new and familiar tube enthusiasts showed up or our tube Weekend, most of the editors were Table of Contents: f vrv trade show and display show. We also interviewed by the Sa" Frallcisco presented Tube School III with John ChTOllic'� newspaper for a major article Anvood, vrvTech Editor, as class that appeared in rhe February 7, 1998 Legacy of the 50 Watter•..... 3 leader and Evan Aurand wilh Terry Business Section. VI"V's "lech Ediror, Buddingh handling rhe Amp John Anvood, was pictured on the front TransmittingTube Test Amp •• 7 School. page of the article .

o : Business Week Mag'J.zine also gOt into Dumpster: 2CS 1/5670...... 1 0 New York Tube Sch ol FaJl1998 the act and was interested in the �tube If we get at least 50 pre-regis[(�red listening to SE 211/8455 .... 11 audio� phenomenon. They interviewed sign-ups (by 8/15/98), will present vrv yours truly and lOok a picture of me sit­ Practical Tube Audio School in the ting in the'.VTV test lab. The final arti­ Ampeg SVT History••••••••••••• 13 New York area during September or cle was three pages in the subscriber edi­ October 1998. This is an intensive tion of the March 30 issue. The Firs. Tube PCs ••••••••••••••• 18 eight hour class covering the basics of tube electronics, tube amp circuit th eo­ for Articles caU Winter 1998 CES Report ..... 21 ry, tube testing and grading, repair & VTV is always seeking quality articles troubleshooting techniques, equipment on audio and electronics histor y, good Vintage Audio in Japan •..•.. 22 mods & upgrades and listening tesrs. sounding mbe hi-fi projects, pro-audio Tubr School is d�signrdfor attrndm at history a d related subjens. We accept Analyzers ••••••••25 rhl' bl'gimll:r to imum�diau kv�' ofskifL n 11 articles only in simple text format on will also present a four hour vrv 3-112 inch floppies. Any photos should Altec 287W Giant Amp••••••• 28 Guitar Amp School in the afternoon, be clear and sharp. Schematics should again, if there are at least 30 sign-ups. be clearly drawn with all component Bargain Tube Hi-Fi•••••••••••••• 30 John Atwaod, MSE£ and vrv values listed. We do pay authors for their work if it is pu lished in VI\/, Metallic ...... 32 Technical Editor, is Tube School class b leader. John has over 20 years experi­ Share your knowledge and passion ence in vacuum mbe amp design and about tubes with the world communiry Advertiser Section ••••••••••••••35 of tube enthusiasts-wrire for repair. Additional speakers will include; vrv. Pugliesi, The Fisher Docror; Charles Al vrv Subscription Price Increase Kittleson, vrv Editor and other nOta­ Tube School Update bles in the field of tube electronics. Due to increased rents, postage and has presented twO Tube Schools priming COSts, vrv is raising the sub­ vrv The cost for Tube School is $149 pre­ since last November. We presented scription COSt and per-issue COSt of the paid (before August 15, 1998) and Tube School 11 in Tempe, Ariwna wilh maga7.ine . Current issue news scand and $179 at the door. Price includes all the assistance of Antique Electronic diStribulOr COSt is $9.00/issuc, US sub­ class marerials in a binder plus coffee Supply. For the first time we included a scription Tate is now $36/yr-four issues, and tea in the AM. To guarantee that four hour presentation on guitar ampli­ $43/Canada, $56/Europe and $66 Asia this event will occur, please send or FAX fiers taught by Evan Aurand. In addi­ and world. This price increase is effec­ us your name, address, tele hone num­ tion, Ritchie Fle gler, of Marketing p tive with #9. i VP ber, whether you want the hi -fi or guitar vrv for Fender Musical Instruments, gave a amp class and credit card information to Changes in VIV ralk on the state of tube guitar amps at #9 reserve your seat in class. IfW� d() flOt Fender Musical Instruments. Due to space constraints Part 2 of the gn the rl'quirl'd numbtr ofciass sign lipS Bruce Moore interview and the 572-3 byAll ust 15, 1998, YOUT paymmt wiii be In February, VTV sponsored the first g push-pull project will nOt be annual Bay Area Tube Enthusiast's rl'fimded promptly. in this issue. They will be in vrv #10. Weekend. Even though the rains of

EDI'FORrAL STAFF Volley is publi h d quarter­ Copyright 1998 s e Vacuum Tube Valley'" ond Big Tone'to ly for electronic enthusiosts interested in the Charles Kittleson • Edi r and Publisher of this publicotion may ep i colorful past, present ond of vacuum to No port be r r nted future or otherwi!>e reproduced without written tube electronics. . ohn Technical Editor of the pvbli�her. J Atwood permi�sion Subscription US$36.00/year (4 issuesl Eric Borbour -Staff Edi or Send t circulation and editorial $43/Canoda and $66/Asia, $56 Europe to: Terry Buddingh . Guitar Editor correspondence Cosh, Bonk Check, or Credit Cords Vacuum Tube Valley us Sieve Parr - Art Director are accepted for payment 1095 E. Duone Ave., Suite 106 Julie P. Werner - Copy Editor Sunnyvale, CA 94086 USA phone - (650) 654 • 2065 e·mail @vocuumtube.com FAX • (650) 654 • 2065 Website . www.vocuumtube.com # 1095-4805 155N

VACUUM TUBE VALLEY ISSUE 9 • LEGACY THE WATTER o F 5 0

Not many other types were so widely "p;,d,nd mod;fi,d. A,m"",;ng ofm- L egacy 0 f Ih e 5 0 Wa IIer: sians include the 203H for medical diathermy, with plate and grid caps; 303A

P was the United Electronics version; ', Tarlor's T-125 was a 150w version with 211 & 845 __ mu of20 and plate and grid caps; laylar's By Eric Barbour 303C/HD203A had a piate cap and mu G fi of25;29 5A was the Western Elec[fic ver- 4AZ ©��1��9�8�A�I9 �I �R�; g�h:"�R:"�':�:.d::: sion from 19 33: T-203Z was a Taylor ver- __ � sion with mu of 85; and there were coo I large transmitting cubes in mass produc- lntro ____,-:-_ ____--======-:-_� many other versions from other firms to I- rion. The plain- tungsten 203 , was also " liH here. This helped cement the 4-pin As usual, we have a Story for you that made under various proprietary numbers, jumbo base as a major industry standard doesn't unfold in a rational way. Once , such as PG 132 again, a tube family in common use today and HWI5. sprang from a line of industrial triodes, and became audio gold by sheer accident Unlike most and random chance. other power rubes of thc era, History it was equipped It begins with an experimental triode with a standard from 1917. General Electric had devel­ base for easy oped the "Type U PliotTon" for use in change-out; . Navy radio transmitters; it was called CG- preVIOUS power 1144 when it was PUt into radios aboard triodes were seaplanes during World War I. After the usually mount­ war, the Type U became the UV-203. ed on framcs Introduced in March 1921 by RCA and and attached to made by GE, for use in AM radio rrans­ theiT circuits mittc�Ts, it had a mu of25 and a pure with flying tungsten filament.In short, it was primi­ leads. This large tive. Yet the 203 was one of the earliest bayonet-lock base with 4

in the very early days of radio broadcast­ stubby pins, originally ing. Note: WE's203 series of tubes were developed by Western much smaller than industry-standard203 Electric and often called rypes and not compatible. the �jtlmbo," became a standard for power tri­ Eventually this led to the2 I 1. It was odcs. developed by Western Electric from their experimental series G, with the first ver­ Thorium was a big sion21 1Acompleted in late 1921 , then improvement. The UV- copied in lare 1923 by Westinghouse, and 203A, introduced in marketed by them and by RCA. With a June 1923 by RCA and mu of 12.5, it was intended for RF dielec­ Westin house, was one g tric hearing and audio modulators. A dull of the first powcr mbes and pedestrian tube for dull everyday to be introduced with a jobs. (If a radio engineer of the 1920s moriated filament. Its lived to sec what old 21 Is are selling for dissipation, rated at today, he would probably die laughing.) lOOW, made it popular. 21 1 rypes were widely made by otber Later it was doned by firms, as they caught on in mundane Amperex, Deforest, GE, industrial and medical applications. Sylvania and Taylor. 1921 RG4

VACUUM TUB E VALLEY ISSUE 9 LEGACY THE 5 0 WATTER o F

with a plate cap; 211 H was Amperex ver­ sion with a plate cap; United made a 311 series (311CH with plate cap), mainly for RF heating; RCA's 835 of 1937 was a Iow-capacitance version for the Iow end of the VHF band; and RCA's 838 was a variabIe-high-mu version for zero-hias Class B use. (That's right, it has a vari­ able-mu grid, making it high in distor­ tion in SE connection.) And all those VT-4Cs made by GE from 1938 to 1945 for aircraft transmitters, which became common and cheap surplus after the war.

This led to RCA's 805 and WE's 331A, which had v-ariablehigh-mu grids and were intended fot Class B AF modulators. It also led to 810 types and to a long series ofTayJor types: T-125, T-155, T- 200, 814, and 822, plus many, many variations and special-duty types.

The last development was the 845, believed to have entered development by RCA in 1927 and not released until 1931 as the UVB45. In an eta when transmit­ ting (fiodes wete headed toward high-mu W'E211D, WE2fJEandWE276A design and grounded-grid or Class B operation, the UV84S was an aberration: We stern Electric's versions starred with Some other versions of the 21 1 include a 75-watt power triode with a mu of 4.8. rhe 211A ; the211B, C and D werejusr the We stern Electric 242A, llsed in WE's Latet it was up-rated to 100 wans. the same rube with different grades of fil· model BOA audio amp; 242B and C were Ridiculously archaic and difficult to amenr. The 211E was nOTOrious for its aimed directly at audio equipment, espe­ drive, by 1945 it was obsolete except for use in the WE 43A [hearer amplifier. A cially the C, which found use in the 0- its continued use in older RCA BTA­ pair of small nichrome-wire 90684 broadcast moniror amp; the WE series transmitters as the audio modu\aror were installed in lhe filament circuit, 2GIA was used in early WE AM trans­ final amp, in a Class A push-pull pair. inside the aecua] tube, to hdp stabilize it mitters, while rhe WE 27GA was a IOOw­ Such transmitters were often pressed into at high frequencies. This makes old dissipation version; 214A, 0 and E wen.' service after World War n by small local 211Es highly collectible. 211As without grids, for use as rectifiers; broadcasters, many carrying "race� music RCA's 217C from 1926 was like a 214£ and programming. Millions of Americans

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Enrly nnd illfer 21ls RCA 845 CETRON 845 &

VACUUM TUB E VALLEY ISSUE 9 • LEGACY OF THE 50 WATTER

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VACUUM TUBE VALLEY ISSUE 9 • LEGACY o F THE 5 0 WATTER

use in AM broadcast To day modulators. There were other manufac­ Simply compiling a list of all the firms turer's designations that made 2115 in the past 70 years for the 845, would be an impossible undertaking; although it did not 211s were aSToundingly popular before enjoy nearly as much 1950, then nearly became museum popularity or vari­ pieces. In spite of the wide manufacture ability as the 203 or of 50-waner tubes in their variegated. 211. Its mu was toO forms, in the 21 st century wc arc down to tWO manufacturers: a Chinese factory, low to make it suit­ able for RF-he:ning and Richardson Electronics in Illinois. power oscillators, The Beijing uSino� factory produces and any continued generic clones of the later GE 211/VT- 4C and the late RCA 845, both with manufacture was JUSt to keep p e-1950 graphite plates and aluminum-sheU bases. r Richardson makes an 845, allegedly on AM transmitrers retubed. the original RCA tooling, in small quan­ tities and selling for a high price under High mu was the the Cenon label. Manufacture of later overwhelming trend relatives, such as the 80S and 810, con­ afrer The war, and tinues in China and at Richardson. grounded-grid RF wcce the Although the Utrue" 50-waner types last frontier for glass have been reduced to two specialt), manu­ triodes--power facturers serving the high-cnd audio mar­ retrodes and pen- ket, there is a similar tube from Russia: the Ulyanov GM-70. Its basing is unique ______todes elbowed them and its mu is about 7, yet in many L����""��",Jjt'\C�� -,,- J out of mOST other were exposed [0 R&B and gospel music applications. The worm turned in the respects it is amazingly similar to the 211. via the smooth sounds of ush-pulJ 845s, 19805, and the last laugh is on the high- This triode, made since the 19405, is lit­ driven by interstage transro ormers, wit h no mu f amily. For although rhe 811A, 5728, de-known outside of the Russian elec­ negative feedback. AlICC, RCA and WE 3-500Z and orhcr high-mu types contin- tronics industry. also used the 845 in a few (heater amps ue to be popular in RF applications, the during the 1930s and 1940s.. large, crude 845 has become nearly a relj· Ourro Western Electric's 284 series was very gious objeCT to neurotic audiophiles, So, it appears that the 50-waner is similar to the 845 and enjoyed lengthy especially in Asia. showing new life and continued manufac­ ture into the 21St century. In spite of its sheer impracticality, the obsessive and demanding audiophile market continues to maintain its availability, and probably at prices that would shock our fathers. Remember, as recently as the early 1970s one could buy a WWII surplus Vr-4C for as little as $4. Bibliography I. 70 Years of Ra dio Tubes and Valves, John Stokes (Vestal Press, Vestal, NY, third edition, 1992), pp. 127-132.

2. TransmittingTube Catalogand Guide, TaylorTubes, Inc., 1937.

3. Tube Lore, Ludwell Sibley, Flemington NJ, 1997.

4. Saga of The Vac uum Tube, Gerald F. J. Tyne (Howard W. Sams Publishing Co, Indianapolis IN, 1977), p. 151, ISO, 287, 288.

Many thanh to Lau,m Pt!(ltham ofthe Antiqu( Wir&JJAMciarion, Aljones ofthe 7ransmitting Tube MIIJ(um, and Brothrr Par Dowdfor their inva/uabk assistanu with the historical background.

VACUUM TUB E VALLEY ISSUE 9 TRANSMIT TIN G TUB E T ES T A M P

The driver circuit is only mcanr for dri­ ving !llbes in negative-grid region (no A Transmitting Tube the grid I;urrent). This is the most I;ommon mode for medium and low mu triode OUt­ Test Amp put tubes. By adding a snong Qthodc follower. say a rriode-connected EL34 or 6550, positive grid operation (class of Al) By John Atwood © 1998 All Rights Reserved the output tube is possible, opening up Ihe amp for use with high-mu tubes such as the 838, 811A, and SVsn-160.

Running the 6B4G filament on DC is essential, since AC I;auses inrolerable hum. Te sting the audio performancc of power lated filament supply, with its voltage DC A simple solid-Slate supply with I;hoke fil­ [Ubes with plare volrages higher than 500 adjusted by Varial;. The driver a desk-top [ering is uscd. The 0.6 ohm power resistor volts becomes more complex rhan simply stage: and bias supply were moumed on was picked to give 6.3 volts DC at the fil­ dropping the tubes into a conventional the main board. ament. The high voltage needed for the amplifier - mainly because there are few amplifiers available for these tubes. A simple driver using an old penrode Tr ansmitting tubes also come with a vari­ and a filamelltary rriode without feedback cry of socket and filamem voltagcs. gives a good low-impedanl;e drive with types To help us evaluate uansmitting tubes, a decent frequen/;)' response and distortion. single-channel (mono) test breadboard The 6J7 may look unfamiliar to was built with a large degree: of Aexibiliry tube purists, but the older low-transoon­ in audio testing 211-dass transmitting ductance rypes an sound very good. The tubes. In addition to being a good Mtest_ 6B4G allows a low 10K plale resistor wilh bed," it turns Out that wirh good tubes high plate voltage while producing low and , it sounds quite good, distortion. To insure good voltage swing, a and could be the basis for a high-qualiry 600 vol! power supply is used. This may single-ended power amp. seem high compared to rhe 325 volt maxi­ mum rating, but kee:p in mind that in a QtUT/ON: TIle amplifier deJeTibed in rransformer-I;oupled amplifier, which this this articu is inundeJto be rued Dill, rating was meant for, the plate an have driver stage is obtained by using a stan­ for testing rompollents, alld has deadl, voltage peaks twice the B+ supply. Used as dard radio-type power transformer run­ high-voltagepoints exposed!If you wall! a rc:sisranl;e-coupled amplifier, the 6B4G ning into a vohage doubler. The 6AX4GT to use the cirr,lit for gelleralpllrpose lis­ runs conservatively in this application. damper tube rectifiers give a nice slow tening, it "eeds to be p4rkaged so tiJ4t While initially designed for driving JUSt turn-on. The GAX4GT is abundantly nilhigh-voltllge po;ms 4rl s4fely the 211-rype !llbcs, Ihe driver has enough available in North America as a surplus t/lclosed! head-room so that it o.n drive 845s. The tube. regulated bias is nOI enough for the low TV Test Amp Design mu of 8455. bur simply pulling he OD3 t The high volrage for the output tubes is out of its socket allowed the bias to rise Iking a Mone_ofF" design, the 211 lest run through a 0-100 mA meter mounted high enough for our amp was built around componems on ICStS. in an old sloping "meter" box. Also in the hand. Key to the amp is a good, high­ quality high volt-age power supply. A Fluke 3010 precision high volrage supply had recemly been picked up at a ham radio swap. hs maximum ratings are 1011 volts and 500 mA. h would have been bener go U o 1250 volts (the to t maximum rating 0t the 211 and 845), but 1000 volts was still reasonable. Since both the OUtpUt tube and output transformer would have to be easily changed, a wood­ en bread-board consuuction was used, wilh high-voltagc:s enclosed where possi­ ble. Three tube sockets were: ever installed, al;commodating the jumbo four-pin 211- • rypcs (203, 211, 838, 845, etl;.), the regu­ lar 4-pin rypcs (SV811, SVS72), and a specially-modified 829-type socket to hold the Russian GM-70 tube. A blank space was left for the output transformer, where either clip leads or wire nulS were used to altach to the transformer under test. A separare wood breadboard hdd an unrcgu-

VACUUM TUBE VALLEY ISSU E 9 TRANSMITTING TUB E T ES T A M P

Table • Transformer Tests 1 Extensive metering was used to insure accurate and repeatable operating condi­ Transformer Pri. Res. -3db HF response tions. In addition to the calibrated HV Audio Note 50W/1 0K.!211SE ...... 158(1 33.9KHz,wfp<"ak at 72.2KHz supply and plate currefl[ meter mentioned above, VOMs and DVMs were used [0 Bartolucci 128 ...... 249 0 19.3 KHz,w/peak at 53.9Klit measure grid voltage, filament voltage, and AC grid drive voltage. Electra·Print KLiOKB·B ...122 0 28.IKHz,w/peak at 79.0KHz Testing Philosophy

Tamura F-2013 ...... 2 9;0 216KHz, no peak The goal of the transformer and trans­ mitting tubc testing was to run the unit

Tango XE6O-1OSNF ...... 32 20 92.2KHz, no peak in a similar environment to that of a real amp. HowC\'er, due to fixed transformer The tr:msformcrs were bench tested with a sine wave oscillator drivin$ the transform­ ers through a 4.7K series resistors. The were: termin;ued Into a non­ impedances and different characteristics between tubes, comparisons between dif­ inductive 8 ohm load. Primary measurements were tried using the Freed \OIl inductance , but there was difficulty in getting the bridge nulled . Later ferently spec'd units (i.e.: 7K vs 10K or investigation showed that at the highest inducrance range needed to teSl these high­ 211 vs 845) are not really \'alid since these impedance transformers 100H), bad paper capacitors in the bridge prevented it have different optimum operating polms. (> from nulling. The lower ran es used mica capacitors. which were OK. Even test However, comparisons of like units are equipment needs re-capping.� (Tlubridgt was rtcapptd btforrany usting was dOf/f. Ed) vaJid. Also, both electricallests and listen­ ing testS would be done. Asboth forms of The Japanese transformers tested well, with good-looking 10KHz square ,"'ave these tests were carried OUt ovcr a period � onsc. Both the Ele<:tra-Print and Audio Note had reasonably good HF respon�, p of several months, preferred operating although were somewhat Jumpy. The Banalucc! had the worst HF response of the points changed. and will be nOled in the: transformers tested in this grouping- but imerestingly sounded quite gooe\! [est resuhs.

Table 2 - Tube TestS (211 types only) Tube Technical Measurements

Tube Type Condition DC Vg AC Vg Power THD Two different measurements were done on each tube': to evaluate: their inherent GE VT-4C ...... used ·SHV H,7V 5.0W \.2% distortion and power OUtput capability. 42.IV llSW 3% Unlike earlier testS published in \TTV, a GEjAN CG-21 I #1 ...... used ·SI.9V 24.GV 5.0W 1.05% standard harmonic distortion meter 43.2V 14.0W 3% (Sound Technology 17008) was used, GE JAN CG-211 12 . _ ...... nt"W ·S3.9V 2S.5V 5.0W 1.3% which captures all harmonics and noise. 43.SV asw 3% To keep hum and noise problems down, a Nalionzl211 (China) 11 ....•.•....new ·4 9.4V 253V 5.0W \.2% 400 Hz high-pass filter in ,he: analyzer "1.8V I1.2W 3% was engaged. The lCS! signal was a 1KHz Nationzl211 (China) 12 ...... nt"W -SO.2V 24.9V 5.0W 1.2% sine wave:. Distortion tests were run :.l[ a 41.9V ILlW 3% constant power OUtpUt of 5 watts (6.32 United CUE38111 ...... usM� ·53.7V H.2V 5.0W 1.1% Vrms across a 8 ohm load). This is higher 423V 14.3W 3% than the: earlier vrv teStS of 1 watt, but RCA 211 (prcY4r) #1 ...... new ·4 9.8V H.OV 5.0W 1.25% the low distortion of these tubes allowed 403V 13.0W 3% noise to dominate al this low power level. RCA 211 (prewar) #2 ...... ncw ·SO.2V B.GV 5.0W 1. 2S% For power OUtput tests, a distortion levd 40.IV 13.0W 3% of 3% was arbitrarily picked �s being well RCA VT--iC ...... used -SO.9V H.6V 5.0W 0.95% into dipping for all the tubes. The "2.BV 13.5W 3% Electra-Prim KL iOKBIOK OUtpUt trans­ WE 211D ...... , .•..., .... used --is.OV 23.8V 5.0W \.3;% former was used for these tests. Thc tubes 38.5V 11.0W 3% were run with a 1000V plate supply SvnlanaSV-81l,1O ...... •...... new -66.4V 30.0V 5.0W 1.35% biased to 60 mA. 52.7\1 14.5W 3% SVl:llanaSV·572,1O" ..... , ...... new -7S.0V 32.0V 5.0W 2.1% The Amerian tubes were remarkably 443V 9.2W 3% consistent in biasing, gain, and distortion, Russian GM-70 ...... ' .ncw -91.8V 34.0V 5.0W 0.8;% with the ReA Vf-4C having the lowest 70.4V 22.0W 3% distorrion at 5\'

VACUUM TUBE VALLEY ISSUE 9

• TRANSMITTING TUB E T EST A M P

Atma-SphereT" Amplifier Kits: Musically Authentic! M-60 Mk. (PiClUred) II Kit $2295 Wans of Tubed, OTL Purity 60

"... Breathe in and out like the music... " GM-lO, G-trOll 845 &SVdllllll SV811-1O -Art Dud/e)' solid, The SV-811-1O was a like a bit Listener, prin S g '97 lower mu 211 - with slightet higher max­ imum output power. The SV-572-10 was Now there's a word rarely associaled with audio gear. By a marginal performer, apparendy due to Authentic? definition "authentic" means Exactly high distortion, The GM-70 was a killer genuine, pure, real, accurate_ the words describing the true note-by-note musical presentation or tube, with low distortion and high power, fill [0 mu Atma-Sphere audio gear. Musical authenticity begins with the designer, This is be expected from a lower tube, whichthe is why the 845s were nOt test­ ed againH 211s, A5 with these Karsten, our Chief Designer, could have easily built solid state all ti Ralph tesl'S, it should be notedquite that the statis cal amps. Karsten, however, has the true desire to build genuinely accurate sampling of tubes is small, so be and purely transparent gear. Solid state cannot do Output it! careful not to draw major conclusions transfonners cannot do it! So Karsten engineered and patented a totally from the data. '1;""0 old Western Electric new design combining, the musicality of two 211 D tubes from the 19205 were tested, within each chassis, singled-ended tube amps with more authoritive bass power than a One would draw normal plate current for single push/pull amp and with output transformer to snub the music. about I minute, then would slump to a no low value and distort heavily. Another used 2110 (lisred in Table 2) worked "... mak' mg filreS 111 ' my souI ... " -Harvey Rose1fherg well, but still had a somewhat variable Positive Feedback pbte current. These old WE tubes use Vo!. No. - April oxide-coated filaments, compared to the 6, 6 '97 thoriated-tungsten of all the other tubes >if; CAj.LNOW for infonnation about our kits and full line of factory-built tested. The plate current on the thoriated­ Class A, All Triode, Zero Feedback, OTL Amps and Preamps! tungsten types was rock-solid.

Summary Quietly Producing The World's Finest Audio Gear! Transmitting triode amplifiers raise the amp construction di fficulty to a higher level than convemionallow-impedance amps: more dangerous voltages, expensive f1T�1\Atma-Sphere Music Systems. Inc, high-impedance OutpUl transformers, The OTL Leader, featuring Balanced Dilierential Design ™ strange tube sockets, locs of heat. However, �rttR� good amps using these tubes have a dis­ [60 So. Wheeler, SI. Paul. MN 55105 • Phone 612-690-2246 • F!lx 612-699-1175 tinctive "big� sound - open, spacious, and www.atma-spherc.com dynamic - that is appealiog. These big tri­ ades are definitely the starting poim for - his is the correct schematic for the Alan the "ultimate" tube amplifier. CORRECTION: VTV #8 Page 12 T Kimmel Amp. use the schematic shown issue OTl Do Not in #8. UPDATEO FLOATING POWER SUPPLY InJPPc1i91 i st 1325110 Ventura6lvd. [ Stooio City, CA 91 t.04 B"� (618) 995.6646 fa•. (816) 995·8(;47

The Ecl«tic Audio/Video Service Center D1 · D4: 1 N4007 ( 1000V , 1A)

VACUUM TUBE VALLEY IS SUE 9 • VTV #9 has an error on the transmitting tube amp voltage doubler power supply schematic on page 10. The is wired wrong and must not short across the power transfonner. John Atwood will be posting the 6AX4GT corrected schematic in the next issue and on http://www.vacuumtube.com very soon. DO NOT BUILD THIS PAGE 10. CIRCUIT WITH THE SCHEMATIC ON TRANSM T T N G T U 8 E T EST A M P

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nG'lCT 6AX�CT ,.- ,. 211 Test Amplifier by John Atwood '.. -

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.� . 'w

appearw in the 1946-1960 period. device today may the Fairchild 670 lK Occasionally used in early computers, the limiter, which can sell for up to 525,000. 670 Uncle Eric's Dumpster premium version 5670 was once widely The is unusual in that it uses twO manufactured. It has controlled warmup gain comrol cells made from four 6386 Type 2C51/5670 and tight specifications on grid current, triodes in parallel. Since it is not used in By Eric Barbaur noise and microphony. The 5670W was any other currem application, and is out 19505 © used extensively in military equip­ of production, old stock can only go up in 1998 memo price. If you want to inveSt in an NOS tube, the 6386 looks like a good bet. The much scaTcer 6385 is the Bendix uRed Bank" version. Its heater draws 500 6854 is very similar to the 6385, except mA rather than 300, and it has an inter­ in an ruggedizcd form with hard glass and nal shield between the triodes. The 6385 extra bracing. And the 7861 is a GE is a super-premium, but not really a better �Five-Star� version with a 12.6 volt heater audio performer than a common 2C51. for mobile radio equipment.

Introduced in 1946 by Western 6386 is a variable-mu version common­ This is a good time to use this family in Electric, this miniature dual [[iode is ly used as a gain-controlled cascode RF audio, as 1980s military-surplus 56705 of allegedly an RF only device. Yet our dis­ amplifier. Ahhough not really suited for good quality are readily available from tortion and listening testS s«m to indicate hi-fi use, it has a special audio application. dealers, at absurdly low cost. So don't high linearity at Iypical levels in an audio The most valuable vintage electronic ignore it. line stage. Later versions were introduced as type 2C51 by Sylvania and Tung-Sol. WE's in-house number for the 2C51 was 396A. The 407A is similar (0 the 396A, but has a 20/40V filament and was used extensively in Bell SyStem carrier repeaters. If grid-plate capacitance worries you, the 2C51 is safer than common miniature triodes, as it is usable up to 800 MHz.

Since it was popular in VHF applica­ 2C51 GE 5 Star Sylvallitl1980s tions, many variations of the Sylvania TUllg-Sol WE 3.96A 6386 2C51 2C51 5670

VACUUM Tu 8 E VALLEY ISSUE 9 la 4 S E L STENING T ESTS 2 / 8 5

845 gave much bncer integration to the VTV Listening Tests: sound and was very musical. Then we lis­ tened to a United Electronics 38 111 (mil­ itarv number) set at 980 volts and 60 ma. This !Uhe sounded clear and integrated, 211/845s and 10K with a less aggressive presence than the GE Vf--4s. The sound was wdl balanced with d«p bass and cx<:dJent dynamics. SE Transformers With this transformer and SClUp. the United 38111 was the ben a,'crall sound­ ing 211. By Charlie Kiltlesan © 1998 All Rights Reserved We obtained an early 1930's WeStern Eler;:tric 2110 and noted the sound to be r------er r- ---i similar to the ReA 845, except the a,'cra!] Over the last Several months, the vrv Timpact on sound quality and p fo staff and a number of local audio enthusi­ mance. For the driver srage in At\vood's soundsrage was a little smaller and the asts have been conducting listening and (est amp, we notoo the 6B4 triode brand tube made less power. The old WE 211 evaluation tests of both new production could change the overall sound quality. had better balance than many of the other and NOS 211 and 845 tubes. The larger For example, the 19405 Sylvania 6B4 had 211's and had good dimension and detail. The early 50-wart triode SE amplifiers have more a slightly congested midrange when com- 211s should be run conserva- power and realism than the majority of pared to the Tung-Sol 6B45; these were tivdy (under 800 volts and 60 mal to 300B amplifiers, based upon opinions cleaner and more detailed in the mids. In avoid any problems. expressed during listening reSUi at vrv. addition, the metal RCA 617s Were not as The last tube we tried with the For the audio enthusiast who simply must open sounding as rhe glass-type Sy vania l AudioNote IOK was the Ulyanov GM 70 have the most compelling sound, 211/845 617GTs, which were lighter and had more - with its h uge car bon an od e. It was set at amps are the way to go. Manufacturers "air." 980 volts and 100 ma. This tube (mu 7) including AudioNore UK, Cary Audio, has a big, authoritative sound, but still Bd Canto. Wa vac and man orhers aTe y demonstrates intimate ddicacy. The bass offering 21 11845 SE amplifiers, bur the is big, but is not as integrated as some of price typically startS at $3500 and up. the 211s and 845s in this resr. With an optimized driver circuit, the GM-70 The series of rransmining tube rdated articles in this issue will give the reader & would make the ultimate heavy metal sin­ home conStructor detailed information, gle-ended amplifier. dccuical test results and listening tests of new and vimage 21 1/845 types. The tube listening test was done in conjunction with our listening e:valuadons of new pro­ duction IOK output transformers using John Atwood's telit amp, described on page 7 of this issue. Additional C

VACUUM TUB E VALLEY ISSUE 9

• STENING EST S 2 I I 8 4 5 S E L T and the mids wi th this combination \V(re ma. This combination with the Eleara­ very engaging and rich sounding. The Prim was excellent, very musical, bm di d­ highs were not as cxtended as the O(her n't have as much dttp bass the RCA 845. transformers in this tCSt, but this could be Nou that rhr is (xtrrmr/y difficult GM-lO a plus for those with sensitive horn speak­ IQ gu and if 1I0tIlllail4bk from any Russian ers who don't want harsh highs. Overall, tub, vtndors at tht currmt timf. the Barto)uccis were: very easy TO listen to, but arc nOl forthe extreme high frequen­ cy detail frc:ak. For those who want a romamic, "European� sound, go with the Banolucci IOK unitS.

made and has ex<;ellent<;haracteristics. With the GE VT-4C. the sound was refined and polite. almost <;ourreous. Even though the unit was sweet and dynamic, the soundstage seemed smaller than many of the other transformers in this test. The Ta ngo had ex<;ellenr high frequen<::y measurements. Sound improved with better bass, detail and bal­ Tamura an<;e using tbe 38111. RCA 211. RCA We sampled the beautiful and huge 845 and Cetron 845s. Tamura F-2013 !OK SE unit. Using the Conclusions GE Vf-4C. Ihis Hansformer had me deepest bass. dean and a<;<;urate mid-fre­ After listening to the 50 wailer fami­ all El ectra-Print quen<;ies and super-extended highs. ly transmining tubes in this teSt, we came However, th e P3<;e and timing were a bit to some enlightened wnclusions. The For this test, Jack sent us rwo versions slower tban tbe AudioNo(e or the Electra GE-vr-4 is the most common NOS type of his KL10KB, IOK SE output trans­ Print units. Next was the 1943 RCA 211 and works very well. Improvements are former. This hunk of iron is huge and that gave a <;risper, fuller and more three­ made by using the RCA type 211 and appears to be extremely well-made. The dimensional sound than the GE VT-4. 845, however, these tube are now very second version has more extended high Then we plugged in an RCA 845 set at rare and NOS examples <::an <;os[ over frequency response than the firS[ proto­ 950 volts with 65ma plate <;urrem. This .$300. ea<;h! The United Electronics type we reviewed. Again, scuings on out­ combinalion was detailed with very dear 38111 is an cx<;ellenr 211 type, but is put tubes were 980 volts and 60-ma plate sounding instrumentS and voice repro­ even harder to findin any quantity than current. unless otherwise noted. The first duction. The bass response was eXlTemcly the RCA ty pes . The glass t' ped WE tube we tried with the Electra-Print was convin<;ing and optimum. The next tube types as well as the 242 anl 284 types are the GE Vf-4 that exhibited a big sound. wc tried was the SV572-1 0 which was extremely rare collector's items and <::an but was somewhat fo rward when com­ powerful. dean sounding and had an low COSt over S500+ ea<;h in NOS condition. pared to the lower mu 845s. This tube noise floor. The 572 did nOt have the Svcdana SV572 and SV8 11 types are has good anack, with super-extcnded power or bass response of the larger !Ubes. unique tubes that we know sound good in mids. Next came a 1974 �intage, Then came the United Electronics 38111. circuits optimized for them. American-made Cetron 845 that turned Thsi combination was a<;<;urate, involving out to an ex<;e1lent sounding tube (close and balanced sounding. The response The best buvs are the Chinese-madc 1"0 the RCA 845), very musi<;al with a was smooth and very detoliled witb great 211s and 845� whi<;h <::an be pur<;hased sparkly sound. The SV8\ \-10 worked top end. Overall. a "real- sounding tube for under S50 each. The Chinese 21 1s well with the Electra-Print, giving dean, and transformer combination. Lastly, we had good mids, but the bass w,u softer balanced sound. The SV572-\0 was sim­ used the CetrOn 845 that gave a super and highs thinner than the others in this test. However, these have an ilar in sound, but did not put out as balanced sound with clean powerful tubes much power in this SCtup. Then we Hied pun<;h. The Cetron with tbe Tamura is expe<;ted servi<;e life that is signifi<;antly the United Electronics 38111 with the very a<;<;urate and musical. The Tamura less than any of the Ameri<::an types. The Electra-Print; (hat resulted in a bigger has more of a hi-fi tilt, bur in some best new produ<;tion 845 is the bonom-end and a wider bandwidth. This speaker systems with sensitive barns, this Richardson-Cetron 845 that is <::UTfently «American" combination was a little for­ characteristi<:: might sound a linle si:ZIly. being made at their facility in La Fox, ward sounding, but not harsh in any way. Overall, the Tamura appeared to be the lllinois. A(:(:ording to Ri<;hardson offi­ Then came the RCA 211 whkh proved to best made and had the deepest low bass. cials. they have the original RCA tooling be musi<::al and involving. This <;ombina­ and equipment for tbe 211 and 845 rion had good timing and sweet. seamless Tan go types. If you want a new, reliable 845. the Cetron is the way to go. These tubes will detail. Next, we plugged the RCA 845 Many Japanese OEMs used Tango iron last mu<;h longer than the Chinese types, imo the socket and nOted a similar per­ in their tube electronics productS. We fo rm,mce to the RCA 211, but with deep­ are easier to source and <;ome with a sampled the Tan go XE-60-10, 10K SE fa<;tory warranty. er bass. Then <::ame the Ulyanov GM-70 unit. This transformer is beautiful. well that wc ran full-rih at 1000 volts and 120

VACUUM TUBE VALLEY ISSUE 9

• THE A M PEG S V T

The 8-15 Portafla

The move ro Li d The Ampeg SVT: en marked the � nin ng inthe February 1962 of in of Ampeg.modern Their need for propelled History and Va riations era-an era change-forwas theirgrowth fir$( {rue dassic--theby Jess the: suc­ cessOliv of de g ed 8-15 Ponaflex er in si n n rp r ed(inuo­ an innov­ © 1998 All co By Terry Buddingh RIgh' RereNed ativeducerectifier.r ess),Other a pair ers iof 616s,u e 5Uand4 a r d- to develop ua by ns h was during e o that l e ga State rectifiers, v o s ands o so b rnthe Ampeg officially enlisting ty a reputation for q i 12AX.7s,719 9s, o . i u o Oscar Pettiford. For historical perspec i e ir's important endorsements from esteemed 7027s. to that 's brilliant innovator players like jazz. v rt os 8-15 would become the industry t v To fully understand Ampcg it's neces- standardThe r in e Lloydknow Lo r experimented with electrified sary understand Everen to Hull and Jess role the rede ne. d by bass ae and fo recording wasth '60s The late: Oliver. They were professional great James Jamerson. who pl ed hi Vega th Rickenbacher of electric bass fia in '20s. regularlyboth perf rmed and and ? the y 8-15s were selling electric uprightLeo basses dard and u es of their day. hey bassistS that 1t�e stan- '62 manyFender gigs Precision and some bass re Throughcordings a T inuoducedamps by his the first '30s Prec s n Fender'51 n decades meticulously refining the p jazz t n on a -up co ceptio . how-o i ioin bass'52. in of d s e t ever,e r a commonnoted mis thatn n, and his first 8assman amp to protect and defend The firstamplifiers the nuances their craft. They fe lt it was the Motownit should hits be recorded a onhe most am oofs thetheir music responsibility they loved from the � rud , new Ampeg Com panyproduced were designed by KHitsville USA" studio n tet t oit,f the u loud, and vulgar� c e D he great with a d were recordedi r dirc:

The sounded great 8-15 progressed­in the tc:

Hull and Oliver would tubborn re t i t n e t ckn wledge thes hanglying s s 1969-70 SVT(h assis c he e d o a o

VACUUM TUBE VALLEY ISSUE 9 THE A M PEG S V T

1969-70 Ampeg 1974 Amptg SVT SVT

1977 Amptg SIT J 980 Amprg SVT Uapanm verrionj times until 1967, when a group known as {ieal [Q a 8·15 preamp, with a few ated-tungsten-filament power triodes run­ UNI Music began to purchase Ampeg changes in component values, and a few ning at 1250 volts! (It evolved fr om a stock. By 1968 UN! Music had acquired minor embcllishmel\l's. The 8-1 5 and record cutting amp that Bill built prior to sole ownership of Ampeg. Fender and SVT (as \Vd] as many other Ampc:gs) used the svr's dcvelopmenr.) It was decided Gibson were dominating the marketplace [he same tone control filter network that this was perhaps a little toO danger­ with products that appealed to the rapidly which incorporated a primitive integrated ous for a consumer product and an alter­ gtowing number of rock players. Ampeg circuit comprised of twO resistOrs and native, lower voltage OUtpUt tube would had an image problem-they were still four capacitors. Channel I can he be used in the production models. building amps with accordion inputs! It thought of as an extremely embellished 6146B/8298A beam power tubes had was finally time for Ampeg to assert itself (or hot-roddcd) 8-15 preamp. The Ultra proven their ruggedness in taxicab twO­ as an industry leader by producing a truly Low circuit is further embellished 10 pro­ way radio service. What environmenr earth-shaking product-the higgest, bad­ vide a Bass Cut feature, and is driven by a could be more harsh than a New York dest, most impressive bass amp ever seen. cathode fo llower (thc "I2AU7" ponion of City taxi? the 120W7/7247 which is a dissimilar The Ampeg svr dual Hiode tuhe equivalent to 1/2 of a Bill Hughes would accompany Ampeg's 12 1/2 of a 12AX7). The most newest endorsers-The Rolling Stones­ In the late ' s the Acoustic had AU7 and 60 360 on their 1969 "Gimme Shelter» toUT. established itself as the bass amp of choice unique feature of Channel 1 is its midrange comrol-it uses a tapped Crude, loud, and vulgar, The Stones epit­ for the discriminati ng player seeking the roroidal to select the midrange omized everything Everett Hull hated ulti mate bass tone (and volume). It center frequency. The choices are 220Hz, about rock music; his teeth are probably became an obvious target fo r the Ampeg 8001-lz., and 3,000Hz.. It also uses twO still grinding! The band tonure-tested design team. Their mission was dear­ , additional " 12AXr stages and one more the new obscenely heavy 82 pound, 300+ beat the 360 in every way possible. The watt svr (and its alias the V-9). Keirh 360 sounded dry and one-dimensional "12AU7� srage derived from 12DW7s. Richards and Mick 'laylot plugged them due to its all� design, and its The twO channels sum inro a 6C4 (simi­ lar to J 12 of a 12AU7 used as a cathode illlO 4xl2 guitar C3bs, while Bill Wyman folded-horn speaker cabinet design ) used the new 8x I 0 bass cabs. Their live sounded good in a big room, but sounded follower. It's obvious Bill was fond of the album "Get Yer Ya-Ya's Out!" was record­ less than impressive up-dose. low impedance drive characteristics of a 12AU7 (or equivalent) used as a cathode ed during this tour on November 27th & 28th at Madison Square Garden in New Ampcg's Chief Engineer Bill Hughes follower! r Their rather dean guitar a was responsible fo r the design of the Yo k City. nd svr The prototype SVT (shon "S pe bass tones were obtained at what were circuitry. The svr's preamp was derived for u r from the B-15. Channel 2 is nearly iden� Valve Technology") used four 811A thori- most assuredly excruciati ngly loud volume

VACUUM TUB E VALLEY ISSUE 9 THE A M P £ G S V T

1963-70 SVT with 6146r 1980 SVTwirh 6550As Oa pnnJ

levels. While the 6146B/8298As held up thunderous! OK, so the cymbals were connol's primitive integrated circuir. to the rnechanically abusive environment practically non-existent, and the other Ampeg was sold to Music Technology Inc. of taxi cabs, they were shown to be less instruments were more than a bit over­ in 1980. The eiec([onics were assembled tOlerant of the abuse provided by the shadowed, but fr om a bass player's poim­ in Japan and the cabinets with spring­ Rolling Stones-they would self-destruct of-view, this was hi-fi heaven. The SVT's loaded handles and cut-away tops were when pushed into for extended monStrOus dynamic range was apparent made in the US. The most obvious elec­ periods. Which, of course, the StOnes did on Ahmad Jamal's "The Essence, Part I". trical differences aTC in the foreign looking continuously. The would soon be Ahmad's playing displays masterful transformers. They also reduced the B+ svr redesigned for six 6550 beam power dynamics, with gentle caresses swelling to voltages by about 5%. Perhaps not quite tubes. out-right assaults, and the SVTs conveyed as beefy sounding as the Magnavox era every ouncc of his powerfully dynamic amps, rhey'n: still capable of producing a Roger Cox designed the 150 pound performance. The piano sounded as big as sweet and pleasant tone, favorcd by some 8xl0 speaker cabinet. It was intended that a house! Don't get me wrong, I'm not for that reason. The reduced voltages also each head drive twO cabinets for a svr advocating SVTs as hi-fi amps; they really increase reliability slightly. In 1986 tOtal of 16 speakers! In controSt to the don't have anywhere near the kind of clar­ Ampcg was purchased by Sr. Louis Music. Acoustic 360's long-distance fo cusing ity, resolution, detail, or extended fre­ They revived the SVT's waning prestige folded horn, the cab was designed to svr quency response that you would expect by reissuing a limited-edition run of 500 pressurize your head at point-blank range. from even an average hi-fi amp, b\l1 jf SVTs using the same pans vendors as the It was designed 10 blow away the Acoustic you're a hard-core bass fiend, it's a sound Magnavox-made Ampegs. Due 10 limited 360 where it mattered most-the music you'll never fo rget. availability of 12DW7s and 12BH7s, the store! It used eight 32 ohm speakers wired current SVI"s have been redesigned to use in patallel for a total load of 4 ohms per Estimating Year Of ManufaclUre the more readily available 12AX7s and cabinet. Each horirontal pair of speakers The 6 1 46B/8298A version would laSt 12AU7s. The preamp has been signifi­ resided in its own scaled enclosure. cantly simplified, but the ower amp is ulllillate 1970, when the output tubes Essentially, four 2x 1 Os were stacked on r would be replaced by 6550s. The earlicst very similar to the origina . The output top of each other. A totally revolutionary amps can be easily identified by their cronsformers are still manufactured by and unptecedented approach to bass short black plastic toggle switches and ETC of Paramus, New Jersey. The power s eaker design! In head-to-head shootouts p blue lettering on the fr ont-panel. The transformers are provided by an off-shore the SVT would annihilate thc Acoustic source. back panel reads: The Ampeg Co. Ine. 360. Bill Hughes and Roger Cox had Linden, N.J .. Rock bassists who prefer to accomplished lheir mission-m build the The new Fender Rumble-Bass amp has use guitar picks rather than bare fingers meaneSt and most impressive bass amp on a preamp that's even less similar TO an find the 6146B/8298A amps have a par­ the planet. It's still the standard by which SVT, but the power amp design is almost ticularly aggressive midrange grind that is all contenders must be judged. identical. Bill Hughes now works for especially enhanced by their pick anack. Fender and apparently he knows that the In 1971 Ampeg was sold to Magnavox As A Hi-Fi Amp� power amp is a classic that can't be svr and the manufacturing was moved to the svr topped. JUSt for ki cks I set-up a pair of SVTs in Magnavox factory in Greenville, my hi-fi room and accessed the power Te nnessee. The early Magnavox amps can Care And Feeding Of An amp sections through their line-in jacks. be easily identified by their mcral lOggle svr It became quickly apparent that the gigan­ switches and the lettering "Division Of Most SVTs were shipped with Mullard ric-ness of the SVT's sound comes from, The Magnavox Company» on the back made 12DW7s. These were extremely at least in parr, rhe power amp. From a panel. Later 70s Magnavox amps can be well-made and great sounding tubes. If hi-fi perspective, the top is extremely you find an with the original identified by the plastic rocker power svr rolled-off, but the bottom is huge! And switch and rectangular pilot light. The Mullards, chances are they have many over 300 watts per channel of tube power hours of service-life left. They have a Magnavox era amps are generol1y favored Strong, muscular sounding midrange drive provides an incredible dynamic range. for their huge and deep bull dozing bot­ Victor Wooten's bass on Bela Fleck's tom end. More accurate estimating of the that makes them the perfect choice for the "Flight Of The Cosmic Hippo" sounded date of manufaCture can always be accom­ world's meaneS[ bass amp. A Telefunken like he was thumpin' away right in ftont plished by observing the date codcs on 12DW7 in the first stage of channel I can of me! The notes on his low B string were potentiometers, filter caps, and the tone add a hint of subtlety and refinement, if

VACUUM TUB E VALLEY ISSUE 9 .. THE AMPEG SVT

, " ' .;' '-1' ;I ; " OWI�H 1'\9 , ,- , i·�· - Yi � , h. ,. . ' �i1. . . - .:. I" . ��; , "-,. -j: " C,' [ . I""!J� , " .,f"f' - i', �L-: � � !f. 1 ., .� i�ill .t,: F . f' )i f.. :. " , I, ,� . -::: If '., 'l� r � ...... v, '" " c . .;,; , . ,::::t� • r.: b ..� . _. j: , , .>. :��. -.,-'n .:: }" I� t- �""," .. ¥:r � " . .� �:> •'m",,••,, sS'

VACUUM TUBE VALLEY ISSUE 9

• THE A M PEG S V T

mat's what you're seeking. I've (fied che Speaking of bias, the originally specified should be cleaned regularly as wdl. Early well-known 12AX.7 conversion and found idle currem of 24 ma per tube could be SVfs had the speaker cable permanently it changes rhe sound; 1 prefer the sound of considered a bit conservative. If you attached to [he amplifier; this cable has 12DW7s. I find the General Electric believe you have a sturdy set of OUtpUt seen lots of abuse by now and should be 12BH7s to provide the factest drive for tubes (Chinese 6550s need nor apply), replaced with a speaker jack, since an the Output stage. 'IfY (0 find a matched you might be tempted to try a bit hotter intermittent load on an svr can be quite pair-triade 1 should match triode I of bias. My richest, best balanced, and most spectacular! It's best to think of an svr as the other rube in transconducrance and refined sounding SVf has six Genelex a high performance ", high maintenance cathode currenr. li-iooe 25 should also KT88s idling at about 33 ma each. Some machine, akin to the muscle cars spawned

• match. SVfs wete shipped with Tung Sol in the same era . 6550s-these have an incredibly derailed You should try to match everything in midrange and lacy top hener suited for True tube amp connoisseurs will have the push/pull OUtpUt srnge: comrol grid guitar amps and hi-fis than bass amps. no problem identifying with the sound of resistors, screen grid resistors, and plate Players seeking obscenely deep, ground­ a properly set-up SVf: The unmistakably resistors. Previous tube failures can have pounding bottom will be happiest with round and liquid warmth, the sense of a dramatic effect on the values of thcse the GE 6550s. The sweet and clean multi-dimensional air and space, the pow­ resistors and the tonc of the amp. I've seen sounding Svellana 6550C compliments erful sellse of breadth and depth, and the 10 ohm plate resistOrs that measured over the sound of the Japanese built MTI amps [aut transient wal!op that can be claimed 4K ohms! Also check the hum balance POt especially well, just don't push the bias only by the king of all bass amps-the and bias POtS and resistors. On some amps Ampeg . excessively hard-watch for hot-spots. I've svr the output transformer taps were incor­ found the Teslovak KT88's bias to be rectly wi red to the switch on the e:nension prone to instability and the tubes can arc speaker jack. When rhe extension jack is unexpectedly. The GE 6146B/8298A urry Btlddingh is 11performing bllsssti Ilnd nor in use rhe normal output jack should (with the Rat sides on the end of the a expert. He is a frequent be wired for 4 ohms. Check the color plates) are the most trouble-free, but [ COl/tributor and guirar amp reviewer for code on the schematic. The truly obsessive wouldn't stray toO far from the recom­ Guitar Pl4yer Magazine and relatedpubli� will probably want to replace the 15K bias mended 24 ma per tuhe idle current. carjrms. and drive balance pots with \0 turn Heli­ Then again, sometimes biasing is a leSt of pOtS for less sensitive and mon: stable and your bravery and faith .... precise bias and balance adjustments-the originals are quite touchy. Other mods The preamp's rocker switches can get have been implemented to reduce bias-pOt dirty and intermittent and cause noise sensitivity. and volume loss; they should be checked and cleaned frequently. PotS and sockets Tub e Lore �ij�LECTRA-PRINT A AND REFERENCE FOR USERS COLLECTORS For serious users, a new look into tubes from 1920 AUDIO to the present: history of design trends, "where us­ ed" information, tech data, equivalencies, "user's if(J even auction prices. Sce e iew by Eric guide,H r v QUALITY HANDWOUND S.E. OUTPUT TRANSFORMERS Barbour in the Winter 1997 Contains 186 pag­ VTV. • Primaries from 1.8K to 10K es, x softbound. Orderable from: 8_V2H I1H • Exclusive wideband design • 820-5411 Supply, (602) • 16, 8, 4, or 2 ohm secondary Antique6221 Electronic S. Maple, Tempe, AZ 85283 • Gold plating • (508) 371-0512 Antique Radio Classified. CUSTOM-BUILT POWERTRANSFORMERS/CHOKES PO Box 2, Carli le , MA 01741 s • Wound to your requirements • Museum of Radio & T h l Bookstore ec no ogy • Heavy·duty design for Class A use 4204 Thorn p e A pl Ln., Charleston, WV 25313 • DC filament supply windings • W7FG Vinlage Manuals, (BOO) 807·6146 • HV chokes to 15H, 300ma 4 3300 Wayside Dr., Bartlesville, OK 7 006 • low voltage, high current filament chokes Or order directly from the author: Component pricing and specifications catalog available Ludwell Sibley Main SI. ELECTRA-PRINT AUOIO 44·VE. Fleminglon, 41 17 89108 NJ 08822 Roxanne Drive las Vegas, NV postpaid: in US Canada, 702-396-4909 FAX 702-396-4910 Price ifordered direct, $19.95 or $24.95 ppd. elsewhere. Discounts available to groups on orders on quantity purchases.

VACUUM TUBE VALLEY ISSUE 9 .. THE R S T PERSONAL COMPUTERS F Computing With Tubes: around 1954, had similar problems. The first programmable computers 10 use were experimental units, hybrid in construction: RAND The Savage Art Corporarion's JOHNNlAC in 1954 and Lincoln Labs' TX-O in 1955. The' firs! all­ mmsistor C3lc aring machine 10 be ul 3. The First pes Were Not Made In 1975 demonstrated, a multiplier built by Bdl Labs in 1951, used point-contact devices By Eric Barbour All and wa5 unrdiable. Further, the first pro- © 1998 Rights Reserved grammable all-transistor computer, Bell 1------,------1Labs' Leprechaun of ! 956, was an experi­ The so-called �digital revolution" contin­ sounds, the "personal computer" predates memal rolOt}'pe only and was nOl manu­ ues to steamroller on. Driven by hype and even the use of transistors! For by 1955, facture/ due 10 reliabiliry issues. Until the avarice, this movemem is fa cilitated by numerous small computers were in daily supply of junction devices was steady and rhe public maunderings of a gang of use in scientific and business data process­ consistent in quality, they had to be indi· remarkably ig norant journalists and self­ ing. All were intended fo r use by a single vidually selected for computer use. Special appointed visionaries. An excellent recent person, and most were no larger than a computing tubes were far more consistem example was a spec al section in the SIIII typical office desk. These machines tend­ i and more reliable. jOSf! Ml!rcury Nl!wl ofMarch 2, 1997. In ed to have a typewriter for input-output, this slI,Pplement, called �Behind The usually the popular (and slow) Friden So: up to 1958, building a computer Wave, various MERe scribblers were Flexowriter with paper-tape reader/punch. meant using tubes. Luckily, the availabili­ i gve n plenry of space to blather about And nothing dse. Some of the larger ty of decent germanium diode!; made the how the Internet has become essential to machines could suPPOrt a pen plotter, a logic circuits of computers smaller and human existence, such that even looking line printer, perhaps a magnetic tape drive simpler. Even so, switching and buffering for a job require!; e-mail and rhe Wo rld or a simple CRT for primitive vector­ were done wi th tubes. De!;pite misconcep­ Wide Web. Overall, it looks like a busi­ based graphics. Yet these are all basically tions about tubes constantly �burning ness-friendly puff piea, of the sort com­ "personal. � And most scandalous of all, OUt," some machines ran for months at a monly seen in daily newspapers around not only did these machine!; contain no time without fail ure!;. Nearly all the the United Srare!; and intended IQ make integrated circuits, they did nOt even use things we take for granted today in com­ loal advertisers fed warm and happy transistors! puters were developed with tube technol­ inside. Yet this particular item simply ogy. If more proof is required, following regurgirated the long-hdd homilies about Why� Well, the semiconductor device!; are de!;criptions of the world's first per­ the development of computing--many of of the early 19505 .....ere very primitive. So sonal computen. You won't find a single which are distorted, if not outrageously liule was known about this technology transistor in any of them. false. that early point-contact devices, commer­ cially available Ask any Silicon Va lley engineer: what (and expensive G-15 was the fir$[ personal COmpUTer? Since for many years), Btndix (Courttry there is no hard-and-fast definition of a were in faCt bare- of rht PC, you will encoumer as many ly adequate for answers Compfltl!TMWl!flmJ as there are engineers in Silicon Va lley. If use in pocket the person being asked is knowledgeable, AM radios. The the mOSt likely responsc will be the MITS Ml!rcury News Altair of 1975. This was the first PC to be people claim that � � I wi dely available 10 hobbyists, at a �Iow the invention of co5c�--whatever (har means. (Thesc folks the transistor in usually fail to mention even earlier 1947 c anged machines: IBM 5100, Scelbi 8H, Micral.) compUTIng,� yet Yet one could make :10 c:xcellent claim for they seem not to the idea that -personal computer" is a know that tran­ fairly broad category, which immediately sistors were awful eclipses even the 5100, Scelbi or French­ until ci rca 1958. made Micral. At first they were point-contact, If we want to define a -personal com­ had low gai n and pUTer" as physically small, generalized in vcry high noise design for a variety of scientific and com­ figure!;, varied mercial use!; and imended for use by a enormously from single operator, then these early micro­ sample to sam­ computers are left in the dust. If you're ple, and were picky, then the Digital Equipment anything but Corporation PDP-8 was a personal com­ rugged. Junction puter. devices, which tarted t appear Yet as horrible and heretical as this � '? In quantity

VACUUM TUBE VALLEY ISSUE 9 • THE F R S T PERSONAL COMPUTERS

£101 mem with their massive ugliness. By com­ (CmrtayCompurer ofrIx parison, the Librascope computer had Museum) loads of STYLE. And it COSt a mere $39,600, a pittance at a time when typical mainframes wcce $200,000 and required a sIafT of 3 to people to keep them run­ . 10 nmg. The: LGP-30 was remarkably advanced, in sp ite of the lack of transistors. Irs inge­ nious design, by Dr. Stanley Frankei of Cal Te ch, used a minimum of electronics and was totally serial-synchronous. Operating registers could be displayed on a small eRT. Main memory was 4096 worru on a magnetic drum, and given [hat a word was 30 bits long, the LGP-30 had far more memory capacity than the early Altairs--in fact, about as much as the original Apple IL Only 112 and whes 1500 germanium diodes were enough to do everything required. Sixteen machine instructions, and why have any more? Input and output was by F1exowrirer, and Bendix G-15 length encoded each digit. A word was 12 adding peripherals was difficult at best. digits wide plus a sign bit, �nd 220 words Imagine a big art-deeo-like refrigerator Add time was 8.75 milliseconds, very fast were stored on its magnetic dtum. Adding compared to similar machines like the from the 1940s, and you'd have the C-15, tOok 50 milliseconds due to the time-divi­ one of the mOSt popular computers of the Burroughs El 0 I. This slick little gadget sion scheme of its logic. and due 10 the weighed 800 pounds, used 1500 watts 50s. It was simple and small enough to slowness of the drum memory. use in a typi cal offi ce. Memory was a and required only a small window-type air magnetic drum, as usual for this period, [t and the similar E102 had a plug. conditioner in warm weather. holding 2160 words of 29 bits each. 10 board panel, removable allow exchange. Since the drum held data with the Registers were on a special fast-access pan Parts of program flow could be set up on power off, there was little need to re-enter of the drum. Adding twO single-precision a panel, so the program would refer to the operating software when power was numbers took a blinding 540 microscc­ panel settings. This was thought to make switched back on. And a good thing lOO. onds--slowed by the need to access the the programs shoTter and simpler. The since it had to be re-entered from a drum, typical for all drum-memory keyboard and printet were a Butroughs punched tape at 5 characters per second, machines of the day. Even so, at the time �Sensimatic" console, modified from its which tOok more than an hour. The basic this was a fai rly faStcomputer. normal business-accounting uses. system had a simple console monitor and Programs were read from a paper tape Unlike rhe LCP-30 below and some subroutines for computation. Reliability operating at 2 characters per s(X:ond.The was apparently excellent, with no service others, tile C-15 could accept various E101 consumed 3000 peripherals. Magnetic tape drives, paper � wattS and weighed =������ t�pe and c�rd punches, and even a plotter � 1800 pounds. It should ������ were �vai1able_ A basic C-15 used 400 � be easy ro see why the =�=�;�;J tubes, mostly 59675, and 3000 diodes. E101 was quickly Addition of peripher�ls required �n exter­ eclipsed by faster Il�l interface c�binet. Operating uptime machines with more was reponed to be 90-98% for typical memory capacIty. users, m�ny of which were defense eon­ tmctors Of state highway departments. It Librascope LGP-30 is reported th�t the Nebraska Highway Department was using a C-15 until 1982. This was unquestion­ Considering that more than 200 C-15s ably the coolcst, were sold between 1955 and 1960, it's hippest computer of surprising that so few have survived. the 1950s era. It was styled by professional Burroughs EI01 and EI02 industrial designers, and wrapped in a slick Onc of the first desk-sized computers, metal case with a the El 0 1 was wildly popular with defense chrome accent suip. contractors and military agencies, as well Other small computers as b�nks and other kinds of companies. usually were sold in More th�n 80 h�d been sold in the first4 ugly grey or dark-green years after the 1953 introduction. Tt used boxes, intended ro upulse_coded decimal," me�ning it was impress the manage- not capable of static operation--pulse

VACUUM TUBE VALLEY ISSUE 9 THE FIRS T PERSONAL COMPUTERS

technician being needed on the company be ignored and belittled. So it is with Ihat staff. Tu be failures occurred only at inter­ Mercury News piece, a litany of self-ser­ vals of weeks, comparabk to that of many filled with corporate p paga a. vice ro nd rtallsinorized mainframe systems of {he One cannot take seriously a piece of I 960s. ·journalism� which claims that the only importam Ihing 10 happen in compuling The lGP-30 sold until more powerful between 1947 and 1957 was the birch of small compurers, such as the IBM 1620 Bill Gates; which does not menlion any (which was apparemly imroduced specifi­ of Ihe important pre-ENIAC machines or cally to compete with the Librascope), any som'o'are developments of the 1950s. appeare 1959-1960. A few LGP-30s, d in Their Readill:m achine: was aimed at such as the first opera ing sysrems and t donated by the engineering firms that defeme CUStomers fo r engineering work, FORTRAN; and which fails to cover originally bought hem, were being used though it also claimed to be suitable the 1960s such as r was milestOne systems of to teach programming in California for business data processing. It had 260 the IBM System/360 and the PDP-8. schools well into the 1970s. Librascope tubes and 3000 diodes in a large cabinet Still, all this is typical of tOday's computer also sold these machines to companies with impressive-looking glass doors show­ journalism. such as Control Data and the Royal ing off all the circuit modules. Rc.dix was Precision marketing firm, wh o then stuck expandab1c, with optional point ploHer, Onc final note: some vrvrea ders may their own logos on it for sale. So, the magnetic rape drive, and an interim regis­ have heard that early microcomputers like LGP·30 was apparemly the first "generic" the Scelbi are t at they sell for ter for attaching IBM punch-card units. so rare h Pc. Royal ran ads for the LG[>-30 in a A word wa� 10 BeD digits, add time was $8000 and up--yet the Scelhi is relatively variety of magazines. 17 milliseconds including drum access, common, compared even to popular tube and [he drum held 4000 words. A feature computers like the LGP-30 or t e G-I 5. The LGP·30 even got its own high­ h not often seen on these smaller comput­ Interesting, that computer collectors level language compiler in late 1959, ers, but standard with large mainframes haven't discovered th machines yer. called ACf-I. Unfortunately its transis­ est" of [he era, was an oscilloscope for trou­ And this article does not even cover very torized replacement, the RPC-4000, was bleshoo ting. Free, at no extra charge. specialized machines, like the Lillon announced at about the same time. This, 20/40 diffe ntial anal)'2er or the Baird Ihe 1620, and other frantica[ intro· Underwood Elecom 50 Atomic 580re autocorrelator. duced transiSlOr compU e 0 the pc:riod t rs r All rhe business-machine manufacturers Hopeful , this informa o about the senl lhe LGP-30 into the dustbin of his­ ly ti n tory by 1960. Librascope later became a tried to jump into the eomputer world eartiest "personal computers" will help to huilde:r of compUler systems for defense during the 19505. Underwood, a venera­ dissipate the historic information void in work, and is currenlly a division of ble typewriter manufacturer, was no which AmeriOln computing currently lockhced Martin. exception. Their Elecom 50 was first wallows. And il should correct some false delivered in 1955, and il fo llowed their ve:rities, repeated ad nauseaum by pc:ople Monrobot III successful Elecom 100 of 1952. Elecom who s o are paid to h uld know better and 50 roughly corresponded to the know bener. Monroe, a reputable maker of mechani­ Librascopc machine, with 160 tubes and cal calculators, entered the electronics 2000 diodes. Wotds were 10 decimal dig­ Bibliography business with the Monrobot series. The its, and the drum memory held 100 loca­ smallest was the 11[, yet another desk full I. Logi l Design of a Simple General­ tions plus the 3 working registers. u of tubes with a Fl writcr on tOp. The Purpose Computer, IRE TransactiOns on exo Apparently the 110 console was numeric first sample was sold to the US Ai r Force Electronic Computers, Stanley Frankel, only, while n alphanumeric printer was Cambridge: Computing Center in 1955. � volume EC6, number I, March 1957. an e tra opc on. With 800 tubes crammed inside, it had a x l 2. A Second SUITey of Domestic not-so-good uptime record of 80%, and The Elecom 50 used 2000 wam, Electronic Digital Computing Systems, outside of hard failures, Monroe rC

VACUUM TUB E VALLEY ISSUE 9 WINTER 998 C E S REPORT 1

audiophile �screechics", while still deliver­ ing a crcdible 3-D image. Great for hours Winter 1998 of casual listening. Ve ry close second was the Thor Audio system, with tweaks cour­ eES Report tesy of Mike Vans Evers. By Eric Barbour © 1998 Now for the part you're all waiting for, the WEIRDNESS: It seems (0 get bigger eachlcar. And every year, there are morc an more vacu­ a) Ralph Karsten of Atma-Sphere was um-tube products. Not only was the showing offhis newest invention: a 300B Winter CES high-end exhibit at the OTL amp. That's whar I said, a 300B Alcxis Park Hotcl in Las Ve gas the biggest OTL. Only four 30085 are suitable to yet, the "alternative" International High­ drive a 16-ohlll load to 20 wans. I heard End Show was expanded to rwo hOtels-­ it and can attest to ies excellence. the Dcbbie ReynoJds and the Howard Johnson on Tropicana. And even though b) Unfortunately, Moth Audio's huge many listed exhibitors didn't make it, 304TL SE amps weren't ready yet, and there were easily 60+ companies showing WAVAC Audio Labs did not have an tube electronics, almost a 2-w-l ratio exhibit of their giant 833A amps. Even so, over solid-state manufacturers. there were plenty of companies that were totally unfamiliar to us. Audiomat, It would be impossible to choose best Musica Nova, Wyctech, plus rhe firm in sound, as there wCfe so many excellent the ncxt item. systems (and a few bad ones), And I did­ n't have time to hear even haIr of the c) Lars-X Audio of Singapore showed demonstrations. their speaker system--a heavily modified Lowther driver in a transmission-line cab­ Best bass: No question, Dr. Bruce inet. Vastly better sound than ordinary Edgar's new 35 Hz folded-horn subwoofer Lowther setups. Driven by their prototype is one of the world's O1ost efficienr cinder­ PSE GAS? amps. Great imaging, and block pulverizers. And of COUfse, his some bass too. matching Series 80 horns are one of the best horn speakers available in the world today. End of discussion, and forget those old Altec or WE theater horns.

Imaging: The Sonic Frontiers amps were outstanding, as were the Lars-X and Single·Ended Output Transformers Viva displays. Still, the award goes to the ������ new Hovland EL34 amp and matching a Reasonable Price rube preamp. Although it was heavily tilt­ and Built in the USA ed in the treble direction, the stereo image I seemed 100 feet wide and showed MAJOR front-back solidity plus height. Note to Mike Kersler: don't change any­ thing! The SF amps imaged excellently and were more tonally accuratc than the Hovland. d) Tim de Paravicini outdid even him­ Best rock syStem: Demeter's 6550C amps, paired with Aerial Acoustics speak­ self by showing an amp that uses tWenty ers, gave a powerful show without any 12AX?s as OUtput tubes. Don't laugh, ir sounded excellent. Ask our own John glare or unnatural treble overtones. Not Atwood about this--he's been experiment­ Designed forparallel operatiOl1 01: to forget Atma-Sphere's syStem, or Moth EL34s. 3OO8s6A$7t, ing with 12AX?s as Class A2 power tri­ Audio's SV572 amp slamming into Vo n etc. 01 S�p.tu� In recently, and reports great resules. 1 2A3s· Schweiken speakers. ode5 $90,25 . ....I\enced triod.· mode One watt OutpUt per tube.. I. Best secret design: David Berning's new e) A brief visit to the Sands Convention I�".8k�:'-=- primary SVRll amp, using obscure RF switching Can bitused with: . ..le. power techniques to get 35 watts from Center uncovered three car-amp manufac­ 300B. SO,SVSl l.J turers using tubes. Planet Audio, one rube. Sounded great, also deserves to �:�10�W ':"'�",,;: -,I�S lclc2c·lcO�I be in the Most Tonally Accurate caregory Poweramper, and Pha"le Audio all used UBT· 3 tube5 as gain srages with conventional along with Sonic Frontiers. . tranSiStor outputs. Pleasanr musicality: Mesa's new Tigris integrated amp, paired with the Samadhi Acoustics cube speaker. Not accurate, bur damn nice to listen to and free of rhe

VACUUM TUBE VALLEY ISSUE 9 VINTAGE A I I N A PAN U 0 0 J

• in order to build up trust. The Internet will ccrrainly change the way vintage Vintage Audio In audio gear is sold worldwide. There are already dozens of audio classified sites, auction sites and newsgroups that catcr to Japan collectors and tube enthusiasts.

This article and others that follow will review classic equipment and related com­ r. Amplifiers and ponents that are in demand in Japan and other places. What mosr people would By Charles Kittleson @ 1998 All throw out as junk could be worth the Rights Reserved price of a new car and more. The prices lined on pp. 23-23 are from Japanese Ever wonder why you can't find any of buyers. Equipment must be in excellent retail audio shops advertisements found in the good old audio gear anymore? Back original condition with no upgrades or John Atwood's 15-year collection of the in the early 1970's a few audio exporters, modifications. It is best to not recap or top Japanese audio magazine, MJ Audio way ahead of �he masses, were quietly rebuild vima e tube equipment that will uchl/ology. Prices are quoted in Yen and buying up classic tube audio equipmcnr be sold to co llectors, as this can reduce you mUSt convert to US doll3Ts. Current and shipping it to eager buyers in Japan. the value by over 50% in some cases. (April 1998) value of the Yen is about Meanwhile, American consumers were They are very sensitive [0 this condition 130 Yen per US dollar. The wide varia­ getting misled intO believing that Pioneer, due to past experiences of fr iends who tion in prices is due to equipmenr condi­ Sansui and Sony audio gear with all the purchased WE gear through the mail that tion and to individual shops that price fa ncy fe atures and switches was better turned Out to be junk. Speakers mUSt items more expensively. In the high­ than the old sruff. Sometimes ' think have the original cones, and vacuum tubes priced shops, buyers in Japan can negoti­ mOSt people were so out of it baek then should be new in their original boxes, for ate IO ta 30% off asking prices. that they didn't realize solid state gear best prices. really sounded like crap. Even thou01 1 Remember that you will not be able to am writing this article now, it shoula have The vintage audio market in places such fetch these prices in the US. What you been published 20 years ago. as Hong Kong, Taiwan, Korea, Sin apore, can expect is anywhere fr om 25 to 40% etc. has recently been strong as wel! . of the prices quoted here when dealing Back in the 19705, dealer/exporters However, these Asian buyers are often less with repunble dealers. Also remember were running want ads mat would offer particular about condition and also more thac demand and prices forany of this to buy your old Mdntosh or Marann open to other brands such as Fisher, equipment are extremely unsnble and tube gear for $100 or less so you would SCOtt, Dynaco, EICO, Acrosound, etc. subject ro wild fluctuations, either up or be able to buy the shiny, new black and The prices they pay, naTUrally, are some­ down. What is hot today may be a boat silver plastic Asian audio boxes. The deal­ what lower. This phenomenon has anchor tomorrow. It is not easy finding ers would then double to quadruple their brought even more "dealerlexporter$� intO buyers that will pay you top dollar, so you money by selling the tube gear to whole­ the fray, many of whom are after any may have to settle for what is offered if rype salers and exporters or directly to retail of tube audio gear and tend to work on you are in a hurry 10 unload the gear. shops in Akihaban, the electronics dis­ much lo.... -er markups. tricr of Tokyo. By the rime gear was The Asian economy is in turmoil right placed on the retail shelf, the price went To day, there are dorens of would-be now, due to the economic bubble which up between five and ten times the original dealer/exporters advertising in the back of burst a few monms ago, so demand on price. Many of these dealers unobtrusive­ audio publications with a typical ad read­ many items may be soft. In addition, ly made high six figure incomes by ing: �Wanted: Mar.l.nn, Mdntosh, younger engineering-oriented Japanese exporting our old audio Mjunk. � Western Electric. Tannoy..... Cash Paid.� audiophiles are not as eager to collect WE Many of these fellows are purchasing the and other vintage gear as the older 45 + Japanese audiophiles were and are very goodstuff from junk collectOrs, garage year old crowd. However, well-ta-do picky about what they will spend big sale pickers and unsuspecting older people Koreans and Taiwanese have become bucks for. They prefer Western Electric who do nOt have a due as to the value of more active in collecting vinrage audio tubes, amps and speakers, Mdntosh tube this equipment. Unfortunately, most of now so the demand is still there. audio, Marann tube audio, Tannoy loud­ the classic audio gear has already been speakers, A1tec LansilJg tube equipment exported. NOTE: Only selected vintage gear is list­ and speakers, JBL loudspeakers and RCA ed on pp. 23·24 due 10 time and space vacuum tubes. The Japanese are particu­ If you have any of this gear and are considerations. A more detailed Vil/tage larly obsessed with Western Electric. thinking of selling it, shop around to get Hi Fi Price Guide (530) is available from Capacitors, wire, resistors or anything your best price. Some dealer/exporters vrv, and is advertised elsewhere in this marked WE demands premium prices. have a direct connection to either a shop publication. This is due, in some pan, to reviewers in or distributor in Hong Kong or Tokyo This article is Part I of a rhru-part srrin Japanese audio magazines writing exagger­ and may be able to pay more. Other relaud to collecting and pricing vinragr ated words of praise about the virTUes of dealers may have to go through twO to WE equipment. On the other hand, there three "middlemen" or wholesalers. Of audio rquipmrm and rrlaud accrssorirs. is little or no demand for many other vin­ course, each middleman has to take his tage audio brands, such as Scon or Fisher. ·cut.- Some individual sellers have been A sp tcial thanks to HiIllShi Ohuulta, Stnior successful duling directly with buyers Editor, MJ Magazilu, forhi s assistanct Condition is everything to Japanese from retail stores, but this can rake rime with this artick.

VACUUM TUB E VALLEY ISSUE 9 • VINTAGE A U D I 0 I N J A PAN

Amplifiers and Preamplifiers Low Va lue High Va lue

Ahec 126A (push-pull 6L6 amp) ¥l50,000 ¥350,000 pair 128B (push-pull El.34 �mp) Y200,000 V250,000 pair 256C (push-pull 807 amp) ¥l50,000 \1350,000 pair IS20A (push-pull 61.6 amp) ¥lSO,OOO ¥300,000 pair 1530A (push-puIl 6146B amp) ¥275,000 ¥350,000 pair 1567 (tube prcamp) Y250,000 Y350,000 pair I 568A {push-pull 60\7 amp} ¥l40,000 ¥l90,000 pair 1569A (PPP 6CAl amp) ¥160,000 ¥22S,000 pair 1570B (push-pull 811A amp) Y2BO,OOO Y350,000 pair 287 (push-pull 845 amp) ¥440,000 ¥I,OOO,OOO pair 287W (push-pull 80S amp) ,450,000 111,500,000 pair Ampa S07 push-pull theater amp \1150,000 ¥l00,000 pair 6550 push-pull {healer amp noo,ooo Y250,000 pair Audio Research SP-3 (tube preamplifierl ¥! 50,000...... \1200 ,000 Brook 12A3 (push-pull 2A3 amp) \1250,000...... V400,000 pair Model 10 5eri� (rP 2A3 amp) V300,000 ...... V600,000 pair DYNACO

MK III (push-pull KT88 amp) Y90,OOO ...... \1130,000 pair MKIV (push-pull EL34 amp) ¥IOO,OOO ...... VI40,OOO pair PAS-3 (tube preamplifi�r) ¥50,OOO ...... ¥75,OOO rH�K�C�·;�'"�ri()�"�/�/"''=:::::::-_, SCA35 (EL84 integrated amp) ¥50,OOO...... Vl 10,000 mo {tube stereo amp} Y7S,OOO ...... VI30.000 Fisher SA300 (sttreo EL34 amp) 1180,000...... Y100,000 400CX (tube stereo preamp) YI20,000 ...... 1I150,000 BOC (mono tube preamp) VlOO,OOO ...... YI20,000 Harman-Kardon

Citation I (tube stereo pteamp) ¥!35,000 ...... VI60,000 Citation II (6550 push-pull amp) ¥160,OOO ...... Y250,000 Internalional Projector Corporation (IPC) 1001 (push-pull 6L6 amp) ¥!75,OOO ...... V350,000 pair 1011 (push-pull 6L6 amp) V200,000 ...... V250,000 pair 1026 (push-pull B07 amp) V225,000 ...... V300,000 pair 1027 (push-pull 616 amp) \1250,000...... ¥300,000 pair 1029 (SE 61..6 amp) VI50,000...... \1235,000 pair Langevin

10) 0 (6L6 push-pull amp) ¥250,000 .. Y3BO,000 pair 13B (6V6 push-pull amp) \1140,000...... Y200,000 pair Marantt Model 1 Consoltue (mono ) ¥300,000 ...... Y500,000 pair Model 2 (push-pull EL34 amp) ¥440,000 ...... ¥750,000 pair Modd 3 (crossover) Y300,000 ...... ¥3S0,000 pair Model S (push-pull EL34 amp) Y3BO,000 ...... V600,000 pair Model 6 (stereo adapter) Y150,000 ...... ¥IBO,OOO Model 7C (stereo preamplificr) V350,000 ...... ¥600,000 Model 8B (stereo push-pull 6CA7 amp) ¥2BO,OOO ...... ¥400,000 Model 9 (PPP EL34 amp) 1'1,200,000 ...... Vl,800,000 pair Model lOB (FM tuner) V280,000 ...... ¥650,000

VACUUM TUBE VALLEY ISSUE 9 • VINTAGE A U 0 I 0 I N J A PAN

Amplifiers and Preamplifiers Low Va lue High Value

Mclntosh

Al 16 (push-puIl 6BG6 amp) Y190,000 ...... Y250,000 pair

CI I (tube prcamp) V150,000 ...... _ . .Y300,000 C20 (tube prcamp) VI50,000 ...... V325,000 C22 (tube preamp) ¥250,000 ...... ¥560,000 MA230 (tube integrated amp) V150,000 ..Yl 80,000 MOO (push-pull 6L6 amp) ¥l80,OOO .....¥275,000 pair MC40 (push-pul! 6L6 amp) V250,000 ...... ¥280,000 pair MC60 (push-pul! 6550 amp) ¥250,000 ...... Y350,000 pait WE 124 MC75 (push-pull KT88 amp) V255,000...... ¥410,000 pair Ij pt Amplifitr MC225 (stereo push-pu1l 759lA amp) 'i180,000 .....Y25 0,000 MC240 (stereo push-pull 6L6 amp) !i225,000...... 075,000 MC275 (stereo push-pull KT88 amp) ¥400,000 ...... Y800,000 MI200 (push-pull 8005) YI,200,000 ...... Y2,500,000 pair M1350 (350 wan sweep tube amp) YI,500,000 and up per pair

MR65B (FM tuner) Y80,000 ...... ¥135,000 MR66 (AM/FM tuner) YI40,000 ...... YI80,OO0 MR67 (FM MPX tuner) ¥130,000 ...... ¥175,000 MR71 (FM tuner) VI50,000...... Y20 0,000 MXIIO (runer-preamp) Vl80,000 ...... Y275,000 QUA D

22 preamp, I! power amp 000,000 ...... ¥400,000 pair HH Scott 250 (push-pull EL34 amp) YllO,OOO...... ¥130,000 pair 130 (tube prcamp) VI 10,000 ...... VI20,000 Western Electric Amplifiers 41 and 42 (rack mounted amp) ¥2,000,000 ...... Y3,000,000 pir 43A (push-pull 211 amp) ¥700,000 .... , ...... ¥1 ,500,000 pair 46 (push-pull 205D amp) V800,000 ...... \'1,800,000 pair 57-A (push-pu1l 252A amp) ¥900,000 ...... YI,SOO,OOO pair 86, 86-A (push-pull 300B amp) ¥I,SOO,OOO...... '2,500,000 pair 86B (push-pull 300B amp) V2,000,000 ...... ¥3,OOO,OOO pair 87B (push-pull 845 or 284-C amp) VI,500,000 ...... ¥2,500,000 pair TA 1086 (push-pull 300B) VI,sOO,OOO ...... Y2,500,000 pair 91A (single-ended 300B) YI,600,000 ...... Y2,000,000 pair 500A (91. power supply and speaker) ¥2,000,000.. .V2,500,000 pair 92A, B (push-pull 300B) VI,SOO,OOO .... ¥2,000,000 pair 94A (push-pull 6V61\VE349 amp) ¥lSO,OOO.. , ...... V900,000 pair 109B (push-puIl 6L6 amp) V800,000 ...... ¥900,000 pair WE 86B Typr Amp/iJitr 118A (PPP 6L6 amp) YSOO,OOO ...... V7S0,000 pair 124A-D (push-pull 350B amp) ¥I,OOO,OOO ...... Vl,450,OOO pair 142A (PP 3S0B amp) V700,OOO .....'i1,000,000 pair 143A (PPI' 61..6 amp) ,550,000 .....V680,000 pair We stern Electric Preamplifiers

105A (high-gain program amplifier) Vl,300,000 ...... ¥1,700,000 pair 106A (line amplifier) YI,200,000 ..YI,SOO,OOO pair 120B (low-level pre-mixing amplifier) V900,000 ...... ¥1,250,000 pair 121A (fixed-gain amplifier) VI,OOO,OOO ..¥1,650,000 pair 129B (mic prtamp) VI ,000,000 ...... ¥2,000,000 pair

VACUUM TUBE VALLEY ISSUE 9 D I S T 0 R T I 0 N A N A L Y Z E R S P A R T 2

meter reading in the top 2/3rd5 of the meter scale. This number, multiplied by Audio st the level switch setting, is the IM distor- The Te Bench: tion.

A very helpful modification to the- Distortion Ana'vzers Heathki[ IM analyzers is to add an outpUt jack after the demodulawr stage, before The Audio Test Bench the amp i rudc dCICCWL Connecting this Part 2 J signal to an oscilloscope shows the distor- =- 1998 All don waveform. This is nOt the same as © Rights Reserved 0.: by the residual distortion waveform from a ,°:"0°" �g;' -\R harmonic distortion analYLee, but is ,ocr}, ���(!" If� John Atwood handy in seeing what part of the 60Hz waveform is dis!Orting, catchin overloads and clipping, and in seeing hig� frequ en- (VfV #8, In pan one of this series page this generally worked wdl in showing cy parasitic oscillations. 30) the general conc of distortion tube power amplifier . analysis was presente�r , a short history of Excessive hum in the equipment under A Brief Hewlett-Packard Affair analysis was given, and the philosophy of test could give erroneous readings, Most published distortion measure- distortion analysis was discussed. In this though. The faCt that the analyzerwas mentS are forTHD (Total Harmonic article several actual distortion analyzers completely self-contained was convenient. Distortion). aving only an analyzer will he discussed in detail. In the next and H IM kept me from comparing my measure- last article the interpretation of rhe mea- On graduating, moving to California, to the rest of the world. At a ham sured results will be covered. and makin good money as an engineer, I ments could final� y buy a distortion analY.l.er of radio swap meet, I picked up a Hewlen- To give a good idea of the methods of my own - this time the newer Heathkit Packard 330B harmonic distortion anaiyz- use and capabilities of distortion analyz- IM-5248 intermodulation analyzer. This er. After getting a copy of the manual, J ers, a detailed description of several dis- was solid-state, and had lower residual discovered. [ had only half an analy;:er - i t tonion analyzers that I have had experi- distortion - but was the same concept as needed an external low-distonion sine- ence with will he given. This will he given the older tube-type IM-48. This analyzer wave oscillator! Some scrounging brought in chronological order, based on my expe- gave very good results during my early a solid-state Krohn-Hite oscillator with rience. The personal history serves 10 put tuhe amp experiments, and is still on the good specs. The lowest distortion reading [he use of these analyzers in herspective, shelfas a back-up analYLer. Fig. 1 shows on the 330B was 1 % fu ll-scale, but the and shows the growth in sop istication of the signal flow in the Heathkit IM anal)';:- residual distoniun inherent in the analyz- audio measurementS, both due to experi- ers. er was about 0.4%. After lots of tweaking ence and more capable technology. (upgrading capacitors, selecting tubes, To use [he analyzer in testing a power adjusting pemode screen voltages, etc.) I The Heathkit Years amplifier, the two-tone output is connect- could only get the residual distortion cd 10 the amp input, a suitable dummy down to about 0.15% - nor very good, While an undergraduate, I worked as a load (typically an 8 ohm power resistor) is even for testing tube amps. Another technician for the Columhia-Princeton connected to the amp, and the analyzer annoyance was an odd hand of distortion Electronic Music Center in New York. input is connected across the dumm), at low levels - almost the opposite of The first audio anall'£er I was exposed 10 load. Mter making sure that the low fre- cross-over distortion - in the distortion was an old Heathkit IM·48 intermodula- ency signa (60Hz) is exactly fo ur times OUtput waveform. This is caused by H-P's tion distortion analy£er. Many amplifiers, l �[ e amplitude of the high fr equenc), sig- use of an AC meter circuit that laces the line amps, and tape recordecs wece tested nal (7KH"l), the two-tone outpUt is meter rectifiers inside the overalr feedback on [his unit. We were never really sure brought up until the desired power OUt- loop. This gives a nice linear meter scale, that the numerical readings correlated to put is reached. The analyzer is then but the signal output is nOt linear at low rhe rest of the world, but the unit was sta- switched to the "Level Set" mode, and the levels. ble and we could truSt it for repeatable in ut level of the analyzer is adjusted for readin s on our own equipment. This a �ll-scale readin on the meter. The ana- To use this type ofTHD anal)'rer, the type 0r analyzer was limited to the iY-ler is then switc't ed to the HIM� mode, sine-wave oscillator is connected 10 the 60Hzf7KH7. SMPTE test, which primari- and the input level switch is set to give a amp input, and [he analrler is connected ly exercised the equipment at 60Hz - but across the dummy load connected to the amp ourput. The oscillator level is adjust- ed to give the desired output fr om the "' AC Malar amp. As with the IM analyzer, the input Laval S e ' Leve l level is adjusted to give a full-scale reading I Qulput in the "Set Lever mode. A this point, the L I Test '''M� Osc. � 17KHZ r.--.. Signal In� '" analyzer is switched to �Distortion,H and the frequency dial is tuned to give a mini- + 00", � " tnpuI mum meter reading. Adjust the Balance Osc. I�L:;t control for minimum reading. Repeat High· Pa$S Pass both adjustments for the best null. The � Filler Filter reading remaining on the meter is the I Fig. 1 - Heathkit IM Ana/yzer -a[]- THD.

VACUUM TUB E VALLEY I SS U E 9 • DISTORTION ANALYZERS PART 2

the generator and anal)'Lcr ganged togeth­ er. The oscillaror OUtpUt is automatically Fig. 2 - Sound Technology levclcd, so you don't get errors when run­ 1700B THD Analyzer ning frequency response plots. The THO tester has good auto-nulling, and has a TIIIo . __ • ___ very handy auto-!e-.·e! circuit that elimi­

"," natcs the: need to do the «Set Level" ' ' adjustment each time. My particular 10 OU!",,! modd even had the meter calibrated r------, ,�, dir«tly read power into an 8-ohm load! low·OI I!Otllon OutpU! Sin, Wlve Olcllll!or The operation of the Sound Te chnology f-�'-I 1700B is the simplest so far: set the Out­ put for the desired power level, set the input level switch for a reading in the upper 2/3rds of the meter scale, then Given the limited performance, Technology was the analyzer to have. I size, switch to distortion, and rcad out the and tedious adjustments of the 330B, I had been keC':ping my eye OUt for a used THO. IM measurements use a similar considered getting the newer H-P 33IA onc, but as with any desirable piece of process. As with most newer anal)'"lcrs, the or 334A. The 331N332A is fu ncdonally equipment, the used price was high - sev­ 1700B has a switchable 80KHz low-pass similar to the 330B, but has much lower eral thousand dollars. I finally found one filter and 400Hz high pass filter. The first residual distortion. The 333AJ334A adds for $1200--<1 lot, but justifiable for my is handy in removing high-frequency an auto-nulling feature, greatly reducil1 audio wnsulting work. �junkH from the signal - which can often the tedium. The even newer 339A final! y oeeur at the outpur of CD players or PC adds a built-in oscillator! HowevC':r, evC':n My new acquisition basically worked, sound !;ards. The 400Hz filter is good in on the used nlarket these analY"lCrs wC':re but was not working to spec, and was removing hum and its harmonia; when quite expensive. I decided to stick with somewhat erratic. It apparently had been running THD tests above 500Hz. the Heath IM analyzer. used on the tCSt bench at Pacific Stereo - and had seen a lot of hard use. Although wnsidered obsolete for pro­ The Jump to Sound Te chnology Fortunately, Sound Te chnology still exiSl5, du!;tion resring, rhe Sound Technology although at a smaller size, in Campbell, analp.ers au still dose to the Stale ofthe By the early 19905, I had started doing California. I brought my unit over, and in perfornlan!;e, and are very good for some serious audio consulting work on art submilled it to their standard $750 over­ R&D and servi!;e work. Sonny at Sound the side, and realiIed I needed a better haul. Judging from the number of compo­ Te !;hnology tOld me that they still make a analyzer than the Heathkit. I had noticed nents replaced, it was more like a $3000 few l700s for the US Navy, where the that many audio professionals had a beige overhaul, but they still only charged the lack of digital ci rcuits makes them suit­ and brown bolC on their benches - an ana­ basic tate. I finally had a high-perfor­ able for use in ultra low-noise environ­ lyzer by Sound Technology. A Silicon mance analyzer! ments. Valley company started by elC-Hewleu­ Packard engineers, their first product was The Sound Te chnology 1700B is a very Audio Meets the omput Age C e a FM stereo multiplelC generator. When finely-tuned, all-analog design. It is basi­ r thC':ir scate-of-the-art distonion analyzer, cally a THD analYLCr, but my model also While the Sound Te chnology unit has the precision, doing frequency response the 1700, came out in the mid-1970s, had the lM analyzer option. The residual their timing was perfect: the ulna-low dis­ disrortion is less than 0.002%. The fre­ curves was tedious, and I realized that there was more to audio measurement tortion wars were underway. From the late quencies are push-button seleccable, with 19705 to the late 19805, Sound than just IM, THD, noise, and fr equency response. In the search for understanding sound and and how electronia; affects sound, it became dear thac more different ways of looking at sound were needed. Spcrtrum analysis gives a whole different view of a signal, and is especially good for looking at the harmonic structure generat­ ed by amplifiers. It is now increasingly necessary to deal wi th audio in a digital fo rm. In shaft, I was looking for the ncxt �. level of performance in audio analysis. The first exposure to the lleJ[t leve':! in state of the art audio testing came about , ..-� six years ago when Mike Hague, the 1Oc.t1 -- -.. er-• -=- . Audio Precision rep. gave a presentation to the Bay Area Tube Enthusiasts on their " -- " .:- -t'.- ': System One analyzet. This is an analog , , �=-' ' analyzer thac is fully computer controlled. By using a DOS-based program running on a PC-compatible comput'er, the con­ Typ e 333A Distortion AlIalyzer trol interface and computational features Hew/ettPa ckani

VACUUM TUB E VALLEY ISSUE 9 DISTORT o N ANAlYZERS PART 2

- Fig. 3 Audio Precision System Two (not Including Dlglts/ lnterf8ce Test circuIts)

A 1""",

A Oulpv'1

O.n.r.lOI '"

/,;:;'---''ill 80KHz' ""'•.

could be: updated wi thout changing the My interest in Audio Precision Wa5 5evC:T:l1 different high-performance AID basic analyzer hardware. There \VCreeve n whetted by my consulting work for con\'cnc:rs are available, connected [0 a options for adding a DSP (Digital Signal Summit Audio, where a System Onc, and OSP Ihal can pC'rfo rm standard analog Processor) which could do HT spectrum later a System Two was regularly used for tem {IM, THO, noise, cross-nlk, phali(', analysis, multi-rone testing, and other production tes ting and repair of their ('rc,), FFT spectrum analysis, and MLS sophisticated tests. The only problem was pro-audio products. The ease of doing analysis, the lancr useful for speaker ICSI­ that a fully loaded system COSt as much a automated tests. as well as the availability ing. In addition, the actual SPDIF or good car. of spectrum analysis. multi-mne analysis, AES/EBU digital signal itself can be per­ and digital interface analysis. were really turbed and analrtcd! During the late 1970s and early 1980s, aTtractive. After saving up some money, Te ktronix made a line of high-qualicy and with an assist from the booming The System Two is run from a audio test gear - mO.H designed to fit in stock market, I decided to rake the big Windows-based program, APWIN, which its DM500-series modular tCSt equipment plunge, and gCl an Audio Precision gives the user separate windows for con­ tro ng each subsystem and function. racks. However, as pan of an MBA­ System Two, complete with dual domain lli inspired "'refocusing," Te kcronix dropped (analog and digiral) analysis. At the time The most common method of usin� the r System Two by running �swecps, thei audio line. The key engineers this was written, I've had the analYLer for is involved then started their own company. twO weeks and am just getting familiar which gcnCT:ltc: graphs or tables of onc Audio Precision, Inc. in 1986 to continue with all itS power. Its capabili ties are so parameter \'crsus another. It can also do their audio work. A [fend in instrumenta­ extensive, that ! can only cover the basic single-point measurements displayed on a tjo design at that time was the incorpo­ bar graph or numerical readout on the � . analysis functions here. In the last article, . ration of mIcroprocessors to automate some of the more advanced features will screen Set-ups and captured data can be saved to commands and calculate. However, cqu· ment with be explained. disc. All settings and �embeddedH processors coul :reasily available TO the user arc also available in a become obsolete as newer processors and The System 1wo has basically the same language called APWIN BASIC, which is better software techniques were devel­ signal path as a regular harmonic distor­ based on Microsoft's Visual Basic for oped. Audio Precision decided to use rhe tion analyzer, but with all switching and Applications (VBA). Thi s is a fully-capa­ ever-cheaper IBM-PC as their control level setti ng under (ompmer comrol. It ble programming language which allows processor. The result was a box that JUSt has an extremely low distortion analog sophisticated aUtomated tests TO be: run. had connectors. switching and adjust­ oscillator (cypically 0.00003% or less at All ments were done through the interface 1 KHz) and an analog analysis section If this sounds like an enthusiastic mar­ keting testimonial, it is just because I am program. By using the computational with Hate variable filter and notch filter an excited new owner! I'm sure that some power of the PC and its storage and with matching specs. For those who PUt bugs and flaws will become apparent. printing capabilities, sweeps, graphs, and down audio transformers in a signal path, However, I look forward to probing the automated test procedures could now be it is interesting to see that Audio done. Tt should be nOfed that the CPIB Precision uses transfo rmers in their ana­ outer limitS of sound design! bus (lEEE-488), originally developed log output stage. To rovide �Dual by p In tht ntxt and artidt on distortion Hewleu-Packard in the 19705, allowed Domain" capabilicy, a DSP can also pro­ Imf analyun. somt typ ical givm similar computer control and computa.­ vide D/A-generated analo signals as wdl g mults wi/J bi tion, but tended to be:expensive, and lit­ as SPDIF (consumer), and AES/EBU from various distortion usu. Somt insights tle high-performance audio-specific hard­ (pro) digiral outputs of all the signals on tht inurprttalion of Iht rNults willalso ware was available for the CPIB. available from the analog section, as well bt disnmrd. as some arbitrary and special waveforms.

VACUUM TUBE VALLEY ISSUE 9 • THE GENTLE G J ANT A L T E C 8 W 2 7

After the amp was up and running and a ('ovo-day burn-in complete, it was time The Gentle Giant: to reap my rewards. With dose to 300 warts of thundering audio at my discre­ tion, I soon discovered these amps arc Altee 287W their happieS[ fully loaded. They were originally auditioned on a pair ofThcil CS 3.6 speakers. These WCTe way toO effi­ 1998 Rights Reserved ciem for an application such as this. I By Natalie J. Stone © AI! strapped the transformer for 5 ohms and connected a pair of old Cerwin-Vega 15 inch and 12 inch home speaker cabinets f------r------1It was just over a year ago that I has a nice wide range and doesn't tax rhe alOl1 with my own home-brew 12 inch acquired the pair of Altec 287W ampli­ driver amp. Next the high voltage all Foea! cabinets. Then I set tbe volume up fiers. I had been reading aboU! large tri­ wiring was replaced with high-grade igni­ ever so slightly as I walked down the ode amps For quire some time and having tion wire. Then the bias circuir was street to ensure my neighbors could enjoy played our several scenarios on a pair of reworked: the selenium rectifier was the music as much as I did. I 570Bs, was ready to move on. 1 had been talking 10 Sonny Goldson about Needless to say, thesc amps aren't for oldcr rheater equipment when he said he everyone: ther like inefficient drivers and had something I might be interested in. J lots of load! They have a class B (,dring was, and when they arrived I thought I and they have a plate voltage of around may have gotten in over my head. They 1500 volts. BAD STUFF, MAN! were pretty raw so J set out on the job to restore them. After a week or so I pow­ JUSt to see what the plate transformer ered up one and had JUSt finished the sec­ was capable of, I used a ncon lamp as an ond when it was discovered that the out­ igniter and was able to develop a ten inch pur transformer was shoned. I called arc which extinguished only after I killed Sonny back to ask if he had any ideas. the mains. It never blew the 2 Antp fuse! Out of pure luck he had a source who If I were to equate this amp to a car it had a set of transformers to a 287W. I would be a '57 Chevy. Bodacious looks, obtained the spare set and was back in lots of power, and inefficienc. But whar a business. It didn't take long to realize that ride! They don't have rhe high headroom these giants had a wealth of unadulterated or presence I've heard from amps like triode power. Their circuit design was as Futtcrman OTLs or a Mac MI-200, but simple, if not more so, than a single­ "., � they definitely have redncck appeal. ended amp. Two things were immediately � - One can also see the early influence visible here. There is no fe edback and RCA 805� Tra"m;.nsmitting Tr iode there are no coupling capacitors. This Typ� that Western Electric had on Ahec. Four leaves the input transformer - T5 - as the tubes mounced benchmark style on the most critical component. replaced with a 5A bridge and a 25 Watt- same plane, a plate currenc meter, and the unique starter swirch that rotates. JUSt 50 ohm POt replaced Ra, allowing on-line T5 has twO jobs: first as an impedance look at the W. E. 43A issue #2). tuning. Next. Cl was taken out and an (VfV matchcr, and second as a phase inverter. RC decoupler was added, giving a more Sadly, looking ahead was the coming of I've been unable to track down an origi­ stable output and reducing hum. The last the amps like the AiteC 260A. An era was nal Alrec T5 part number TL 216, so I rwo mods were the addition of high/low tried a dozen or so transformers until I switches on the plate and filament trans­ fo und a Triad HSM-94. This transformer former primaries. I've seen my home line voltage swing rwency volts and didn't want to power down every time I needed co change taps.

After some power up readings were taken, I started trying different driver amps. If you are unable to track down the OEM Aitec A-127 amp, a Macincosh 50W2 or All6 make good candidates. I'm currently working on building a SE/9 1. Electra Print would be my first choice for an OutpUt transformer with a high impedance on the secondary to drive the input of the 287W dircctly, doing away with the T5 transformer. An addi­ coming to a close. Gone were thc days of tional secondary with common imped­ the �Gende Giancs" and their simplistic ances (4, 8, 16 ohms) would allow the ways. In their place was a contorted maze user to drive speakcrs as well as the of RC nctworks, caps and coils, and 287W. enough feedback to kill a concerto. The

VACUUM TUB E VALLEY ISSUE 9 • THE GENTLE G I ANT A L TEe 2 8 W 7

0- ••'.. .. . _ ...... T_� _A..,.-.. ..' ......

,. '­ � ALTEC ' . lANSING ... " . "'" t . •• , • . , 00 A Z87W AMPLifiER ' O'AI. ..."""'" -.­ . , . ... . «.," -". ' '" --. . . _ -

the old ways of Western Electric but can't find or afford one, you're better offany­ way! And for whoever isn't afraid of super lethal power, the ALTEC287W makes an excellent project.

only real carryover was the use of a cen­ but even the old 83 has a smoother tex­ ter-tapped input transformer. Engineering tufe than the 5U4/5R4, etc. Decide fOf was going in a new direction now. But yoursc:lf. At any rate the 866As weren't was it better? going anywhere. At night you can turn Na talit! Stont! if a vacuum tubt! audio the lights down with only the 287W's l!nrhusidJt who worh af an t!lec/rica! uch­ Many halle asked why I kept the two glow for illumination, put on Pink nician in a pow(r gl!nl!ration plant. Sh( is 866A mercury-vapor rectifiers instead of Floyd's Dark Side of the Moon, and expe­ using solid state. Yes, these can be very rience a visual and aural spectacle that also into motorcyc!u, suam iocomotivu and problematic, but once you get a pair that would cause even me great "Harvey MUly, rh( rmoration of an original arc fairly balanced, you can get several Gizmo� to make water! Linotyp( machini!. thousand hours OUt of [hem, and besides You can reach Natalie by email: they sound beuer to me. A lot of people They create an atmosphere that's hard argue against mercury varor rectification, to describe, but for anyone who enjoys [email protected]

VACUUM TUB E VALLEY ISSUE 9 • B ES T V I N TAG E H I F BUY S

friend's. Tubes most likely to be weak arc The Best Sounds in OUtpUt and tuncr tubes, hut check them all an)"'o"ll.y. Tube pins and sockets can he dirty and have caked-on din or scale, Vintage Hi·Fi Under especially the smaller seven and nine pin miniature types. Use a reliable and envi­ ronmentally safe contact cleaner ro spray $350 into the sockets and replace and remove the tube from the socket five times, then spray some more dcaner in the socket By Charles Kittleson © 1998 All Rights Reserved before you replace the tube. This breaks up the din and makes a bener electrical contact. Slide switches, tone ;md volume f------You don't------have to spend-- a ki-ng's---- ran­ �------fo r some people, so we- don't------recommend � conuols, rotary function switches and som to gct a great sounding tube hi-fi this exercise for audio snobs or arro�m input jacks benefit from contact cleaner synem. There are thousands of J 960'5 yuppies. spray as well. I have had excellent results vintage tube stereo components available w�th Caig D-S spray cleaner and preseTv­ fo r a song, which may only need minor Most of rhe gear menriom:J in the ani­ anve. cle has excellent transformers, point to servicing and upgrades. The equipment Avoid pluggblg your equipmellt ill mentioned in Ihis article is nOt for audio­ point wiring and classic, good sounding Th !rtart orhu good-so unding witbout first brill�'lg it up slowly 011 a philes who must have at least 200 watts circuits. bargains our rhtrt you mll} know about, variable AC tr4ll$fomler (VARL4C). If per channel and concert-like realism. but tlurq uipmtn Jisud in ou hear 120 cycle hum, it is most likely Obviously, those requirements will COst t this Ilrtick is r (ommon Ilnd comporatiwly inrxptnsi vt a high-voltage filter capacitor, which the audio perfectionist ten thousand dol­ . must be rcplaced bl:.fore you can safely lars or more. Components mentioned in The funny thing is, though. rhat when operate the unit. Any older capacitor in this article will make good music, even YOll start looking at a lot of the new tube the si nal path can potentially effect the with moderately efficient speakers, and hi-fi equipment, much of il is copied g sound quality of the unit. Most reStorers will be easy to listen to for long periods from designs from rhe 19505 and 60s. all replace them all with newer film types. In of time without listener fatigue. Plus, With the .audio equipmcm buy-sell many cases, the bias re<:tifier in older they won't break the bank, by costing publications plus rec.;mdio.marketplace equipmetH was a selenium type that goes typically less than $350US per unit (1998 and chay.com on rhe Internet, it won't he bad with age and develops excessive resis­ prices). They arc an excellent comple­ difficult IQ locate anyone of these popu­ tance. This rcduces bias voltage to the ment to CD players that nearly always lar components. OUtpUt tubes, causing the plates to glow sound too "digital� and cry for tubes in Repair and Upgrades orange and go bad. The selenium unit the signal path to smooth the irritating must be replaced with newer silicon solid-state edge. Unless you ha\'e high RcsrQr.l.tion can be the run parr of this diodes or a diode bridge. In addition, the frequency h�ring loss and can't tdl the exercise. Actually bringing a vintage electrol),tic capacitors used to filter the difference, you need tubes when playing piece back to life with your own hands! bias voltage must be replaced for best reli­ CDs. It is always a good idea to obtain a ability. schematic diagram of your equipment Most audio stores will downplay the before you �in the job. & sun to ,h«ft Stereo 70 Amplifier d Dynaco value: and practicality of vintage compo­ all wiring an soltlrrj oints. Man] ofthm nents because many of them have never units Win kits alld the builder may lIot There arc more Oynaco Stereo 70s on owned any, but mainly because they want have bad soldering skills. the planet than any other tube hi fi amp to sell you a new system. Ncw tUbe hi-fi ever made. The reason is simple; they are can sound good, bur the price may be A lot of vintage equipmefll is dusty uncomplicated, easy to repair or mod and was staggering. Buying vintage components from Storage and may have caked on dirt. sound very musicaL The S170 a rec­ can be a fun and rewarding experience, Use a soft, new paintbrush to dust the ommended component in many audio plus you won't suffer massive depreciation equipment. Dirt and smudges can be magazines from itS introduction in 1959 as you would when buying new equip­ removw carefully with water, mild soap through the mid-1960s. With 35 watts ment. Buying anything used is a problem and a soft cloth. Rust and corrosion can per channel, )'ou can drive most speakers be a problem, especia lly iffound in mOst sma ll to mid-sized rooms very on chrome surfaces. Some restor­ easily. The amp is nickel plated and has ers use Simichromc paste polish an attractive cage to enclose the amp and with either a soft cloth or 0000 make it safe for households with children steel wool (super fine) on chrome or pets. The output transformers arc the to remove rust haze. Be extremely famous Dynaco A-470 Ultralinear units. careful with cleaning the dial glass For many audiophi les, the Stereo 70 was on tuners to ensure you don't wash their first serious audio amp. It is esti­ the letters off. mated that there are more than 300,000 Stereo 70s in existence, so finding onc You will need to check all the should be vcr}' easy. For more informa­ tubes to determine if they arc tion on the ST70 and other Oynaco tUbe strong and have no defectS. Either gear, sce V1lIlssue : I. buy a late model mutual conduc­ tance: tube tester or borrow a Tube complcment: twO 7199s, fo ur

VACUUM TUBE VALLEY ISSUE 9 • B VINTAGE H BUY EST F S

EL34s and one 5AR4. Sound qualiry: sweet extended hi ghs. due to excellent very musical midrange. bass response can transformer quality. Typial repairs: be soft and highs are nOt extremely replac;e all paper <::oupling and bypass derailed in Stock. unrcstored fo rm. Good apacitors, replace selenium bias rectifier modifications and upgrades can improve with a silicon diode, fo rm and/or replac;e (he sound quality significantly. Typical all c1ec;trolytic C1pac;itors, and replac;e all repairs: replace selenium bias rectifier --- plate and c;;Hhode resistors in the fr ont­ ------with silicon diodes, replace quad filter --- - end of the amp which reduc;es back­ capacitor, replace coupling and byp:l.Ss ground hiss. Modific;;uions indude: tri­ capacitors on circuit board with modern ode c;onnec;ting the EF86 (results in lower very exc;ellent Z56; Dynaco Ultralinear film types. Most moos involve replacing sensitivity. but deaner sound) or replac; units that have a super-wide bandwidth_ e the driver stage circuit board with a cus­ EF86 with a nine-pin dual-triode, tubes and most <::omponents are tom unit and replacing the 71995 with All increase power supply OIpac;itanc;e, etc. mounted on drc;uit boards that an be more llvailable types including 60J8$, kind of brinle if the unit was left on for 6GHBs or 12AX7s. Other moos improve long periods of time_ the power supply with more capacitance and regulation. There were dozens of Tube c;omplement: fo ur 7189/6BQ55, mods for the $T70 published in Audio twO 71995 and twO 1 2AX7s with solid­ Amfjteur, Glass Audio, etc. state rectifier. Sound quality: music;al, bal­ anced and very ple:asing to listen to, even when c;ompared with higher priced com­ • • ponent systems. Ty picaf repairs: in most • c;ases, the EL84 OUtpUt tubes should be replaced :l!j well as the 71995. Coupling OIpacitors in this unit we:re very poor quality and should be replac;ed with newer Fisher and Amplifiers film types. Filter capac;itors should be X-IOI X-202 upgraded to new units. Be very careful Another popular 1960s integrated when working on the circuit boards to stereo amplifier series, the Fisher produc;rs avoid breakage and other damage! A were available in assembled and a5 kits. <::Offimon mod for SCA·3S$ is TO c;onven Several variations were made induding: the driver stage to accept easy-to-find Ornaco and PAS-3 I)reamps X-lOO, X- iOl, X-IOlB, X-lOIC, X-202, PAS·2 6U8/6GH8 tubes instead 0(7 1 99s. X-202B, X-202C, KX-IOO, KX-200. etc. A very popular and good sounding Most driver tube.<; were 12AX7s and OUt­ stereo preamp, the Dynac;o PAS is an PUt tubes were either 7189, 7868 or exc;ellent c;hoic;e for somebody who wants 7591. These amplifiers are full-featured, to get into a cube preamp without buying good sounding and fairly common. the farm. There are do:tens of mods and upgrades published for this preamp because it is easy to work on. Mosl parrs are mounted on c;irc;uit boards, so be c;are­ fu! when replac;ing caps, etc;. The early Mylar and paper c;apac;itOTs in the signal path should be replac;ed with newer film c;aps for the best sound.

Tube c;omplement: four 12AX7s and one 12X4. Sound quality: a very musical pre­ EICO HF 22 and HF 35 amp that c;an sound muc;h bener than Fisher and Receivers EIca power amps are sleepers and 400 500C unitS costing thousands. Circ;uit design real worth c;hec;king OUI_ They are nor espe­ Undoubtedly the most popular tube hi­ fe alUre5 tOne c;ontrols at the end of the c;ially amac;ti\'e, but wually have exc;ellent fi c;omponents in the world, the Fisher audio stage. Typial repairs: replac;e the c;irc;uit design and use high quality OUtpUt 400 and ;OOC rec;eivc:rs are exc;ellent selenium filament supply rectifier stac;k transformers from Chic;ago, Acrosound, sounding units. Although the outpUt with twO silic;on diodes and replac;e the etc. Although many c;ol!ec;tors go after tubes are the hard to get 7868 fo r the: 400 two filament stage c;aps with newer elec­ the higher powered HF 50 and HF 60, and 7591 for the 500C, these rec;eivers are Holytic;s, plus replac;e old signal path the lower powered units are cxcellent worth the effort. Output stage: can be capac;itors with newer film types. Mods when properly resTOred. modified to ac;c;ept either EL34s or indude bypassing the tOne controls and 6L6GCs. These rec;eivers arc still plenti­ beefing up the power supply. Tube c;omplement: HF 22 and HF 35 ful and easy TO find. Transformer quality arc Ulrralinear type power amps with a Dynaco Integrated Amplifier on the Fisher stereo rec;eivers is exc;ellent. Mullard-Type front-end using an EF86, SCA-35 This iron is \'ery music;al and really makes 6SN7 and pp 6L6GC for the HF 22 or The SCA-35 imegrared amp is an exc;cl­ the: unit sound great. EL34 for [he HF The rectifier tubes lenl sounding devic;e. Using push-pull 35. EL84s in Ultralinear mode. the SCA-35 is are either 5U4GB for the HF 22 or 5AR4 onc of the most c;ompa<::l tube stereo amps fo r the HF 35. Sound quality; balanc;ed, available. OUtput transformers are the with good bass, musical midrange and

VACUUM VALLEY 9 TUBE ISSUE • B EST v N TAG E H F I BUY S

Restoration of a Fisher is no! for a 48 and LK·48B; both units arc very simi­ beginner. These units arc: fairly compli� lar in styling and circuitry. The lK-48 c:l.tc:d, but if you have a schematic and was available with a black and champagne the: right parts and test e

VACUUM TUBE VALLEY ISSUE 9 • METALLIC R E C T FIER S

...... C"'o'enrually becomes hi gh enough to affecl Ihe circuitry. Lifetimes are highly depen­ Cathode Bias Metallic dent on the quality of manufacturing, but for a high-quality selenium rectifier, rated by Rectifiers lifetimes range from 1600 hours at 130·C 1_ -- to over 60,000 hours at 40°C. Clearly, John Atwood heat accelerates the breakdown process. Righb Reserved It> 1998 All Another peculiarity of selenium recli­ fien is, like electrolytic capacitors, their r------TC"Verse leakage current goes up while sit­ Long before modern single-crystal semi­ ,1920s and 1- 930s as car and radio lead­--1 conductors became pan o(the electronic acid bauery chargers. The low voltage per ting idle. By slowly rc-applying a reverse designer's repertoire, Umetallic� rectifiers cell and large sizes needed to handle any volrage, the rectifiers can be re-formed. I were available as an alternate to vacuum appreciable current led to them being have experimented with old selenium rec­ or gas rectifiers. The most common metal­ phased-out by the 1940s. However, the tifiers, and fo und that the degree of leak­ lic rectifier is the selenium type, but other high stability of aged copper oxide recti­ age is not nearly as bad as for electrolytic materials were also used. While no! prone fiers kept a niche open for them as instru­ capacitors sitting idle for the same time, le catastrophic failures as tubes are, seleni­ mentation and meter rectifiers (such as so it is unlikely that reformingwould be um rectifiers slowly age and wear out, used in some AC meters and VU meters) needed prior to the first power-up. leading to problems in older equipment up to the preSent. However, if the rectifiers were planned to where they are used. We will look at sev­ be kept in service in top condition, it eral of the different kinds of metallic rec­ Seleni um would be helpful to slowlyapply a reverse voltage up to the maximum PIV (Peak tifiers and recommended ways of replac­ The rectifying properties of selenium ing them. Invcr� Vo ltage) rating of the rectifier. were discovered by Werner Siemens in Copper OJ:ide 1877, bUI the firstcommercial selenium The most insidious problem with seleni­ rectifiers did not appc:u until 1928 in um rectifiers is their potential for emitting The earliest commercial metallie rectifi­ Germany. Selenium rectifiers started to be poisonous gases. If a short-circuit causes a er was the copper oxide type. Rectification used in the United States shortly before selenium recrifier to overheat, it will cre­ takes place at the boundary of Cuprous and during World War 11, and after the ate selenium vapor, which is poisonous. If Oxide (CuD,) and metallic copper. The war essentially replaced copper oxide recti­ this ever happens to you - you can tell by maximum allowable reverse voltage per fiers in all but instrumentation uses. the characteristic pungent smell--dear copper-cuprous oxide junction is typically Selenium was popular because the break­ everyone oUl of the room and open the 6 volts. To achieve a higher voltage rating, down voltage per �cell" (plate) is typically windows to clear the air. This aspect of the copper plates that make up each one 25 volts or more. This made rectifier selenium rectifiers is rarely told in manu­ of these �cells� arc stacked in series. In "sracks� much smaller and more efficient facturers' literalUre, but was well known higher-power rectifiers, the plates arc than copper oxide types. in the radio-TV service community. arranged as fins to permit ai r cooling. For the firs! year or so of use, the forward The dark side of selenium rectifiers is Otber Metallic Rectifiers volta e drop increases as the copper oxide their instability over time and their ten­ g Magnesium-copper sulphide rectifiers rectifiers age, but once aged, they are very dency to wear-out with age and high tem­ were seen as a possible alternative to sde­ stable. peratures. For general-purpose bulk recti­ fication, things like unStable reverse cur­ nium rectifiers. Several problems have kept this type from gaining a Along with Tungar gas rectifiers, copper rents arc not a problem. However, the fo r­ popularity: oxide rectifiers were heavily used in the ward voltage drop increases over time, and significant hysteresis in the forward volt­ age and current with applied AC voltage, high reverse current, maximum TC"Verse Typical5eknium Recrifim voltage of about 5 voltS per cdl, and a much shoner life-time than selenium.

TItanium dioxide rectifiers, made by applying bismuth to a larer of titanium di oxide built up on metallic titanium, were devdo�d by Banelle Memorial Institute in an effort to create very high temperature rectifiers. They could func­ tion at well over 300QC, and up to a point, their characteristics get better with higher t"emperature. They have fairly high leakage current, and a maximum reverse voltage of from 5 ro 15 volts per cell.

6V6 Shootout, \ Tube Headphone Preamp project, and More.

VACUUM TUB E VALLEY ISSUE 9 • METALL C R E C T F E R S

Although not consider� in th� sam� for sel�nium. In cases wher� the DC volt­ Th�re has been some concern about family as sel�nium rectifi�rs today. g�rma­ ag� is r�gulated or can b� adjusted, such as whether thc original s�l�nium r�ctifi�r can nium and silicon reccifiers were grouped with the bias r�ctifier in Dynaco power be k�pt in th� circuit. If you simply wir� with metallic rectifiers in the 19505. amps. thcr� is no problem, and no othet silicon rectifiers across the terminals of a Germanium alloy-junction recdfiers were pr�cautions ar� n��dcd. In cases where selenium rectifier, virtually all the forward th� first comm�rcial pow�r rectifiers built there is no regulation and the DC vohag� current will flow through the silicon, usin g the single-crystal technology devel­ is critical, such as in DC filam�nt sup­ bypassni g th� selenium. This bypassing op�d for transistors. and were firS( avail­ plies, s�ri�s resistance should b� added to techniqu� is convenient, since the old r�c­ abl� about 1950. Gcrmanium rectifiers bring the DC voltage to the correct value. tifier acts as a terminal suip for the silicon hav� a very low forward volta e drop - This value should be d�termined from the rectifiers. Howev�r, ther� have b�en g about .2 to .4 volts, high br�akdown volt­ manufilctur�r's documentation, sinc� th� reports of seleniums burning-out due to ag� (up to 300 volts), and reasonably low \'alu� m�asur� with th� existing selenium rev�rs� current, so for saf�ty. the sel�nium reverse I�akag� current. Their main limita­ rectifier is likely to b� low. If [h�r� is no should nOt be connected to the ci rcuit. tions are: limitcd high temperature opera­ documentation, an estimate can he made tion of 85°C maximum, and the n�ed fo r based on the circuit usage. For example, Using the techniques described above, strict hermetic sealing. G�rmanium power tube filam�nt supplies ar� generally multi­ you can maintain equipment using metal­ rectifiers w�r� used. by industry and th� ples of 6.3 volts. Many pre-amps that use lic rectifiers ind�finitdy. military, but wcre too expensive for con­ low plat�-current tubes, such as 12AX7s, Bibliography sum�r use. will run th� filaments at lower voltages (from 5.0 to 6.0 volts) to r�duc� noise and 1. Metallic Rectifier and CryStal The first silicon power r�cdfiers were incr�as� lif�. Diod�s, T. Comi, John F. Rider, N�w alloy-junction types. similar in consuuc­ Yo rk, 1958. tion to germanium rectifiers, and were Th� best way to pick a s�ries dropping comm�rcially available in the �arly 1950s. resistor is by cut-and-try, since there is no 2. SeI�ction and Application of M�taIlic R�ctifiers, S. P. Jac on, McGraw Hill, Th�y improved upon germanium rectifi�rs easy analytical way 10 charact�ri7.e the cur­ N�w Yo rk, 19S7. Ks by having extr�mely low leakage, high rent pulses in a capacitor-input rectifi�r maximum opcr.l[ing t�mperature 50°C) ci rcuit. Either have a handful oflow­ o 3. Pow�r R�ctifi�rs with Not�s on and breakdown vohages up to 1000 volts, ohmage power resistors or have a power Con\'�rting Machin�ry, J. Rosslyn, although they have slightly higher fo rward rheostat, and substitlLt� resistors until the George Newnes Ltd, London, 1941. voltage drop (approximately. . 7V). In DC voltage is correct. Make sure th� AC 1956, commercial diffused-junccion sili­ power line voltag� is al a known nominal 4. Tc.ning and Replacin� Selenium , con rectifiers became available, bringing \":t lue (generally 120 volts in North Rectifi�rs D. Schoo, A"nque RAdio Sepf. 1997, pp. 18-23. better control of charact�ri$tics and much America) wh�n doing this. Pick a power Classified, bctter elcctrical ruggedness. Later, silicon­ rating so that rh� resistor does not run 100 dioxide passivation was added to allow hot. As an example, when the selenium packaging in non-hermetic packages. This bridge r�ctifier in a Fish�r SOOC rec�iver is basically th� sam� construction as the was replaced, it was ubiquitous 1 N4000-s�ri�s of r�ctifi�rs so found that a 4.70 5 watt r------'-----::------,;=::------, common today. resistOr was need�d to bring the voltage within Dealing with Selenium Rectifiers spec. In electronic equipment that uses metal· The voltage rating of a lie rectifi�rs, selenium is by filr the most replac�ment rectifier can common, so from this point on, the dis­ be determined either by cussion will fo cus on selenium. When counting the plates in the re fu rbishin a piece of vintage equipment g selenium rectifi�r. or by that uses sel� nium rectifi�rs, decision a the AC vo1tag� in needs to be made on whether to stay with used. [h� circuil. Us ing the sel�nium, or to replace with silicon types. plate method, allocat� 25 If historical accuracy is desir�d and the volts per plate (between equipment is not hcavily used, th�n Stay­ terminals), and multiply ing with selenium makes sens�. the If by 2 as a safety filctor. ri i o g nal rectifiers are weak, as det�rmined Using th� AC voltage by low DC OutpUt voltage, then they can method, take the AC be replaced by either a scl�nium rectifier vo lta � presen{�d to the removed from other equipment or by an g rec[ifi�r, and multiply by unused. N.O.S. r�placement. On the other 2.83 for half-wav� and hand, if JUSt fu nctionality and reliability c�nter-tapp�d full-wave are desircd, thcn the seleniums should be circuits or by 1.41 for replaced by silicon recti �rs. Howev�r, sili­ fi full-wav� bridge circuits. con types cannot JUSt be substituted with­ Then take this resulting OUt som� thought on th�ir usage in the Introducing peak voltage, and multi- circuit. The Ultimate Dynamic ply it by I.S to 2 to give a safety filctOr. Remember, Headpbone Amplifier. Because of the lower voltage drop of sil­ you can always use a icon recrificTS, the rectified DC OUtpUt Hi-Fi Show 98 Westin Hotel suite 976 high�r-Iha -necessary voltage will rise when silicon is subStituted ? (213) 467-4300 voltage raong.

VACUUM TUB E VALLEY ISSUE 9 • It's Like Music to Yo ur Ears ..•

Amaudio tubesperex are back and they'reBugle better than Boy everl

When it comes to selecting premium audio tubes for your amplifier, accept no less than the best, Amperex Bugle Boy! Amperex Bugle Boy tubes are burned in under full load with all vOllages applied for 24 hours before being tested for noise mlcrophonics. The aging racks a used are from the original Amperex production line built in Holland decades ago.

Complete test results are supplied with each tube, Including plate current, screen current, filament current, and total harmonic distortion (THO). The THD measurement is performed using one of the flnest spectrum analyzers available - the Hewlett Packard 3561 A. Matching in pairs, quartets octets is available for all a tube types.

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Model Description Assembled Kit Chrome each each add-on A·I Amplifier 10 Watt Mono Block, 2 x EL·84 $ 299 $ 229 $ 60 p.p A·2 Amplifier 10 Watt Stereo, 4 x EL-84 P-P $ 435 $ 349 $ 80

A·4 Amplifier 30 Watt Stero, 4 x EL·34 $ 559 $449 $ 95 p.p A·8 Amplifier 80 Watt Mono Block, 2 x 6146B $ 1195 $ 995 $ 120 p.p PP·I Phono Pre-Amp, Stereo with Gain control, 40dB gain $ 439 $ 329 $ 50

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• a c a e • I p k 9

•

0 music lovers spmhr ­ Th is is 'he is brought doser 10 lis/mer tilt musical even/ throllgh rhe r,.;illdo'W

of lhe A/ix-AIINt Th ere is (I If. SI!{/m/ess iNlegrolioN of Ihe voice of Ihe speaker 'if:hich leoves Ihe

ill/passion of (I sillgle perjecl (ltiuer · 110 porI of Ihe sptrlrlll1l is fot )ol'td ooer ollolher. has Ihe /1 agilil)' 10 accllro/e�\' ,-ecrtolt lite Irtlllsielll 1101llre of 0 pi/lIJo,

a plllcked slrillg or IJ slmck ins/mlllelll. AI Ihe sOllletime, il lac/:s 011.1' sigil of slored el/ergy of

its Ort:1I so IlrallHt 1101llrol modllloted dero.l' of 011 illslmmmt sillks illlo silml blod:llfif ill proper time. Allollrer impol1/IIJI rh/mlC/enSlic is Ihol the spftlktr

Jleilh�r di miNishes Nor exaggemles Iht scale siz-I! of a IIIl1sical tIlltl dB $PL 2.83\'/ I meter sensitivity in a true illslmmflll or uoice. This is 0 rare 96 transducer utilizing a patemed. pure first order. compli­ nccomplishlllflll ill n speaker mentary symmetry crosso\"cr. Suitable for solid state amps s. l'sum, The bliJJgs ro 300WPC: or experience the magic of uncompromised Alix�A7JlJf 1/ performance with the SE 300B. The stable resistive load Ihe pefor rmallce/0 Ihe Its/eller alld that the Alix-Annc 11 presentS ro a single ended amplifier l!tell disapp ears so Ihol Ihi results in a near perfect match. CONllec/ioN of lis/flier to Designed for operation on or i pressure zone, n the the wall pelforming ar/is/ is direct. this wall-mounted speaker uses zero floor space.

Dimensions: 37" x 14.25" x 3.875" 11'0Iter /JoL'ies...Ihe.LnsL Constructed of beautiful, solid, non-endangered hard Foetory woods.

Manufactured cxCIU:>'VHly by AMERICAN APPLIED ACOUSTICS ..,nder licen.. From Americon Po_er ond Ughl, Inc. Dealer IlIquiries im;i/ed Phone: 916.666.1 873 SlIggt'Sled Relflil Price per pair $3.995.00 Fox: 916.666.6272 , • A LE E 0 REB RThe legendary British made Enlarged, heavy gauge figured glass KT66 is one of the most boUle handles higher temperatures, famous tubes of all time. In improving performance at higher the 60's it powered other power levels. British legends like Quad Hi

Extra thick premium quality star mica Fi amps and the first Marshall spacers (top and Bottom) impl'O\'es guitar amps. This tube was performance stability and reduces the sound of Eric Clapton on adverse microphonics. the classic John Mayall Bluesbreakers album. Precisely tensioned filaments for hellet mechanical stability and reduced adverse microphonics. If you can even find an orig­ inal KT66 today, they'll set Oeep swaged heavy grid rods you back up to $300 made from pure copper provide apiece. improved mechanical support for grid windings. Groove Tubes has given Stile nickel beam new life to this legend, trode concentratesfO��;;':I�I the ��1 creating our own tooling to now predsely on the plate manufacture it again. We improved power output. were able to keep the Heavy duty plates made from a sound and improve on the special alloy are stiffened with tube in satisfying ways. ridges and coated for strength and durability. With our precision tooling Enlarged phenolic base provides and modern manufacturing excellent contact with glass envelope processes, we consistently hold and insulation, preventing shorting tolerances the 60's original could between critical components. never attain. Insights from our research allows us to control All specifications equal or musical parameters no other exceed the original Genelex Gold tube maker even knows about. lion standards. KT66 Groove Tubes is offering Periormance Matched Duets of the GT-KT66R @ $120 (U.S. retail price). IHE GI-KIBB.. . Groove Tubes The American Tu be Company, since 1979. 12866 Foothill Blvd., Sylmar California 91342 USA To l: (818) 361 -4500 • Fax: (818) 365-9884 • www.groovotubes.com

• �urbe!,or s of& "(!Classic" mransformers (fnclosures

Single Ended, Push-Pul/ and Potted Tu be Output Filter Chokes Tra nsformers

Aluminum & Steel Chassis and Diecast Aluminum Enclosures

Open & Enclosed Filament Tra nsformers High Vo ltage Plate Tra nsformers

Contact us for a free catalog & list of stocking distributors HAMMOND

4700 Genesee st. - Cheektowaga, NY 14225 USA Phone: (716) 631-5700 Fax: (716) 631-1 156 394 Edinburgh Rd., N. - Guelph, Ontario N1H 1E5 Canada Phone: (519) 822-2960 Fax: (519) 822-0715 www.hammondmfg.com e are a proud dealer of We s"rtf Elechic Audio Products. The current production 3008 is now in stock. W Electron Valve stocks a wide array of NOS Vintage Audio Tubes like Mullard ElJ4, ReA 2A3, and Mullard 5AR4. We also have a good stock of Old Production Yoursource for hard to find Western Electric tubes such as 205B1D, 252A, 274B, 300B and many others. Vintaae Audio Tubes Electron Valve carries Precision Tested Ram Labs Reference Tubes. These tubes are computer tested, graded and and Quality Vacuum Tube matched to ultra high specifications predetermined by Roger A, Audio (omponents Modjeski. We also carry the Music Reference 1i1�RM-IO (Push-Pull 6BQ5, 35WlSide) Stereo Amplifier and the j!llild StilI! IIr I!�!ilt 1t!1I I Illkulll ll llr ,rllllll! Music Reference RM-200 (PUSh-Pull 6550, WW'!\'.eledron-valve.com • Email: infQ@eletlron·vah I'hooe:901-382-9955 . Fax: 901-382-9956 -e.com IOOWlS ide) Stereo Amplifier. • Back Issues, Books, Goodies, & Subscriptions

VIVllSpring 1995 S8 US-SIOFtJrtign Vintage Hi-Fi Spotter's Guide-Volume I Vinrllge Dynaco Tube Equipment - 1955-77 Over 450 photos & 5p«ifiC:llions of tube :l.l.ldio gear HislOry and "\eli!ing of the 12AX7/ECCll3 dual triod\" from the Golden Age of Hi Fi. 86 pp. $18.95 Tube Testing Methods t Early AmplifICation and Amps Vintage Hi-Fi Spotter's Guide Vo lume 2 vrv 12 FaU 1995 512 US- $15 F/lrYl'gn Vol ume 2 W\'crsC'quipmem nOI [isleC$ and Listening Tesl.$ 1950$ home hi fieta. Over 80 clas$ic audio amps, pre­ Vintage Booluhclf Speakers 1955-1965 amps tuners, are $hown. This video is professionally pro- Enly FM Bro.1dcasring History duced. 34 min VHS NTSC $25.00 HK Galion [ & 11 Amplifier History and Mods The Ultimate Tube Substitution Guide VlVI5 Fall l996 SlZ US -S15Fflnign No tube eka:ronies emhwim should be "ithoul this The Ultimate FM Tuner Shoot Out book. Over 10,000 tubes are listedon 240 Resin clud­ an Red Bank Guided Missle Tubc$for Hi-Fi ing: audio, nldio, tnll15mirring, and special. Features The Birth of Ihe Mar:mtz lOB audio tubes eerion withtu be eval uation. $29.95 Choosing Rectifier Tu bes foryour GuitarAmplifier Va cuum Tube Va lley T-Shiru VlVI6 Winter 1997 $12 US -S15FQnign . Two Iii. · .... Fisher 500 - History, Models and Restoration 5ryles 10 Choose Froml .� � , MarcbingTubes -"BigTone" A Tribute to Avery Fisher by the Fisher Doctor A)VJV 6550 and KTSS Hinory, lyPes and Listening TestS 1 $ided available in several rolors. Loftin-White Amplifia History by A1an Douglas Ta n, &.a Foam Green, and Burgundy $15.00 XLo nly

vrv SunburslTube Shirtwith 2-color black & orange VTV #7 Summer 1997 $IZ US- $15 Fflnign B) art;upictured largeplus 2-color RCA rube 6DJ8 & Fr:une Grid Tubes + Usu:ning lars diagram I§t:fn on back. (white or $20.00 A1t« 1950s Theater Amps and Modifications ...-...¥8o�.:£ie:..:.�1ty-- exploded yi cw gray) XLo nly The Great Voice - Thc Peter Jensen SlOry -- '- Computing with Tubes - The Savage An ___" 417A15842 VJV Politically Corm:t umper Sticlr:er Uncle Eric's Tube Dumpster - B U.e aGa !ransl.to Ta [wo-rolor waterproof vinyl 2'I'I 10· S15 Fflnip VIV#8 Fall 1997 SI2 US - S Jail Sent POSI_paid, 53.50 - 54.50 Foreign fIN, ...... US EL84 HislOry, Types & Listeninglesu \SiIw. RCA Tube Mfg at H�rrison, New Jersey Quotes from VTV Subscribers: 200 OTL w.m Amp Project by Allan Kimmel "'TheDelt ovdio mog on the planet." "Clearly written 9reat photographl." with 300B Limning 'Iars: NOS lnd Vinlage Types -A wealth vacuum - -vTY with authority and truth... " Bruce Moon:Tube Audio Pioneer of ruDeinformo tioo. reads

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