Tm

t

m9 9 averflegy â>pping Y9eg 'fithfjq D e &DI'lige kjl eYfelit,É,;',Dbirrhà.1 $(9J0

04 14g ... 1'131g Sound!

M (D ntims,D-,;rà 30 0 Watts of Badass Bass

5--ifIrcjAm WdElno MbmPd Great Tube Sound on a Budget

Ylr ihEimçjQh ®JmuSi Restoration of an Altec 287 W

• N r.. ':i:* '• 1": - E D I T O R ' S P A G E A N D I N D U S T R Y N E W S

El Nino washed out the vintage elec- VTV In The News - Again! tronics flea market on Saturday, a crowd VT V Issue # 9 of almost 500 new and familiar tube As a result of our Tube Enthusiast's Table of Contents: enthusiasts showed up for our tube Weekend, most of the VTV editors were trade show and display show. We also interviewed by the San Francisco presented Tube School III with John Chronicle newspaper for a major article Atwood, VTV Tech Editor, as class that appeared in the February 7, 1998 Legacy of the 50 Wafter 3 leader and Evan Aurand with Terry Business Section. VTV's Tech Editor, Buddingh handling the Amp John Atwood, was pictured on the front Transmitting Tube Test Amp 7 School. page of the article.

Dumpster: 2C51/5670 10 New York Tube School: Fall 1998 Business Week Magazine also got into the act and was interested in the "tube If we get at least 50 pre-registered Listening to SE 211/8455.-11 audio" phenomenon. They interviewed sign-ups (by 8/15/98), VTV will present yours truly and took 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 First Tube PCs 18 eight hour class covering the basics of tube electronics, tube amp circuit theo- Call for Articles Winter 1998 CES Report 21 ry, tube testing and grading, repair & VTV is always seeking quality articles troubleshooting techniques, equipment on audio and electronics history, good Vintage Audio in Japan 22 mods & upgrades and listening tests. sounding tube hi-fi projects, pro-audio Tube School is designed for attendees at history and related subjects. We accept Analyzers II 25 the beginner to intermediate level of skill. articles only in simple text format on VTV will also present a four hour 3-1/2 inch floppies. Any photos should Altec 287 W 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 Atwood, MSEE and VTV values listed. We do pay authors for their work if it is published in VTV. Metallic 32 Technical Editor, is Tube School class leader. John has over 20 years experi- Share your knowledge and passion about tubes with the world community Advertiser Section 35 ence in amp design and repair. Additional speakers will include: of tube enthusiasts-write for VTV. Al Pugliesi, The Fisher Doctor; Charles VTV Subscription Price Increase Kittleson, VTV Editor and other nota- Tube School Update bles in the field of tube electronics. Due to increased rents, postage and printing costs, VTV is raising the sub- VTV has presented two Tube Schools 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 II in Tempe, Arizona with magazine. Current issue news stand and $179 at the door. Price includes all distributor cost is $9.00/issue, US sub- the assistance of Antique Electronic class materials in a binder plus coffee Supply. For the first time we included a scription rate is now 836/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, telephone num- tive with VTV #9. tion, Ritchie Fleigler, VP of Marketing ber, whether you want the hi-fi or guitar for Fender Musical Instruments, gave a amp class and credit card information to Changes in VTV #9 talk on the state of tube guitar amps at reserve your seat in class. If we do not Fender Musical Instruments. get the required number of class sign ups Due to space constraints Part 2 of the Bruce Moore interview and the 572-3 In February, VTV sponsored the first by August 15, 1998, your payment will be refunded promptly. push-pull project will not be annual Bay Area Tube Enthusiast's in this issue. They will be in VTV #10. Weekend. Even though the rains of

EDITORIAL STAFF Copyriet 1998 Vacuum Tube Valley is published qua rter- TM Vacuum Tube Valley' and Big Tone ly for electronic enthusiasts interested in the colorful past, present and future of vacuum Charles Kittleson - Editor and Publisher No part of this publication may be reprinted or otherwise reproduced without written tube electronics. John Atwood - Technical Editor permission of the publisher. Subscription US$36.00/year (4 issues Eric Barbour - Staff Editor Send circulation and editorial $43/Canada and $66/Asia, $56 Europe correspondence to: Terry Buddingh - Guitar Editor Cash, US Bank Check, or Credit Cards Vacuum Tube Valley are accepted for payment Steve Parr - Art Director 1095 E Duane Ave., Suite 106 Julie R Werner - Copy Editor Sunnyvale, CA 94086 USA Phone - (650) 654 - 2065 e-mail @vacuumtube.corn FAX - (650) 654 - 2065 Website - www.vacuumtube.com ISSN # 1095-4805

V A C U U M T U B E V A L L E Y IS S U E 9 L E G A C Y O F T H E 5 0 W A T T E R

Not many other types were so widely Legacy of the 50 Watter: copied and modified. A smattering of ver- sions include the 203H for medical diathermy, with plate and grid caps; 303A was the United Electronics version; 211 & 845 Taylor's T-125 was a 150w version with mu of 20 and plate and grid caps; Taylor's By Eric Barbour 303C/HD203A had a plate cap and mu of 25; 295A was the Western Electric ver- 4AZ © 1998 All Rights Reserved sion from 1933; T-203Z was a Taylor ver- sion with mu of 85; and there were too Intro large transmitting tubes in mass produc- many other versions from other firms to tion. The plain-tungsten 203 was also list 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 PG132 again, a tube family in common use today and HW15. sprang from a line of industrial triodes, and became audio gold by sheer accident Unlike most and random chance. other power tubes of the 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 Pliotron" 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 frames Introduced in March 1921 by RCA and and attached to made by GE, for use in AM radio trans- their circuits mitters, it had a mu of 25 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

Early 845 3211 cartons

in the very early days of radio broadcast- stubby pins, originally ing. Note: WE's 203 series of tubes were developed by Western much smaller than industry-standard 203 Electric and often called types and not compatible. the "jumbo," became a standard for power tri- Eventually this led to the 211. It was odes. developed by Western Electric from their experimental series G, with the first ver- Thorium was a big sion 211A completed in late 1921, then improvement. The UV- copied in late 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- Westinghouse, was one tric heating and audio modulators. A dull of the first power tubes and pedestrian tube for dull everyday to be introduced with a jobs. (If a radio engineer of the 1920s thoriated filament. Its lived to see what old 211s are selling for dissipation, rated at today, he would probably die laughing.) 100W, made it popular. 211 types were widely made by other Later it was cloned by firms, as they caught on in mundane Amperex, Deforest, GE, industrial and medical applications. Sylvania and Taylor. 1921 RC,',1 Type 203 and WE 211E

V AC U U M T U B E V ALLE Y ISSUE 9

3 L E G A C Y O F T H E 5 0 W A T T E R

with a plate cap; 211H 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 low-capacitance version for the low end of the VHF band; and RCA's 838 was a variable-high-mu version for zero-bias 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 variable high-mu grids and were intended for Class B AF modulators. It also led to 810 types and to a long series of Taylor 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 UV845. In an era when transmit- ting triodes were headed toward high-mu WE 211D, WE211E r?nd WE276A design and grounded-grid or Class B operation, the UV845 was an aberration: Western Electric's versions started with Some other versions of the 211 include a 75-watt power triode with a mu of 4.8. the 211A ; the 211B, C and D were just the Western Electric 242A, used in WE's Later it was up-rated to 100 watts. the same tube with different grades of fil- model 80A audio amp; 242B and C were Ridiculously archaic and difficult to ament. 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 theater amplifier. A cially the C, which found use in the D- its continued use in older RCA BTA- pair of small nichrome-wire 90684 broadcast monitor amp; the WE series transmitters as the audio modulator were installed in the filament circuit, 261A was used in early WE AM trans- final amp, in a Class A push-pull pair. inside the actual tube, to help stabilize it mitters, while the WE 276A was a 100w- Such transmitters were often pressed into at high frequencies. This makes old dissipation version; 214A, D and E were service after World War II 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 214E and programming. Millions of Americans

Early and laki RCA 211s

V AC U U M T UBE V ALLE Y ISSUE

4 L E G A C Y 0 F T H E 5 0 W AT TE R

.: > rN =

,..e , L' ' "..-

.M e a a a el 2

DO

C..) 1 ' .., § ‘-• - - a •

S 1 I Î a S

s-

L I- • J J 1.1 8 4 d 1 î 1 = R•<

— -- Z e e ru m cll OVT 1 eà e '6 -4"-L 1 i r E 0 E JA'NUARY .41.9... d.-- 7‘,50R51 .< u< e e z .-.., . 11

. . J. 1 .. i ....-.

>.;-,--,

--.c \ --.---, r ...... --„-,--,L , '1. 2000 ,,..s tl -;-'f 1 ---r—_ I1 I,

, . g e./ =2 q S. <- ika. Iii, -, a 1.5c? ,----, SS

ú í VOLTAGE '"' ATE PL d II I

hi it > "----- z. — — Z ;7. Q 5 . . I ll EE el = < -H 1E I Ii iiit. I X M i e e P o ZI o ZZZ d à . g z e . I ndlelb11111, 3 ,1: 2 o à

1. 1

aC < ca u Z

u SI • I IL"' _ 1,M I

• :I /--, SI e / i . .

E 9 , o

V ACU U M T UBE V ALLEY ISSUE 9

5 L E G A C Y O F T H E 50 W A T T E R

use in AM broadcast Today modulators. There were other manufac- Simply compiling a list of all the firms turer's designations that made 211s 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-watter tubes in their variegated 211. Its mu was too forms, in the 21st century we are down low to make it suit- to two manufacturers: a Chinese factory, able for RF-heating and Richardson Electronics in Illinois. power oscillators, The Beijing "Sino" factory produces and any continued generic clones of the later GE 211/VT- manufacture was just 4C and the late RCA 845, both with to keep pre-1950 graphite plates and aluminum-shell bases. AIVI transmitters Richardson makes an 845, allegedly on retubed. the original RCA tooling, in small quan- tities and selling for a high price under High mu was the the Cetron label. Manufacture of later overwhelming trend relatives, such as the 805 and 810, con- after the war, and tinues in China and at Richardson. grounded-grid RF were the Although the "true" 50-watter types have been reduced to two specialty manu- last frontier for glass triodes—power facturers serving the high-end audio mar- ket, there is a similar tube from Russia: and pen- the Ulyanov GM-70. Its basing is unique GE JAN 211 & GE tjpe VT-4C todes elbowed them and its mu is about 7, yet in many out of most other were exposed to R&B and gospel music applications. The worm turned in the respects it is amazingly similar to the 211. via the smooth sounds of push-pull 845s, This triode, made since the 1940s, is lit- 1980s, and the last laugh is on the high- driven by interstage , with no tle-known outside of the Russian elec- mu family. For although the 811A, 572B, negative feedback. Altec, RCA and WE tronics industry. 3-500Z and other high-mu types contin- also used the 845 in a few theater amps ue to be popular in RF applications, the during the 1930s and 1940s.. Outro large, crude 845 has become nearly a reli- Western Electric's 284 series was very gious object to neurotic audiophiles, So, it appears that the 50-watter 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 W WII surplus VT-4C for as little as $4.

Bibliography

1. 70 Years of Radio Tubes and Valves, John Stokes (Vestal Press, Vestal, NY, third edition, 1992), pp. 127-132.

2. Transmitting Tube Catalog and Guide, Taylor Tubes, Inc., 1937.

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

4. Saga of The Vacuum Tube, Gerald E J. Tyne (Howard W Sams Publishing Co, Indianapolis IN, 1977), p. 150, 151, 287, 288.

Many thanks to Lauren Peckham of the Antique Wireless Association, Al Jones of the Transmitting Tube Museum, and Brother Pat Dowd for their invaluable assistance with the historical background. WE 284 er Late 1930s Sylvania 845

V A C U U M T U B E V A L L E Y IS S U E 9

6 T RA NS MI TTI N G T U B E T ES T A M P

The driver circuit is only meant for dri- A Transmitting Tube ving tubes in the negative-grid region (no grid current). This is the most common mode for medium and low mu triode out- Test Amp put tubes. By adding a strong cathode follower, say a triode-connected EL34 or 6550, positive grid operation (class A2) of By John Atwood © 1998 All Rights Reserved the output tube is possible, opening up the amp for use with high-mu tubes such as the 838, 811A, and SV572-160.

Running the 6B4G filament on DC is essential, since AC causes intolerable hum. Testing the audio performance of power lated DC filament supply, with its voltage A simple solid-state supply with choke fil- tubes with plate voltages higher than 500 adjusted by a desk-top Variac. The driver tering is used. The 0.6 ohm power resistor volts becomes more complex than simply stage and bias supply were mounted 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 Transmitting tubes also come with a vari- and a filamentary triode without feedback ety of socket types and filament voltages. gives a good low-impedance drive with To help us evaluate transmitting tubes, a decent frequency response and distortion. single-channel (mono) test breadboard The 6J7 pentode may look unfamiliar to was built with a large degree of flexibility tube purists, but the older low-transcon- in audio testing 211-class transmitting ductance types can sound very good. The tubes. In addition to being a good "test- 6B4G allows a low 10K plate resistor with bed," it turns out that with 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-quality 600 volt power supply is used. This may single-ended power amp. seem high compared to the 325 volt maxi- mum rating, but keep in mind that in a CAUTION: The amplifier described in transformer-coupled amplifier, which this this article is intended to be used only rating was meant for, the plate can have for testing components, and has deadly voltage peaks twice the B -i- supply. Used as driver stage is obtained by using a stan- high-voltage points exposed! Ify ou want a resistance-coupled amplifier, the 6B4G dard radio-type power transformer run- to use the circuit for general purpose lis- runs conservatively in this application. ning into a voltage doubler. The 6AX4GT tening, it needs to be packaged so that While initially designed for driving just damper tube rectifiers give a nice slow all high-voltage points are safely the 211-type tubes, the driver has enough turn-on. The 6AX4GT is abundantly enclosed! head-room so that it can drive 845s. The available in North America as a surplus regulated bias is not enough for the low TV tube. Test Amp Design mu of 845s, but simply pulling the OD3 The high voltage for the output tubes is out of its socket allowed the bias to rise Being a "one-off" design, the 211 test run through a 0-100 mA meter mounted high enough for our tests. amp was built around components on in an old sloping "meter" box. Also in the hand. Key to the amp is a good, high- quality high voltage power supply. A SE Transmitting Tube Test Amplifier Fluke 3010 precision high voltage supply had recently been picked up at a ham radio swap. Its maximum ratings are 1011 volts and 500 mA. It would have been better to go up to 1250 volts (the maximum rating of 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 construction was used, with high-voltages enclosed where possi- ble. Three tube sockets were ever installed, accommodating the jumbo four-pin 211- types (203, 211, 838, 845, etc.), the regu- lar 4-pin types (SV811, SV572), 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 nuts were used to attach to the transformer under test. A separate wood breadboard held an unregu-

V AC U U M T U B E V A L L E Y IS S U E 9

7 T RA NS MITTI N G T U B E T ES T A M P

Table 1 - Transformer Tests 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/10K/211SE 15852 33.9KHz, w/peak at 72.2KHz supply and plate current meter mentioned above, VOMs and DV1VIs were used to Bartolucci #28 24952 19.3KHz, w/peak at 53.9KHz measure grid voltage, filament voltage, and AC grid drive voltage.

Electra-Print KL1OKB-B 12212 28.11(Hz, w/peak at 79.0KHz Testing Philosophy

Tamura F-2013 29712 23.6KHz, no peak The goal of the transformer and trans- mitting tube testing was to run the unit Tango XE60-10 SNF 32212 92.2KHz, no peak in a similar environment to that of a real amp. However, due to fixed transformer The transformers were bench tested with a sine wave oscillator driving the transform- impedances and different characteristics ers through a 4.7K series resistors. The transformers were terminated into a non- between tubes, comparisons between dif- inductive 8 ohm load. Primary measurements were tried using the Freed ferently spec'd units (i.e.: 7K vs 10K or 1011 inductance , but there was difficulty in getting the bridge nulled. Later 211 vs 845) are not really valid since these investigation showed that at the highest inductance range needed to test these high- impedance transformers (> 100H), bad paper capacitors in the bridge prevented it have different optimum operating points. from nulling. The lower ranges used mica capacitors, which were OK. Even test However, comparisons of like units are equipment needs re-capping! (The bridge was recapped before any testing was done. Ed) valid. Also, both electrical tests and listen- ing tests would be done. As both forms of The Japanese transformers tested well, with good-looking 10KHz square wave these tests were carried out over a period response. Both the Electra-Print and Audio Note had reasonably good HF response, of several months, preferred operating although were somewhat lumpy. The Bartolucci had the worst HF response of the points changed, and will be noted in the transformers tested in this grouping- but interestingly sounded quite good! test results.

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 -52.4V 24.7V 5.0W 1.2% distortion and power output capability. 42.1V 13.5W 3% Unlike earlier tests published in VTV, a GE JAN CG-211 #1 used -n51.9V 24.6V 5.0W 1.05% standard harmonic distortion meter 43.2V 14.0W 3% (Sound Technology 1700B) was used, GE JAN CG-211 #2 new 7,53.9V 25.5V 5.0W 1.3% which captures all harmonics and noise. 43.5V 13.5W 3% To keep hum and noise problems down, a National 211 (China) #1 new 7,49.4V 25.3V 5.0W 1.2% 400 Hz high-pass filter in the analyzer 41.8V 11.2W 3% was engaged. The test signal was a 1KHz National 211 (China) #2 new -„50.2V 24.9V 5.0W 1.2% sine wave. Distortion tests were run at a 41.9V 11.2W 3% constant power output of 5 watts (6.32 United CUE 38111 used? 7,53.7V 24.2V 5.0W 1.1% Vrms across a 8 ohm load). This is higher 42.3V 14.3W 3% than the earlier VTV tests of 1 watt, but RCA 211 (prewar) #1 new 7,49.8V 24.0V 5.0W 1.25% the low distortion of these tubes allowed 40.3V 13.0W 3% noise to dominate at this low power level. 7,50.2V 23.6V 5.0W 1.25% RCA 211 (prewar) #2 new For power output tests, a distortion level 40.1V 13.0W 3% of 3% was arbitrarily picked as being well RCA VT-4C used -n50.9V 24.6V 5.0W 0.95% into for all the tubes. The 42.8V 13.5W 3% Electra-Print KL 10KB1OK output trans- WE 211D used 7,45.0V 23.8V 5.0W 1.35% former was used for these tests. The tubes 38.5V 11.0W 3% were run with a 1000V plate supply -n66.4V 30.0V 5.0W 1.35% Svetlana SV-811-10 new biased to 60 mA. 52.7V 14.5W 3% Svetlana SV-572-10 new -75.0V 32.0V 5.0W 2.1% The American tubes were remarkably 44.3V 9.2W 3% consistent in biasing, gain, and distortion, Russian GM-70 new ;-r91.8V 34.0V 5.0W 0.85% with the RCA VT-4C having the lowest 70.4V 22.0W 3% distortion at 5W. The Chinese 211s biased-up similarly to the American ones, (845 types were not tested because the test amp driver stage was designed specifically for 211s.) but had significantly lower maximum power. This could be explained if their characteristic curves were non-linearities ed in building high-voltage supplies is the box are a bypass capacitor (to help keep at the extremes. Several vintage WE Radio Amateur's Handbook, published high-frequency audio currents local to the 211Es (which have oxide-coated cathodes) yearly by the American Radio Relay amplifier) and a neon HV indicator. Since were tested, and many had unstable bias League (Newington, Conn., USA). a lab-type high voltage power supply was currents. Even the one finally used for the Editions from the 1960s and earlier are used for this project, a schematic for a test drifted a bit over time, whereas all the gold-mines of circuit and construction stand-alone HV supply was not devel- other thoriated-tungsten types were rock- oped. A good reference for those interest- information for the tube amp builder.

V AC U U M T UBE V ALLE Y ISSU E 9

8 T R A N S M I T T I N G T U B E T E S T A M P

Atma-SphereTM Amplifier Kits: Musically Authentic!

' M-60 Mk. H Kit $2295 (Pictured) I. 60 Watts of Tubed, OTL Purity

ce ...Breathe in and out

GM-70, Cciiv,i 8.15 bSvetiana like the music..." SV811-10 —Art Dudley solid. The SV-811-10 was a like a bit Listener, Spring '97 lower mu 211 — with slighter higher max- imum output power. The SV-572-10 was Authentic? Now there's a word rarely associated with audio gear. By a marginal performer, apparently due to definition "authentic" means genuine, pure, real, accurate. Exactly high distortion. The GM-70 was a killer tube, with low distortion and high power. the words describing the true note-by-note musical presentation of all This is to be expected from a lower mu Atma-Sphere audio gear. Musical authenticity begins with the designer. tube, which is why the 845s were not test- ed against the 211s. As with all these Ralph Karsten, our Chief Designer, could have easily built solid state tests, it should be noted that the statistical amps. Karsten, however, has the true desire to build genuinely accurate sampling of tubes is quite small, so be and purely transparent gear. Solid state cannot do it! Output careful not to draw major conclusions transformers cannot do it! So Karsten engineered and patented a totally from the data. Two old Western Electric new design combining, within each chassis, the musicality of two 211D tubes from the 1920s were tested. One would draw normal plate current for singled-ended tube amps with more authoritive bass power than a about 1 minute, then would slump to a single push/pull amp and with no output transfo rmer to snub the music. low value and distort heavily. Another used 211D (listed in Table 2) worked "...making fires in my soul... Y.> — Harvey Rosenberg well, but still had a somewhat variable Positive Feedback plate current. These old WE tubes use Vol. 6, No. 6 - April '97 oxide-coated filaments, compared to the thoriated-tungsten of all the other tubes * CALL NO W for information 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 difficulty to a higher level than conventional low-impedance amps: more dangerous voltages, expensive (frriNr . Atma-Sphere Music Systems. Inc. high-impedance output transformers, 511 e The OTL Leader, featuring Balanced Differential Design TM strange tube sockets, lots of heat. However, ® good amps using these tubes have a dis- 160 So. Wheeler, St. Paul, MN 55105 • Phone 612-690-2246 • Fax 612-699-1175 tinctive "big" sound - open, spacious, and www.atma-sphere.com dynamic - that is appealing. These big tri- odes are definitely the starting point for the "ultimate" tube amplifier. CORRECTION: VTV #8 - Page 12 This is the correct schematic for the Alan Kimmel OIL Amp. Do Not use the schematic shown in issue #8.

UPDATED FLOATING POWER SUPPLY +310V

D3 Howard Bardach CET 470K Changed Berme ProwderConnection m an limo ,___ sp e cialist +180V 13251 #0 Ventura Blvd. — Studio City, CA 91604 7500µF Bus. (818) 995-8648 Bridge 200V Fax. (818) 995-8647

Dl The Eclectic Audio/Video Service Center B— D1 - 04* 1N4007 (1000V, 1A)

V AC U U M T UBE V ALLE Y ISSUE 9 VTV #9 has an error on the transmitting tube amp voltage doubler power supply schematic on page 10. The 6AX4GT is wired wrong and must not short across the power transformer. John Atwood will be posting the corrected schematic in the next issue and on http://www.vacuumtube.com very soon. DO NOT BUILD THIS CIRCUIT WITH THE SCHEMATIC ON PAGE 10. T RANS MITTING T U B E T ES T A M P

40K 0.22 F 47 F 0.22 F — Tube Linder 600V T T 500V 3W 10K 5.0„ T Transformer 0.2 F 10W Test Under Test 600V Input 5 6B4 G 3 6J7 0.47 F 800V O utput Volume 00 5 8 Oh ms 2.0 F 100K, 400V 0.47 F 560 F 7 250V 100V

audio (LW U 0_032.0 0

L taper 330K "100K 1/ 01 3.9K 1500 43K 0.47 F T 5W 4.7 250mA + 250V I T 2000pF 2.0 F 6.3VDC ' 100V — 0.22 F --1--- 1200V o_u mo v 150 m A 35H, 15mA 0C3 5 /VR10 N E-51 —(61) 0-0 0 0.1 F O 30K Bias _ 2100V 100 F 2W 104507 350V T. 50K 0+ 2W 0-20 V

0.3 F o 1000V I " 15H, 75mA 3 '000 00 1

220VCT 6A X4 G T Suc 130500V F 130,00V F 270K 140 mA 1.5A SB 211 Test Amplifier 3

Power by John Atwood = 100 F 100 F 270K 6A X4 G T T350V 350V 120 VAC

m 5V 0.5 6J7 5W ,00000` 3A 100 PIV 0.035H to 6B4G Bridge T 0.755 filament 5.3v o 5A 2200 F 4700 F 25V 16V 6AX4 6AX4 47

appeared in the 1946-1960 period. device today may be the Fairchild 670 Occasionally used in early computers, the limiter, which can sell for up to $25,000. Uncle Eric's Dumpster premium version 5670 was once widely The 670 is unusual in that it uses two Type 2C51/5670 manufactured. It has controlled warmup gain control cells made from four 6386 and tight specifications on grid current, triodes in parallel. Since it is not used in By Eric Barbour noise and microphony. The 5670W was any other current application, and is out used extensively in 1950s military equip- of production, old stock can only go up in © 1998 IS ment. price. If you want to invest in an NOS tube, the 6386 looks like a good bet. The much scarcer 6385 is the Bendix "Red 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 ruggedized 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 triode is ly used as a gain-controlled cascode RF audio, as 1980s military-surplus 5670s of allegedly an RF only device. Yet our dis- amplifier. Although not really suited for good quality are readily available from tortion and listening tests seem to indicate hi-fi use, it has a special audio application. dealers, at absurdly low cost. So don't high linearity at typical 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 to 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- tions, many variations of the 2C51 GE 5 Stwi . V.yania Tuvo---Sol WE 3964 Syluahid 1980s 6386 2C51 2C51 5670

V AC U U M T UBE V ALLEY ISSUE 9

10 2 1 1 / 8 4 5 S E L I S T E N I N G T E S T S

845 gave much better integration to the VTV Listening Tests: sound and was very musical. Then we lis- tened to a United Electronics 38111 (mil- itary number) set at 980 volts and 60 ma. This tube sounded clear and integrated, 211/845s and 10K with a less aggressive presence than the GE VT-4s. The sound was well balanced with deep bass and excellent dynamics. SE Transformers With this transformer and setup, the United 38111 was the best overall sound- ing 211. By Charlie Kittleson © 1998 All Rights Reserved We obtained an early 1930's Western Electric 211D and noted the sound to be Over the last several months, the VTV impact on sound quality and perfor- similar to the RCA 845, except the overall staff and a number of local audio enthusi- mance. For the driver stage in Atwood's soundstage was a little smaller and the asts have been conducting listening and test amp, we noted 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 1940s Sylvania 6B4 had 211's and had good dimension and detail. 50-watt triode SE amplifiers have more a slightly congested midrange when com- The early 211s should be run conserva- power and realism than the majority of pared to the Tung-Sol 6B4s; these were tively (under 800 volts and 60 ma) to 300B amplifiers, based upon opinions cleaner and more detailed in the mids. In avoid any problems. addition, the metal RCA 6J7s were not as expressed during listening tests at VTV. The last tube we tried with the open sounding as the glass-type Sylvania For the audio enthusiast who simply must AudioNote 10K was the Ulyanov GM-70 have the most compelling sound, 211/845 6J7GTs, which were lighter and had more • with its huge carbon anode. It was set at amps are the way to go. Manufacturers 980 volts and 100 ma. This tube (mu 7) including AudioNote UK, Cary Audio, has a big, authoritative sound, but still Bel Canto, Wavac and many others are demonstrates intimate delicacy. The bass offering 211/845 SE amplifiers, but the is big, but is not as integrated as some of price typically starts at $3500 and up. the 211s and 845s in this test. With an The series of transmitting tube related optimized driver circuit, the GM-70 articles in this issue will give the reader & would make the ultimate heavy metal sin- home constructor detailed information, gle-ended amplifier. electrical test results and listening tests of new and vintage 211/845 types. The tube listening test was done in conjunction with our listening evaluations of new pro- duction 10K output transformers using John Atwood's test amp, described on page 7 of this issue. Additional equip- ment used in the test included an Elite Electronics CD player or the new Dynaco AudioNote UK #205 10K CDV-Pro tube CD player and either The AudioNote 205 transformer is a B&W DM-110 or Klipsch Chorus I eight beefy unit that is non-potted and uses the ohm . Program material con- standard copper windings. Other, higher sisted of well-recorded female vocals, con- priced 10K units are available from them temporary jazz and classical music includ- using superior materials, including silver ing Beethoven's Symphony #5. wire. The transformers were first tested Tubes were typically run at anywhere with a GE VT-4 (211) set at 980 volts from 760 to 1000 volts with plate current running 60 ma. With this combination, Bartolucci from 60-100ma. In addition, we also we noted very good bass response and a The Italians are at it again with three smooth upper treble range. Next, we auditioned the Ulyanov GM-70, a huge, 10K transformers from Bartolucci. These tried the AudioNote with a 1943 date low-mu thoriated tungsten transmitting handsome, potted units are all very musi- code RCA 211, with the same voltage set- tube from Russia. Note that this test does cal and will work very well with horn-type tings as above. This combination resulted not include all possible combinations of speaker systems. We listened to the in a similar sound to the VT-4, but with a tubes and transformers. This is because Model #29 10K unit with a 32 watt rat- little better midrange. we began to notice characteristics in tubes ing using the GE VT-4C tube. The bass that made us gravitate towards the better Next we tried a 1940s RCA 845 set at was big, solid and well controlled. Mid sounding ones later in the tests. There are 760 volts and 60 ma plate current. This frequencies were smooth, lush and rich other 10K SE transformers available on combination resulted in a clean, detailed sounding, extremely musical. Next we the market, but these were not made sound with incredible depth. The lower tried the Bartolucci #58 10K SE unit with available to us for this test. plate voltage was needed to keep the tube the United Electronics 38111. This com- bination gave a deep, convincing bass that In our listening tests at VTV, we have within biasing range. In addition, the was almost romantic sounding. The highs noted that several factors can have an mid-bass had much better presence. The

V A C U U M T UBE V A L L E Y IS S U E 9

11 2 1 1 / 8 4 5 S E L I S T E N I N G T E S T S

and the mids with this combination were ma. This combination with the Electra- very engaging and rich sounding. The Print was excellent, very musical, but did- highs were not as extended as the other n't have as much deep bass the RCA 845. transformers in this test, but this could be Note that the GM-70 is extremely difficult a plus for those with sensitive horn speak- to get and is not available from any Russian ers who don't want harsh highs. Overall, tube vendors at the current time. the Bartoluccis were very easy to listen to, but are not for the extreme high frequen- cy detail freak. For those who want a romantic, "European" sound, go with the Bartolucci 10K units.

made and has excellent characteristics. With the GE VT-4C, the sound was refined and polite, almost courteous. Even though the unit was sweet and dynamic, the soundstage seemed smaller than many of the other transformers in this test. The Tango had excellent high frequency measurements. Sound improved with better bass, detail and bal- Tamura ance using the 38111, RCA 211, RCA We sampled the beautiful and huge 845 and Cetron 845s. Tamura F-2013 10K SE unit. Using the Conclusions GE VT-4C, this transformer had the deepest bass, clean and accurate mid-fre- After listening to all the 50 wafter fami- Electra-Print quencies and super-extended highs. ly transmitting tubes in this test, we came However, the pace and timing were a bit to some enlightened conclusions. The For this test, Jack sent us two versions slower than the AudioNote or the Electra GE-VT-4 is the most common NOS type of his KL1OKB, 10K 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 crisper, 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 can cost over frequency response than the first proto- 950 volts with 65ma plate current. This $300+ each! The United Electronics type we reviewed. Again, settings on out- combination was detailed with very clear 38111 is an excellent 211 type, but is put tubes were 980 volts and 60-ma plate sounding instruments and voice repro- even harder to find in any quantity than current, unless otherwise noted. The first duction. The bass response was extremely the RCA types. The glass tipped WE tube we tried with the Electra-Print was convincing and optimum. The next tube types as well as the 242 and 284 types are the GE VT-4 that exhibited a big sound, we tried was the SV572-10 which was extremely rare collector's items and can but was somewhat forward when com- powerful, clean sounding and had an low cost over $500+ each in NOS condition. pared to the lower mu 845s. This tube noise floor. The 572 did not have the Svetlana SV572 and SV811 types are has good attack, with super-extended power or bass response of the larger tubes. unique tubes that we know sound good in mids. Next came a 1974 vintage, Then came the United Electronics 38111. circuits optimized for them. American-made Cetron 845 that turned This combination was accurate, involving out to an excellent sounding tube (close and balanced sounding. The response The best buys are the Chinese-made to the RCA 845), very musical with a was smooth and very detailed with great 211s and 845s which can be purchased sparkly sound. The SV811-10 worked top end. Overall, a "real" sounding tube for under $50 each. The Chinese 211s well with the Electra-Print, giving clean, and transformer combination. Lastly, we had good mids, but the bass was softer balanced sound. The SV572-10 was sim- used the Cetron 845 that gave a super and highs thinner than the others in this ilar in sound, but did not put out as balanced sound with clean powerful test. However, these tubes have an much power in this setup. Then we tried punch. The Cetron with the Tamura is expected service life that is significantly the United Electronics 38111 with the very accurate and musical. The Tamura less than any of the American types. The Electra-Print; that resulted in a bigger has more of a hi-fi tilt, but in some best new production 845 is the bottom-end and a wider bandwidth. This speaker systems with sensitive horns, this Richardson-Cetron 845 that is currently "American" combination was a little for- characteristic might sound a little sizzly. being made at their facility in La Fox, ward sounding, but not harsh in any way. Overall, the Tamura appeared to be the Illinois. According to Richardson offi- Then came the RCA 211 which proved to best made and had the deepest low bass. cials, they have the original RCA tooling be musical and involving. This combina- and equipment for the 211 and 845 tion had good timing and sweet, seamless Tango 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 much longer than the Chinese types, into the socket and noted a similar per- in their tube electronics products. We are easier to source and come with a formance to the RCA 211, but with deep- sampled the Tango XE-60-10, 10K SE factory warranty. er bass. Then came the Ulyanov GM-70 unit. This transformer is beautiful, well that we ran full-tilt at 1000 volts and 120

V A C U U M T U B E V A L L E Y IS S U E 9

12 T H E A M P E G S V T

The B-15 Portaflex The Ampeg SVT: The move to Linden in February 1962 marked the beginning of the modern era—an era of change—for Ampeg. Their History and Variations need for growth was propelled by the suc- cess of their first true classic--the Jess Oliver designed B-15 Portaflex (intro- duced in 1960). It incorporated an innov- By Terry Buddingh © 1998 All Rights Reserved ative "flip-top" configuration which con- cealed the amplifier's chassis inside the closed-back speaker cabinet for safe trans- portation. This would eventually lead to the amazing Oliver amps with motorized Ampeg History audio electronics. (Many of his books electronics that would dramatically elevate were published by the notorious Hugo from their cabinets. (Truly a sight to In the late 1940s jazz bassist Everett Gernsback.) Eventually there were four Hull had a singular vision—to provide behold!) Over the years the B-15 would versions of the Ampeg Bassamp ranging go through many stages of design evolu- bass players with a quality means of from the 15" Jensen speaker equipped, amplification. He mounted a small micro- tion. The earliest versions were cathode- single-channel model 835, to the mon- biased and used point-to-point wiring on phone (made by Clevite) to the retractable strous 950C with three channels and two end-pin of his bass and called it an eyelet boards similar to Fender's (but nar- 15" speakers. In 1953 bassist/designer Jess rower). These first versions were excep- "Ampeg" (short for amplified-peg). Hull Oliver (a.k.a. Oliver Jespersen) joined the teamed with Stanley Michaels to design tionally sweet sounding, but not very Ampeg team and was instrumental in its loud. Later versions used fixed-bias and an accompanying bass amplifier, and growth from the small two-room factory together they formed the short-lived PC boards. My favorite is the B-15-N in Brooklyn to the 40,000-square-foot which employs three 6SL7s (I love their Michaels-Hull Company. In 1949 Hull modern facility in Linden, New Jersey. It and Michaels dissolved their partnership fat richness), a pair of 6L6s, and a 5AR4 was during this period that Ampeg began rectifier. Other versions use 5U4s or solid- and the Ampeg Company was officially to develop a reputation for quality by born. state rectifiers, 12AX7s, 7199s, and enlisting endorsements from esteemed 7027s. players like jazz virtuoso Oscar Pettiford. For historical perspective it's important The B-15 would become the industry to know that 's brilliant innovator To fully understand Ampeg it's neces- Lloyd Loar experimented with electrified standard for recording in the '60s. The sary to understand Everett Hull and Jess role of the electric bass was redefined by bass in the late '20s. Rickenbacher and Oliver. They were both professional Vega were selling electric upright basses the great James Jamerson, who played his bassists that regularly performed the stan- '62 Fender Precision bass through a B-15 and amps by the '30s and Leo Fender dard and jazz tunes of their day. They on many gigs and some recordings. To introduced his first Precision bass in '51 spent decades meticulously refining the clear-up a common misconception, how- and his first Bassman amp in '52. nuances of their craft. They felt it was ever, it should be noted that on most of their responsibility to protect and defend The first amplifiers produced by the the Motown hits recorded at the famous the music they loved from the "crude, new Ampeg Company were designed with "Hitsville USA" studio in Detroit, the loud, and vulgar" rock music that was, to the assistance of the great Norman bass and were recorded direct Crowhurst, who would become one of the their dismay, becoming increasingly popu- through a one-of-a-kind six-channel pre- lar. most prodigious authors in the field of amp made especially for Motown. Jamerson's contemporary at the Stan label—Donald "Duck" Dunn— amplified his '58 Precision bass with a B-15 as well. The deep blossoming bloom of the B-15's liquidly round and warm bottom, and exquisitely detailed, sweet and expressive midrange defined the very essence of great bass tone.

The B-15 sounded great in the record- ing studio, but as the '60s progressed— and the volume levels increased—it became apparent that a pair of 6L6s was not sufficient to keep pace with the 100 watt guitar amps that were gaining in popularity with the rock players of the day. If Ampeg was to keep pace with the times, a higher powered version of the B- 15 would soon be necessary.

The UNI Music Period Hull and Oliver would stubbornly resist the need to acknowledge the changing 1969-70 SVT chassis showing preamp

V A C U U M T U B E V A L L E Y IS S U E 9

13 T H E A M P E G S V T

1977 Ampeg SVT 1980 Ampeg SVT (Japanese versiohi times until 1967, when a group known as tical to a B-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 from a stock. By 1968 UNI Music had acquired minor embellishments. The B-15 and record cutting amp that Bill built prior to sole ownership of Ampeg. Fender and SVT (as well as many other Ampegs) used the SVT's development.) It was decided Gibson were dominating the marketplace the 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- growing 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 1 can be 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-rodded) B-15 preamp. The Ultra proven their ruggedness in taxicab two- as an industry leader by producing a truly Low circuit is further embellished to pro- way radio service. 'What environment earth-shaking product—the biggest, 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 follower (the "12AU7" portion of City taxi? the 12D W7/7247 which is a dissimilar The Ampeg SVT dual triode tube equivalent to 1/2 of a Bill Hughes would accompany Ampeg's 12AU7 and 1/2 of a 12AX7). The most newest endorsers—The Rolling Stones— In the late '60s the Acoustic 360 had on their 1969 "Gimme Shelter" tour. established itself as the bass amp of choice unique feature of Channel 1 is its midrange control—it uses a tapped Crude, loud, and vulgar, The Stones epit- for the discriminating player seeking the omized everything Everett Hull hated ultimate bass tone (and volume). It toroidal to select the midrange center frequency. The choices are 220Hz, about rock music; his teeth are probably became an obvious target for the Ampeg still grinding! The band torture-tested design team. Their mission was clear— 800Hz, and 3,000Hz. It also uses two additional "12AX7" stages and one more the new obscenely heavy, 82 pound, 300+ beat the 360 in every way possible. The watt SVT (and its alias the V-9). Keith 360 sounded dry and one-dimensional "12AU7" stage derived from 12D W7s. The two channels sum into a 6C4 (simi- Richards and Mick Taylor plugged them due to its all- design, and its into 4x12 guitar cabs, while Bill Wyman folded-horn speaker cabinet design lar to 1/2 of a 12AU7) used as a cathode follower. It's obvious Bill was fond of the used the new 8x10 bass cabs. Their live sounded good in a big room, but sounded album "Get Yet Ya-Ya's Out!" was record- less than impressive up-close. low impedance drive characteristics of a 12AU7 (or equivalent) used as a cathode ed during this tour on November 27th & Ampeg's Chief Engineer Bill Hughes follower! 28th at Madison Square Garden in New was responsible for the design of the SVT York City. Their rather clean guitar and circuitry. The SVT's preamp was derived The prototype SVT (short for "Super bass tones were obtained at what were from the B-15. Channel 2 is nearly iden- Valve Technology") used four 81IA thori- most assuredly excruciatingly loud volume

V AC U U M T UBE V ALLE Y ISSU E 9

14 T H E A M P E G S V T

1969-70 SVT with 6146s

levels. While the 6146B/8298As held up thunderous! OK, so the cymbals were contras primitive integrated circuit. to the mechanically 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 electronics were assembled tolerant of the abuse provided by the shadowed, but from a bass player's point- 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 clipping 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 1". trical differences are in the foreign looking continuously. The SVT would soon be Ahmad's playing displays masterful transformers. They also reduced the B+ 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 ounce of his powerfully dynamic amps, they're still capable of producing a Roger Cox designed the 150 pound performance. The piano sounded as big as sweet and pleasant tone, favored by some 8x10 speaker cabinet. It was intended that a house! Don't get me wrong, I'm not for that reason. The reduced voltages also each SVT head drive two cabinets for a advocating SVTs as hi-fi amps; they really increase reliability slightly. In 1986 total of 16 speakers! In contrast to the don't have anywhere near the kind of clar- Ampeg was purchased by St. Louis Music. Acoustic 360's long-distance focusing ity, resolution, detail, or extended fre- They revived the SVT's waning prestige folded horn, the SVT cab was designed to 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, but if SVTs using the same parts vendors as the It was designed to blow away the Acoustic you're a hard-core bass fiend, it's a sound Magnavox-made Ampegs. Due to limited 360 where it mattered most—the music you'll never forget. availability of 12D W7s and 12BH7s, the store! It used eight 32 ohm speakers wired current SVTs have been redesigned to use in parallel for a total load of 4 ohms per Estimating Year Of Manufacture the more readily available 12AX7s and cabinet. Each horizontal pair of speakers The 6146B/8298A version would last 12AU7s. The preamp has been signifi- resided in its own sealed enclosure. until late 1970, when the output tubes cantly simplified, but the power amp is Essentially, four 2x1Os were stacked on very similar to the original. The output top of each other. A totally revolutionary would be replaced by 6550s. The earliest amps can be easily identified by their transformers are still manufactured by and unprecedented approach to bass short black plastic toggle switches and ETC of Paramus, New Jersey. The power speaker design! In head-to-head shootouts blue lettering on the front-panel. The transformers are provided by an off-shore the SVT would annihilate the Acoustic back panel reads: The Ampeg Co. Inc. source. 360. Bill Hughes and Roger Cox had Linden, N.J.. Rock bassists who prefer to accomplished their mission—to 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 attack. Fender and apparently he knows that the SVT As A Hi-Fi Amp? In 1971 Ampeg was sold to Magnavox SVT power amp is a classic that can't be and the manufacturing was moved to the topped. Just for kicks I set-up a pair of SVTs in Magnavox factory in Greenville, my hi-fi room and accessed the power Tennessee. The early Magnavox amps can Care And Feeding Of An SVT amp sections through their line-in jacks. be easily identified by their metal toggle It became quickly apparent that the gigan- switches and the lettering "Division Of Most SVTs were shipped with Mullard tic-ness of the SVT's sound comes from, The Magnavox Company" on the back made 12D W7s. These were extremely at least in part, the 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 identified by the plastic rocker power you find an SVT with the original 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 Magnavox era amps are generally favored hours of service-life left. They have a provides an incredible dynamic range. for their huge and deep bulldozing bot- strong, muscular sounding midrange drive 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 meanest bass amp. A Telefunken like he was thumpin' away right in front plished by observing the date codes on 12D W7 in the first stage of channel 1 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

V A C U U M T U B E V A L L E Y IS S U E 9

15 T H E A M P E G S V T

V , VS V4 Vs I2DW7 12DW7 1 20W ? 6C4

4 0047 - 1 F-- E 310 02 IATRA'ir .2e .4 cDS 4'7 * 220K 470 1. eon. J, UYTT- T.V VY-* Orr C. CF-1 CHANNEL BASS CLIFT c -. 1 6.466 StLECT _ _ r- ITI • - - no I. - ,-!-- I

l 170V I "33 C4 05 L .26 t 3.34 20 60' .43 §Zele 4 4 l 0?. 00v 04

134. 6 à I .0047 I .0

6. pot 1 (6.TooDa j 9 c o I 10 B V. .6. 1 2AX 7 .6. ' MOT LION 12 7 .. ISID-RAND4 -- 11 1_ -,i VI44 .4 LIN. 154 520 100K V5 V• V3 V2 VI C BRIGHT J, [ IDOIC r/C1 " CHANNEL Td e X 6.3KA.C. 0 .00047 1 10 - - o ICI 101401.L R -Ce2 SpIs IN 1.06. F.PD-P ANGE n_ .4 BA I 011 120 ERED. EELECT ,, F P 23 0 -ULTRA I 20« 2 K I. 0 0 . 4 NO.

E.444 t5. MODEL NOTES -DLL REEIS TOPS 114 0111AS br Ht. UNtESE OTNE11141. SPECI+1.. SVT PR EAMP -., CADACIADIS IN In0 l 400v • -DC VOLTAGE REAM. DAN NO SIGNAL APPLIED USING A U.S. PATENT PEMANG ut,ceon put too vountut. -. MRS IN moons. 52122 TO 40E4 DART 40. ;aI enipe g DAN. 57 CATE NO .AT CR C.C. 669 06604 4(.0204 A

...... THE BIAS CAN BE ADJUSTED BY ____:‘,. .H. (b. 61458/229BA REMOVING THE READ CABINET ' 2 ,--- -, 1 1 V. I BAFFLE. USE A LONG ROD MID TAP i '''. I I t213147 ...... ---- 1 THE BAFFLE FREE FROM THE HEAD- St .., ; LOCK RETAINERS. GAIN ACCESS 2 i>,. • I,.., 1 f'''' ; _LC, •S •73 OP THE CABINET BY J -- 7ç---e) J. ".. .31 ..f ?ROM THE REAR -. 0 '7, fo ....le, 7.211 1 7' T ,....1.- .., USING THE SPACE AVAILABLE 1 5 “Ii..1. 1,” ' Yee «.- THROUGH THE COOLING FAN BLADES. " ', 111se ' % I I -- .es .3. ..., I 5 11 3. AK 474 47K

• - . - -. I 1 ' - • IA - - IA. OA SP. 3717731 0 I aka MIES ito I» i P73 • f - - - -I MA G 00 j0 •. oak 4 22. LtA 4 _ 2 I.t A .7 roe. WA. SEE 3.4. 1, 4 4D44. C.44004 .. WE • A 8 C ..• C.O. Es. 6. tug. ....e6.".1 (*moon ...• CALIBRATION PROCECURE 1E a n. MR .24 .3? 0-42 . e, ,- + - C.«. A • DN. WAD 0.41. 10 MS F4 4 DM OM-

ei r-le r c t - OANT EV. WI CAM. ..60..111101, .. .6 .. roc ee IL •- AULD, 4.0., FDA .4 An MT, D.C. KT.. 4, NM MOM. 1. .167 SU 6-3.11.44 VII •04 1104 ±.. «Alf Kt«. xt me r.. . ID , . 11 4 .4 t , m.. 1 - 4.44 nn.172 ZALAOL .07024. ADMAN., e 5 WS" 514 ID. 1 n 4-7141.1. W .I. el. UM W 7, D.( MIL». IV 3.01.14 4.41.3. C. 47 40 RI Ii. «MCI 01.01.1.0 WY TO IA» .4.7011, 311.141 DIV, NM SOV 1 Mr. NETC.+04 f - il-VOLT WA* .7.0 : ....151 .7.7 IA ID SAP 3-4 NO 4 , - CONNECT D.C. OW .517 MI.. A.. MAT 44 4 fo , ADA41 •I44 AA 304 tAt 4.1. 4,. 22 _ - . V .iI& Vs VS V, A no WAD .. .I 4.40 44 441.1 70 emosm. T. ME N. ,.....' N.01 CD 7. Atatiri., 04 3E0 wen V. 6146B/8298A D 'coca. NM noe4 14 128117 MA. 114S4% e g •Et tA c4E . M ai -NI 14144.4 ¡V. a. emus me.. mom, GEM. -ND CAI... IN EDO. • 4004 41.4.4 A.M. MO M. .14420.11 -D.C. 404.7.. REA.. DAD . SODA ADINAD,D41. A 4.6 20,003O PU V0.7 KA.. OM 44 AA 44 t o• -1. -le. 4, COMAE« A .....c.»,..... At POINT EI, EEL .• DILL lust 10 m et.. 1 .4 1 -NDAKEE ID mg.... nu. 10 metes nut to...... _ .4. MODEL : CIRCUIT OF CHASSIS MAY VARY SLIGHTLY FROM THAT SHOWN j S VT I a POWER AMPUFIER Ia. Z ' HERE DUE TO NORMAL PRCOUGTION CHANCES. IUD • i ampeg 0...lean ..... = 1.e.L . 11: Va lt. W vc v. IA V9 4.30011) - ...... = S.C. 1770 05700 -- 17

V AC U U M T UBE V ALLE Y ISSUE 9

16 T H E A M P E G S V T that's what you're seeking. I've tried the Speaking of bias, the originally specified should be cleaned regularly as well. Early well-known 12AX7 conversion and found idle current of 24 ma per tube could be SVTs had the speaker cable permanently it changes the sound; I prefer the sound of considered a bit conservative. If you attached to the amplifier; this cable has 12D W7s. 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 fattest drive for tubes (Chinese 6550s need not apply), replaced with a speaker jack, since an the output stage. Try to find a matched you might be tempted to try a bit hotter intermittent load on an SVT can be quite pair—triode 1 should match triode 1 of bias. My richest, best balanced, and most spectacular! It's best to think of an SVT as the other tube in transconductance and refined sounding SVT has six Genelex a high performance = high maintenance cathode current. Triode 2s should also KT88s idling at about 33 ma each. Some machine, akin to the muscle cars spawned match. SVTs were shipped with Tung Sol in the same era. 6550s—these have an incredibly detailed You should try to match everything in midrange and lacy top better suited for True tube amp connoisseurs will have the push/pull output stage: control 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 SVT: 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 these the GE 6550s. The sweet and clean multi-dimensional air and space, the pow- resistors and the tone of the amp. I've seen sounding Svetlaria 6550C compliments erful sense of breadth and depth, and the 10 ohm plate resistors that measured over the sound of the Japanese built MTI amps taut transient wallop 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 excessively hard—watch for hot-spots. I've Ampeg SVT. the output transformer taps were incor- found the Teslovak KT88's bias to be rectly wired to the switch on the extension prone to instability and the tubes can arc speaker jack. When the extension jack is unexpectedly. The GE 6146B/8298A Terry Buddingh is a performing bassist and not in use the normal output jack should (with the flat 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 I contributor and guitar amp reviewer for code on the schematic. The truly obsessive wouldn't stray too far from the recom- Guitar Player Magazine and related publi- will probably want to replace the 15K bias mended 24 ma per tube idle current. cations. and drive balance pots with 10 turn Heli- Then again, sometimes biasing is a test of pots for less sensitive and more 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 Tube Lore A REFERENCE FOR USERS AND COLLECTORS ELECTRA-PR1NT For serious users, a new look into tubes from 1920 to the present: history of design trends, "where us- AUDIO ed" information, tech data, equivalencies, "user's guide," even auction prices. See review by Eric QUALITY HANDWOUND S.E. OUTPUT TRANSFORMERS Barbour in the Winter 1997 ¡"TV. Contains 186 pag- • Primaries from 1.8K to 10K es, 8-/12 " x 11" softbound. Orderable from: • Exclusive wideband design Antique Electronic Supply, (602) 820-5411 • 16, 8, 4, or 2 ohm secondary 6221 S. Maple, Tempe, AZ 85283 • Gold plating Antique Radio Classified, (508) 371-0512 CUSTOM-BUILT POWER TRANSFORMERS/CHOKES PO Box 2, Carlisle, MA 01741 • Wound to your requirements Museum of Radio ez Technology Bookstore • Heavy-duty design for Class A use 4204 Thorn Apple Ln., Charleston, WV 25313 • DC filament supply windings • W7FG Vintage Manuals, (800) 807-6146 • HV chokes to 15H, 300ma 3300 Wayside Dr., Bartlesville, OK 74006 • Low voltage, high current filament chokes Or order directly from the author: Component pricing and specifications catalog available Ludwell Sibley 44-V E. Main St. ELECTRA-PRINT AUDIO Flemington, NJ 08822 4117 Roxanne Drive Las Vegas, NV 89108 Price if ordered direct, postpaid: $19.95 in US or Canada, 702-396-4909 FAX 702-396-4910 $24.95 ppd. elsewhere. Discounts available to groups on orders on quantity purchases.

V AC U U M T UBE V ALLE Y ISSUE 9

17 T H E F IR S T P E R S O N A L C O M P U T E R S

around 1954, had similar problems.

Computing With Tubes: The first programmable computers to use were experimental units, hybrid in construction: RAND The Savage Art Corporation's JOHNNIAC in 1954 and Lincoln Labs' TX-0 in 1955. The first all- transistor calculating machine to be 3. The First PCs Were Not Made In 1975 demonstrated, a multiplier built by Bell Labs in 1951, used point-contact devices By Eric Barbour © 1998 All Rights Reserved and was unreliable. Further, the first pro- grammable all-transistor computer, Bell Labs' Leprechaun of 1956, was an experi- The so-called "digital revolution" contin- sounds, the "personal computer" predates mental prototype only and was not manu- ues to steamroller on. Driven by hype and even the use of transistors! For by 1955, factured due to reliability issues. Until the avarice, this movement is facilitated by numerous small computers were in daily supply of junction devices was steady and the public maunderings of a gang of use in scientific and business data process- consistent in quality, they had to be indi- remarkably ignorant journalists and self- ing. All were intended for 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 consistent example was a special section in the San typical office desk. These machines tend- and more reliable. Jose Mercury News of March 2, 1997. In ed to have a typewriter for input-output, this supplement, called "Behind The usually the popular (and slow) Friden So: up to 1958, building a computer Wave," various MERC scribblers were Flexowriter with paper-tape reader/punch. meant using tubes. Luckily, the availabili- given plenty of space to blather about And nothing else. Some of the larger ty of decent germanium diodes 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 requires e-mail and the World or a simple CRT for primitive vector- were done with tubes. Despite misconcep- Wide Web. Overall, it looks like a busi- based graphics. Yet these are all basically tions about tubes constantly "burning ness-friendly puff piece, 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 machines contain no time without failures. Nearly all the the United States and intended to make integrated circuits, they did not even use things we take for granted today in com- local advertisers feel warm and happy transistors! puters were developed with tube technol- inside. Yet this particular item simply ogy. If more proof is required, following regurgitated the long-held homilies about Why? Well, the semiconductor devices are descriptions of the world's first per- the development of computing--many of of the early 1950s were very primitive. So sonal computers. You won't find a single which are distorted, if not outrageously little was known about this technology transistor in any of them. false. that early point-contact devices, commer- cially available Ask any Silicon Valley engineer: what (and expensive Bendix G-15 _ was the first personal computer? Since for many years), there is no hard-and-fast definition of a were in fact bare- (Courtesy of the PC, you will encounter as many answers ly adequate for Computer Mu,(1,,72) as there are engineers in Silicon Valley. If use in pocket the person being asked is knowledgeable, AM radios. The the most likely response will be the MITS Mercury News Altair of 1975. This was the first PC to be people claim that "widely" available to hobbyists, at a "low the invention of cost"--whatever that means. (These folks the transistor in usually fail to mention even earlier 1947 changed machines: IBM 5100, Scelbi 8H, Micral.) computing, yet Yet one could make an excellent 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 circa 1958. made Micral. At first they were point-contact, If we want to define a "personal com- had low gain and puter" as physically small, generalized in very high noise design for a variety of scientific and com- figures, varied mercial uses and intended 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 started to appear Yet as horrible and heretical as this in quantity

V AC U U M T UBE V ALLE Y ISSU E 9

18 T H E F I R S T P E R S O N A L C O M P U T E R S

Burroughs EI01 ment with their massive ugliness. By com- (Courte.y 6ft he Computer Museum) parison, the Librascope computer had loads of STYLE. And it cost a mere $39,600, a pittance at a time when typical mainframes were $200,000 and required a staff of 3 to 10 people to keep them run- ning.

The LGP-30 was remarkably advanced, in spite of the lack of transistors. Its inge- nious design, by Dr. Stanley Frankel of Cal Tech, used a minimum of electronics and was totally serial-synchronous. Operating registers could be displayed on a small CRT. Main memory was 4096 words on a magnetic drum, and given that 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 II. Only 112 tubes and 1500 germanium diodes were enough to do everything required. Sixteen machine instructions, and why have any more? Input and output was by Flexowriter, and Bendix G-15 length encoded each digit. A word was 12 adding peripherals was difficult at best. digits wide plus a sign bit, and 220 words Imagine a big art-deco-like refrigerator Add time was 8.75 milliseconds, very fast were stored on its magnetic drum. Adding from the 1940s, and you'd have the G-15, compared to similar machines like the took 50 milliseconds due to the time-divi- one of the most popular computers of the Burroughs E101. This slick little gadget sion scheme of its logic, and due to the weighed 800 pounds, used 1500 watts 50s. It was simple and small enough to slowness of the drum memory. use in a typical office. Memory was a and required only a small window-type air magnetic drum, as usual for this period, It and the similar E102 had a plug- conditioner in warm weather. holding 2160 words of 29 bits each. board panel, removable to allow exchange. Since the drum held data with the Registers were on a special fast-access part 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 microsec- panel settings. This was thought to make switched back on. And a good thing too, onds—slowed by the need to access the the programs shorter and simpler. The since it had to be re-entered from a drum, typical for all drum-memory keyboard and printer were a Burroughs 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 fairly fast computer. normal business-accounting uses. system had a simple console monitor and Programs were read from a paper tape Unlike the LGP-30 below and some subroutines for computation. Reliability operating at 2 characters per second. The was apparently excellent, with no service others, the G-15 could accept various E101 consumed 3000 peripherals. Magnetic tape drives, paper watts and weighed tape and card punches, and even a plotter Librascope LGP-30 and guest 1800 pounds. It should •-'-sy Lockheed-Martin Libre---'7" were available. A basic G-15 used 400 be easy to see why the tubes, mostly 5967s, and 3000 diodes. E101 was quickly Addition of peripherals required an exter- eclipsed by faster nal interface cabinet. Operating uptime machines with more was reported to be 90-98% for typical memory capacity. users, many of which were defense con- tractors or state highway departments. It Librascope LGP-30 is reported that the Nebraska Highway Department was using a G-15 until 1982. This was unquestion- Considering that more than 200 G-15s ably the coolest, 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 E101 and E102 industrial designers, and wrapped in a slick One of the first desk-sized computers, metal case with a the E101 was wildly popular with defense chrome accent strip. contractors and military agencies, as well Other small computers as banks and other kinds of companies. usually were sold in More than 80 had been sold in the first 4 ugly grey or dark-green years after the 1953 introduction. It used boxes, intended to "pulse-coded decimal," meaning it was impress the manage- not capable of static operation--pulse

V A C U U M T U B E V A L L E Y IS S U E 9

19 T H E F I R S T P E R S O N A L C O M P U T E R S technician being needed on the company be ignored and belittled. So it is with that staff. Tube failures occurred only at inter- Mercury News piece, a litany of self-ser- vals of weeks, comparable to that of many vice filled with corporate propaganda. transistorized mainframe systems of the One cannot take seriously a piece of 1960s. journalism" which claims that the only important thing to happen in computing The LGP-30 sold until more powerful between 1947 and 1957 was the birth of small computers, such as the IBM 1620 Bill Gates; which does not mention any (which was apparently introduced specifi- of the important pre-ENIAC machines or cally to compete with the Librascope), any software developments of the 1950s, appeared in 1959-1960. A few LGP-30s, Their Readix machine was aimed at such as the first operating systems and donated by the engineering firms that defense customers for engineering work, FORTRAN; and which fails to cover originally bought them, were being used though it was also claimed to be suitable milestone systems of the 1960s such as 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. Readix was Precision marketing firm, who then stuck expandable, with optional point plotter, One final note: some VTV readers may their own logos on it for sale. So, the magnetic tape drive, and an interim regis- have heard that early microcomputers like LGP-30 was apparently the first "generic" ter for attaching IBM punch-card units. the Scelbi are so rare that they sell for PC. Royal ran ads for the LGP-30 in a A word was 10 BCD digits, add time was $8000 and up--yet the Scelbi is relatively variety of magazines. 17 milliseconds including drum access, common, compared even to popular tube and the drum held 4000 words. A feature computers like the LGP-30 or the G-15. The LGP-30 even got its own high- 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 these machines yet. called ACT-1. Unfortunately its transis- of the era, was an oscilloscope for trou- And this article does not even cover very torized replacement, the RPC-4000, was bleshooting. Free, at no extra charge. specialized machines, like the Litton announced at about the same time. This, 20/40 differential analyzer or the Baird the 1620, and other frantically intro- Underwood Elecom 50 Atomic 580 autocorrelator. duced transistor computers of the period sent the LGP-30 into the dustbin of his- All the business-machine manufacturers Hopefully, this information about the tory by 1960. Librascope later became a tried to jump into the computer world earliest "personal computers" will help to builder of computer systems for defense during the 1950s. Underwood, a venera- dissipate the historic information void in work, and is currently a division of ble typewriter manufacturer, was no which American computing currently Lockheed Martin. exception. Their Elecom 50 was first wallows. And it should correct some false delivered in 1955, and it followed their verities, repeated ad nauseaum by people Monrobot III successful Elecom 100 of 1952. Elecom who should know better and are paid to 50 roughly corresponded to the know better. Monroe, a reputable maker of mechani- Librascope machine, with 160 tubes and cal calculators, entered the electronics 2000 diodes. Words were 10 decimal dig- Bibliography business with the Monrobot series. The its, and the drum memory held 100 loca- smallest was the III, yet another desk full 1. Logical Design of a Simple General- tions plus the 3 working registers. of tubes with a Flexowriter on top. The Purpose Computer, IRE Transactions on Apparently the I/O console was numeric first sample was sold to the US Air Force Electronic Computers, Stanley Frankel, only, while an alphanumeric printer was Cambridge Computing Center in 1955. volume EC-6, number 1, March 1957. an extra option. With 800 tubes crammed inside, it had a 2. A Second Survey of Domestic not-so-good uptime record of 80%, and The Elecom 50 used 2000 watts, Electronic Digital Computing Systems, outside of hard failures, Monroe required weighed 750 pounds, and cost a mere one hour of regular maintenance every Martin H. Weik, Department of the $22,500--a real bargain. More than 50 Army Ballistic Research Laboratories, day. Its drum held 100 numbers and 100 had been sold by 1957, and the delivery Aberdeen Proving Ground, Maryland, program instructions, in separate areas. time was 12 months. In spite of its tiny Report 1010, June 1957. Addition of two 20-digit decimal num- memory and limited console, the low bers required 0.12 seconds, including price found it many applications. One 3. IBM'S Early Computers, Charles J. drum access. Just reading a location took ominous note: average running time Bashe, Lyle R. Johnson, John H. Palmer, 15 milliseconds, and the system ran on a between calculation errors was quoted at Emerson W Pugh; The MIT Press, 10-kHz clock. And it used 2500 watts 6 hours. Like all these machines, the Cambridge, Massachusetts, 1986. and weighed 1000 pounds. Even the larg- Elecom 50 had no error-checking sys- er Monrobot V was just as slow and tems. Calculations had to be re-run or 4. Military Systems Design magazine, primitive. Interesting, that early comput- checked by other means to ensure correct November-December 1959, p. 311 and ers made in-house by big business- results, primarily due to bits being read 318. machine companies tended to be poorly incorrectly from the drum occasionally. designed. Many thanks to Richard Kennerknecht of Exit Lockheed Martin Librascope and Dr. Readix So long as instant experts continue to Leonard Shustek of The Computer Museum J. B. Rea Company was a "start-up" spread misinformation unchecked, the for their invaluable assistance in research- firm that did not survive the early days. true nature and origin of computing will ing the facts in this article.

V A C U U M T U B E V A L L E Y IS S U E 9

20 W IN T E R 1 9 9 8 C E S R E P O R T

audiophile "screechies", while still deliver- Winter 1998 ing a credible 3-D image. Great for hours SOU N D of casual listening. Very close second was CES Report the Thor Audio system, with tweaks cour- PRACTICES tesy of Mike Vans Evers. By Eric Barbour e 1998 M AG AZINE Now for the part you're all waiting for, It seems to get bigger each year. And the WEIRDNESS: every year, there are more and more vacu- a) Ralph Karsten of Atma-Sphere was um-tube products. Not only was the I DIY Projects ° showing off his newest invention: a 300B Winter CES high-end exhibit at the OTL amp. That's what I said, a 300B istory and Classics Alexis Park Hotel in Las Vegas the biggest OTL. Only four 300Bs are suitable to yet, the "alternative" International High- drive a 16-ohm load to 20 watts. I heard uture Perspectives End Show was expanded to two hotels-- it and can attest to its excellence. the Debbie Reynolds and the Howard Johnson on Tropicana. And even though b) Unfortunately, Moth Audio's huge nternational News many listed exhibitors didn't make it, 304TL SE amps weren't ready yet, and tot - - there were easily 60+ companies showing WAVAC Audio Labs did not have an Wild Entertaininent tube electronics, almost a 2-to-1 ratio exhibit of their giant 833A amps. Even so, over solid-state manufacturers. there were plenty of companies that were Refuge for Audio totally unfamiliar to us. Audiomat, and much more!! It would be impossible to choose best Musica Nova, Wyetech, plus the firm in sound, as there were so many excellent the next item. systems (and a few bad ones). And I did- SUBSCRIPTION RATES n't have time to hear even half of the c) Lars-X Audio of Singapore showed I year (4 issues) '20 US,s24 Canada, demonstrations. their speaker system--a heavily modified 90 Europe, 95 elsewhere. Lowther driver in a transmission-line cab- Sample '5. MC/Visa accepted. Best bass: No question, Dr. Bruce inet. Vastly better sound than ordinary Money back if not delighted. Edgar's new 35 Hz folded-horn subwoofer Lowther setups. Driven by their prototype is one of the world's most efficient cinder- PSE 6AS7 amps. Great imaging, and PO Box 180562 Austin TX 78718 block pulverizers. And of course, his some bass too. 512-339-6229 voice/fax matching Series 80 horns are one of the best horn speakers available in the world w ww.soundpractices.co m today. End of discussion, and forget those old Altec or WE theater horns. G) one electron 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 High Quality for a Reasonable Price new Hovland EL34 amp and matching tube preamp. Although it was heavily tilt- Designed and Built in the USA ed in the treble direction, the stereo image seemed 100 feet wide and showed MAJOR front-back solidity plus height. Note to Mike Kerster: don't change any- thing! The SF amps imaged excellently and were more tonally accurate than the Hovland.

Best rock system: Demeter's 6550C d) Tim de Paravidni outdid even him- self by showing an amp that uses twenty amps, paired with Aerial Acoustics speak- 12AX7s as output tubes. Don't laugh, it ers, gave a powerful show without any glare or unnatural treble overtones. Not sounded excellent. Ask our own John Atwood about this—he's been experiment- UBT-1 Designed for parallel operation of: to forget Atma-Sphere's system, or Moth ing with 12AX7s as Class A2 power tri- 1.6k prima-y 2A3s, EL34s, 300Bs 6AS7s, Audio's SV572 amp slamming into Von 15 watts $90.25 etc. or Sweep-tube in Schweikert speakers. odes recently, and reports great results. 160 mA 'enhanced triode' mode One watt output per tube.... UBT-2 Best secret design: David Berning's new e) A brief visit to the Sands Convention 4.8k primary Can be used with: 5811 amp, using obscure RF switching 15 watts $ 112. 10 30013 50, SV811-3, etc. power techniques to get 35 watts from Center uncovered three car-amp manufac- 110mA _ one tube. Sounded great, also deserves to turers using tubes. Planet Audio, UBT-3 Poweramper, and Phaze Audio all used be in the Most Tonally Accurate category 3k primary -- tubes as gain stages with conventional Good for single ended along with Sonic Frontiers. 15 watts 21.60 transistor outputs. :110mA 2A3 or 3008 Pleasant musicality: Mesa's new Tigris Quantity discounts available integrated amp, paired with the Samadhi ANTIQUE ELECTRONIC SUPPLY Acoustics cube speaker. Not accurate, but damn nice to listen to and free of the 6221 S. Maple Ave. • Tempe, AZ • 85283 Phone 16021 820.5411 • FAX (602) 820-4643 or 800 706-6789

V AC U U M T UBE V ALLE Y ISSUE 9

2 1 V IN T A G E A U D I O I N J A P A N

in order to build up trust. The Internet will certainly 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 cater to Japan collectors and tube enthusiasts. This article and others that follow will review classic equipment and related com- 1. Amplifiers and ponents that are in demand in Japan and other places. What most people would By Charles Kittleson © 1998 All Rights Reserved throw out as junk could be worth the price of a new car and more. The prices listed 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 the masses, were quietly rebuild vintage tube equipment that will Technology. Prices are quoted in Yen and buying up classic tube audio equipment be sold to collectors, as this can reduce you must convert to US dollars. 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 to this condition 130 Yen per US dollar. The wide varia- getting misled into believing that Pioneer, due to past experiences of friends who tion in prices is due to equipment condi- Sansui and Sony audio gear with all the purchased WE gear through the mail that tion and to individual shops that price fancy features and switches was better turned out to be junk. Speakers must items more expensively. In the high- than the old stuff. Sometimes I think have the original cones, and vacuum tubes priced shops, buyers in Japan can negoti- most people were so out of it back then should be new in their original boxes, for ate 10 to 30% off asking prices. that they didn't realize solid state gear best prices. Remember that you will not be able to really sounded like crap. Even though I fetch these prices in the US. What you am writing this article now, it should have The vintage audio market in places such can expect is anywhere from 25 to 40% been published 20 years ago. as Hong Kong, Taiwan, Korea, Singapore, etc. has recently been strong as well. of the prices quoted here when dealing Back in the 1970s, dealer/exporters However, these Asian buyers are often less with reputable dealers. Also remember were running want ads that would offer particular about condition and also more that demand and prices for any of this to buy your old McIntosh or Marantz open to other brands such as Fisher, equipment are extremely unstable and tube gear for $100 or less so you would Scott, Dynaco, EICO, Acrosound, etc. subject to 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 "dealer/exporters" 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 type may have to settle for what is offered if salers and exporters or directly to retail of tube audio gear and tend to work on you are in a hurry to unload the gear. shops in Akihabara, the electronics dis- much lower mark ups. The Asian economy is in turmoil right trict of Tokyo. By the time gear was now, due to the economic bubble which placed on the retail shelf, the price went Today, there are dozens of would-be burst a few months ago, so demand on up between five and ten times the original dealer/exporters advertising in the back of many items may be soft. In addition, price. Many of these dealers unobtrusive- audio publications with a typical ad read- younger engineering-oriented Japanese ly made high six figure incomes by ing: "Wanted: Marantz, McIntosh, audiophiles are not as eager to collect WE exporting our old audio "junk." Western Electric, Tannoy Cash Paid." Many of these fellows are purchasing the and other vintage gear as the older 45 + Japanese audiophiles were and are very good stuff from junk collectors, garage year old crowd. However, well-to-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 clue as to the value of more active in collecting vintage audio tubes, amps and speakers, McIntosh tube this equipment. Unfortunately, most of now so the demand is still there. the classic audio gear has already been audio, Marantz tube audio, Tannoy loud- NOTE: Only selected vintage gear is list- exported. speakers, Altec Lansing tube equipment ed on pp. 23-24 due to time and space and speakers, JBL loudspeakers and RCA considerations. A more detailed Vintage vacuum tubes. The Japanese are particu- If you have any of this gear and are Hi Fi Price Guide ($30) is available from larly obsessed with Western Electric. thinking of selling it, shop around to get VTV, and is advertised elsewhere in this Capacitors, wire, resistors or anything your best price. Some dealer/exporters publication. marked WE demands premium prices. have a direct connection to either a shop or distributor in Hong Kong or Tokyo This is due, in some part, to reviewers in This article is Part I of a three-part series and may be able to pay more. Other Japanese audio magazines writing exagger- related to collecting and pricing vintage ated words of praise about the virtues of dealers may have to go through two to audio equipment and related accessories. WE equipment. On the other hand, there three "middlemen" or wholesalers. Of is little or no demand for many other vin- course, each middleman has to take his A special thanks to Hisashi Ohtsuka, Senior tage audio brands, such as Scott or Fisher. "cut." Some individual sellers have been successful dealing directly with buyers Editor, MJ Magazine, for his assistance Condition is everything to Japanese from retail stores, but this can take time with this article.

V AC U U M T UBE V ALLE Y ISSUE 9

22 V I N T A G E A U D I O I N J A P A N

Amplifiers and Preamplifiers Low Value High Value

Altec

126A (push-pull 6L6 amp) Y250,000 Y350,000 pair 128B (push-pull EL34 amp) Y200,000 Y250,000 pair 256C (push-pull 807 amp) Y250,000 Y350,000 pair 1520A (push-pull 6L6 amp) Y250,000 4300,000 pair 1530A (push-pull 6146B amp) Y275,000 Y350,000 pair 1567 (tube preamp) Y250,000 Y350,000 pair 1568A (push-pull 6CA7 amp) Y140,000 Y190,000 pair 1569A (PPP 6CA7 amp) Y160,000 Y225,000 pair 1570B (push-pull 811A amp) Y280,000 Y350,000 pair 287 (push-pull 845 amp) Y440,000 Y1,000,000 pair 287W (push-pull 805 amp) Y450,000 Y1,500,000 pair Ampex

807 push-pull theater amp Y150,000 Y200,000 pair 6550 push-pull theater amp Y200,000 1250,000 pair Altec 256C Amplifier Altec 1570B Audio Research

SP-3 (tube ) Y150,000 Y200,000 Brook

12M (push-pull 2M amp) Y250,000 Y400,000 pair Model 10 series (PP 2A3 amp) Y300,000 Y600,000 pair DYNACO

MK III (push-pull KT88 amp) Y90,000 Y130,000 pair MKIV (push-pull EL34 amp) Y100,000 Y140,000 pair HK Citation II Amp Dynaco Mark III PAS-3 (tube preamplifier) Y50,000 75,000 SCA35 (EL84 integrated amp) Y50,000 Y110,000 ST70 (tube stereo amp) Y75,000 Y130,000 Fisher

SA300 (stereo EL34 amp) Y80,000 Y100,000 400CX (tube stereo preamp) Y120,000 Y150,000 80C (mono tube preamp) Y100,000 Y120,000 Harman-Kardon

Citation I (tube stereo preamp) Y135,000 Y160,000 Citation II (6550 push-pull amp) Y160,000 Y250,000 International Projector Corporation (IPC)

1001 (push-pull 6L6 amp) Y175,000 Y350,000 pair 1011 (push-pull 6L6 amp) Y200,000 Y250,000 pair 1026 (push-pull 807 amp) Y225,000 Y300,000 pair 1027 (push-pull 6L6 amp) Y250,000 Y300,000 pair 1029 (SE 6L6 amp) Y150,000 Y235,000 pair Langevin

101D (6L6 push-pull amp) Y250,000 Y380,000 pair 138 (6V6 push-pull amp) Y140,000 Y200,000 pair Maranta J 'M Tuner Marantz

Model 1 Consolette (mono preamplifier) Y300,000 Y500,000 pair Model 2 (push-pull EL34 amp) Y440,000 Y750,000 pair Model 3 (crossover) Y300,000 Y350,000 pair Model 5 (push-pull EL34 amp) Y380,000 Y600,000 pair Model 6 (stereo adapter) Y150,000 Y180,000 Model 7C (stereo preamplifier) Y350,000 Y600,000 Model 8B (stereo push-pull 6CA7 amp) Y280,000 Y400,000 Model 9 (PPP EL34 amp) Y1,200,000 Y1,800,000 pair Model 10B (FM tuner) Y280,000 Y650,000

V A C U U M T U B E V A L L E Y ISS U E 9

23 V I N T A G E A U D I O I N J A P A N

Amplifiers and Preamplifiers Low Value High Value

McIntosh

A116 (push-pull 6BG6 amp) Y190,000 Y250,000 pair C11 (tube preamp) Y150,000 Y300,000 C20 (tube preamp) Y150,000 Y325,000 C22 (tube preamp) Y250,000 Y560,000 MA230 (tube integrated amp) Y150,000 Y180,000 MC30 (push-pull 6L6 amp) Y180,000 Y275,000 pair MC40 (push-pull 6L6 amp) Y250,000 Y280,000 pair MC60 (push-pull 6550 amp) Y250,000 Y350,000 pair MC75 (push-pull KT88 amp) Y255,000 Y410,000 pair WE Type 124 Amplifier MC225 (stereo push-pull 7591A amp) Y180,000 Y250,000 MC240 (stereo push-pull 6L6 amp) Y225,000 Y375,000 MC275 (stereo push-pull KT88 amp) Y400,000 Y800,000 M1200 (push-pull 8005) Y1,200,000 Y2,500,000 pair MI350 (350 watt sweep tube amp) Y1,500,000 and up per pair MR65B (FM tuner) Y80,000 Y135,000 MR66 (AM/FM tuner) Y140,000 Y180,000 MR67 (FM MPX tuner) Y130,000 Y175,000 MR71 (FM tuner) Y150,000 Y200,000 MX110 (tuner-preamp) Y180,000 Y275,000

QUAD

22 preamp, II power amp Y300,000 Y400,000 pair WE Type 57A Amplifier WE Type 87B Amplifier

H H Scott

250 (push-pull EL34 amp) Y110,000 Y130,000 pair 130 (tube preamp) Y110,000 Y120,000

Western Electric Amplifiers

41 and 42 (rack mounted amp) Y2,000,000 Y3,000,000 pair 43A (push-pull 211 amp) Y700,000 Y1,500,000 pair 46 (push-pull 205D amp) Y800,000 Y1,800,000 pair 57-A (push-pull 252A amp) Y900,000 Y1,500,000 pair 86, 86-A (push-pull 300B amp) Y1,500,000 Y2,500,000 pair 86B (push-pull 300B amp) ¥2,000,000 Y3,000,000 pair 87B (push-pull 845 or 284-C amp) Y1,500,000 Y2,500,000 pair TA 1086 (push-pull 300B) Y1,500,000 Y2,500,000 pair 91A (single-ended 300B) Y1,600,000 Y2,000,000 pair 500A (91, power supply and speaker) Y2,000,000 Y2,500,000 pair 92A, B (push-pull 300B) Y1,500,000 Y2,000,000 pair 94A (push-pull 6V6/WE349 amp) Y750,000 Y900,000 pair 109B (push-pull 6L6 amp) Y800,000 Y900,000 pair WE Type 86B Amplifier 118A (PPP 6L6 amp) Y500,000 Y750,000 pair 124A-D (push-pull 350B amp) Y1,000,000 Y1,450,000 pair 142A (PP 350B amp) Y700,000 Y1,000,000 pair 143A (PPP 6L6 amp) Y550,000 Y680,000 pair

Western Electric Preamplifiers

105A (high-gain program amplifier) Y1,300,000 Y1,700,000 pair 106A (line amplifier) Y1,200,000 Y1,500,000 pair 120B (low-level pre-mixing amplifier) Y900,000 Y1,250,000 pair 121A (fixed-gain amplifier) Y1,000,000 Y1,650,000 pair WE Type 91A Amplifier WE Type 143 Amplifier 129B (mic preamp) Y1,000,000 Y2,000,000 pair

V A C U U M T U B E V A L L E Y IS S U E 9

24 DIS T O RTI O N A N A L Y Z E R S P A R T 2

meter reading in the top 2/3rds of the meter scale. This number, multiplied by The Audio Test Bench: the level switch setting, is the IM distor- tion. Distortion Analyzers A very helpful modification to the Heathkit IM analyzers is to add an output jack after the demodulator stage, before The Audio Test Bench Part 2 the amplitude detector. Connecting this 00 0 signal to an oscilloscope shows the distor-

nrina I ° tion waveform. This is not the same as ©1998 All Rights Reserved 0 0 I ° by 0 0 0 0 0 r; the residual distortion waveform from a 0 0 O O John Atwood harmonic distortion analyzer, but is very handy in seeing what part of the 60Hz waveform is distorting, catching overloads and clipping, and in seeing high frequen- In part one of this series (VTV #8, page this generally worked well in showing cy parasitic oscillations. 30) the general concept of distortion tube power amplifier . analysis was presented, 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, distortion analysis was discussed. In this though. The fact that the analyzer was Most published distortion measure- ments are for THD (Total Harmonic article several actual distortion analyzers completely self-contained was convenient. will be discussed in detail. In the next and Distortion). Having only an IM analyzer last article the interpretation of the mea- On graduating, moving to California, kept me from comparing my measure- sured results will be covered. and making good money as an engineer, I ments to the rest of the world. At a ham could finally buy a distortion analyzer of radio swap meet, I picked up a Hewlett- To give a good idea of the methods of my own — this time the newer Heathkit Packard 330B harmonic distortion analyz- use and capabilities of distortion analyz- IM-5248 intermodulation analyzer. This er. After getting a copy of the manual, I ers, a detailed description of several dis- was solid-state, and had lower residual discovered I had only half an analyzer - it tortion analyzers that I have had experi- distortion — but was the same concept as needed an external low-distortion sine- ence with will be given. This will be 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 to put tube amp experiments, and is still on the good specs. The lowest distortion reading the use of these analyzers in perspective, shelf as a back-up analyzer. Fig. 1 shows on the 330B was 1% full-scale, but the and shows the growth in sophistication of the signal flow in the Heathkit IM analyz- residual distortion 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 the analyzer in testing a power adjusting pentode screen voltages, etc.) I The Heathkit Years amplifier, the two-tone output is connect- could only get the residual distortion ed to the amp input, a suitable dummy down to about 0.15% — not 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 Columbia-Princeton connected to the amp, and the analyzer annoyance was an odd band of distortion Electronic Music Center in New York. input is connected across the dummy at low levels — almost the opposite of The first audio analyzer I was exposed to load. After making sure that the low fre- cross-over distortion — in the distortion was an old Heathkit IM-48 intermodula- quency signal (60Hz) is exactly four times output waveform. This is caused by H-P's tion distortion analyzer. Many amplifiers, the amplitude of the high frequency sig- use of an AC meter circuit that places the line amps, and tape recorders were tested nal (7KHz), the two-tone output is meter rectifiers inside the overall feedback on this 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 the 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 input level of the analyzer is adjusted for readings on our own equipment. This a full-scale reading on the meter. The ana- To use this type of THD analyzer, the type of analyzer was limited to the lyzer is then switched to the "IM" mode, sine-wave oscillator is connected to the 60Hz/7KHz SMPTE test, which primari- and the input level switch is set to give a amp input, and the analyzer is connected ly exercised the equipment at 60Hz — but across the dummy load connected to the amp output. The oscillator level is adjust- ed to give the desired output from the

HF AC Meter amp. As with the IM analyzer, the input Level level is adjusted to give a full-scale reading Output in the "Set Level" mode. A this point, the Level Test Signal Input analyzer is switched to "Distortion," and the frequency dial is tuned to give a mini- mum meter reading. Adjust the Balance control for minimum reading. Repeat both adjustments for the best null. The Fig. 1 - Heathkit IM Analyzer reading remaining on the meter is the THD.

V A C U U M T U B E V A L L E Y IS S U E 9

25 DISTORTION A NALYZERS P A R T 2

the generator and analyzer ganged togeth- er. The oscillator output is automatically Fig. 2 - Sound Technology ACVM AC Meter Set Level o leveled, so you don't get errors when run- 1700B THD Analyzer Ratio 4, Input ning frequency response plots. The THD % THD 9 Range tester has good auto-nulling, and has a This switch closed in Ratio mode. very handy auto-level circuit that elimi- 80KHz 400Hz o - 0 — 0 Input Low-Pass High-Pass nates the need to do the "Set Level" Filter Filter Input Distortion/ adjustment each time. My particular Level Ratio Range model even had the meter calibrated to Ou put e Notch Level Filter directly read power into an 8-ohm load! Low-Distortion Sine Wave The operation of the Sound Technology Oscillator 1700B is the simplest so far: set the out- Oscillator and notch filter frequencies track 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 size, limited performance, Technology was the analyzer to have. I switch to distortion, and read out the and tedious adjustments of the 330B, I had been keeping my eye out for a used THD. IM measurements use a similar considered getting the newer H-P 331A one, but as with any desirable piece of process. As with most newer analyzers, the or 334A. The 331A/332A is functionally 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 333A/334A adds for $1200--a lot, but justifiable for my is handy in removing high-frequency an auto-nulling feature, greatly reducing audio consulting work. "junk" from the signal — which can often the tedium. The even newer 339A finally occur at the output of CD players or PC adds a built-in oscillator! However, even My new acquisition basically worked, sound cards. The 400Hz filter is good in on the used market these analyzers were but was not working to spec, and was removing hum and its harmonics 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 test bench at Pacific Stereo - and had seen a lot of hard use. Although considered obsolete for pro- The Jump to Sound Technology Fortunately, Sound Technology still exists, duction testing, the Sound Technology although at a smaller size, in Campbell, analyzers are still close to the state of the By the early 1990s, I had started doing California. I brought my unit over, and art in performance, and are very good for some serious audio consulting work on submitted it to their standard $750 over- R&D and service work. Sonny at Sound the side, and realized I needed a better haul. Judging from the number of compo- Technology told me that they still make a analyzer than the Heathkit. I had noticed nents replaced, it was more like a $3000 few 1700s for the U.S. Navy, where the that many audio professionals had a beige overhaul, but they still only charged the lack of digital circuits makes them suit- and brown box on their benches — an ana- basic rate. 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 ex-Hewlett- Packard engineers, their first product was The Sound Technology 1700B is a very Audio Meets the Computer Age a FM stereo multiplex generator. When finely-tuned, all-analog design. It is basi- their state-of-the-art distortion analyzer, cally a THD analyzer, but my model also While the Sound Technology unit has the 1700, came out in the mid-1970s, had the IM analyzer option. The residual the precision, doing frequency response their timing was perfect: the ultra-low dis- distortion is less than 0.002%. The fre- curves was tedious, and I realized that tortion wars were underway. From the late quencies are push-button selectable, with there was more to audio measurement 1970s to the late 1980s, Sound than just IM, THD, noise, and frequency response. In the search for understanding sound and and how electronics affects sound, it became clear that more different ways of looking at sound were needed. Spectrum 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 with audio in a digital form. In short, I was looking for the next level of performance in audio analysis.

The first exposure to the next level in state of the art audio testing came about six years ago when Mike Hogue, the local Audio Precision rep, gave a presentation to the Bay Area Tube Enthusiasts on their System One analyzer. This is an analog analyzer that is fully computer controlled. By using a DOS-based program running on a PC-compatible computer, the con- Hewlett Packard Type 333A Distortion Analyzer trol interface and computational features

V A C U U M T U B E V A L L E Y IS S U E 9

26 D IS T O R T I O N A N A L Y Z E R S p A R T 2

Fig. 3 - Audio Precision System Two (not including Digital Interface Test circuits) RMS 0- Det. A Input ; Level Freq. Ave. Reading Meter A Meter A Low- High- Input Phase o Bandpass/ Option Det. Meter IMD Pass Pass Auto-Ranging Meter Bandreject Filters Level Freq. Analyzer Filter Filters Filters Meter A Meter A Peak e Auto- Det. o Ranging A Inpu

Input Digital Auto-Ranging f n = 26KHz max. Input O Sine s‘, 20-bit Osc. A/D — 0 A Level A Output Digital 0 Square Wave, Analyzer Output 20-bit Burst, Noise — or A/D DSP 18-bit Generator B Level D/A B Output DSP 16-bit H . 1= 24KHz max. A IMD o 18-bi Gen. D/A fin = 80KHz max. A/D

could be updated without changing the My interest in Audio Precision was Several different high-performance A/D basic analyzer hardware. There were even whetted by my consulting work for converters are available, connected to a options for adding a DSP (Digital Signal Summit Audio, where a System One, and DSP that can perform standard analog Processor) which could do FFT spectrum later a System Two was regularly used for tests (IM, THD, noise, cross-talk, phase, analysis, multi-tone testing, and other production testing and repair of their etc.), FFT spectrum analysis, and MLS sophisticated tests. The only problem was pro-audio products. The ease of doing analysis, the latter useful for speaker test- 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-tone analysis, AES/EBU digital signal itself can be per- and digital interface analysis, were really turbed and analyzed! During the late 1970s and early 1980s, attractive. After saving up some money, Tektronix made a line of high-quality and with an assist from the booming The System Two is run from a audio test gear — most designed to fit in stock market, I decided to take the big Windows-based program, APWIN, which its DM500-series modular test equipment plunge, and get an Audio Precision gives the user separate windows for con- racks. However, as part of an MBA- System Two, complete with dual domain trolling each subsystem and function. inspired "refocusing," Tektronix dropped (analog and digital) analysis. At the time The most common method of using the their audio line. The key engineers this was written, I've had the analyzer for System Two is by running "sweeps," involved then started their own company, two weeks and am just getting familiar which generate graphs or tables of one Audio Precision, Inc. in 1986 to continue with all its power. Its capabilities are so parameter versus another. It can also do their audio work. A trend in instrumenta- extensive, that I can only cover the basic single-point measurements displayed on a tion design at that time was the incorpo- analysis functions here. In the last article, bar graph or numerical readout on the ration of microprocessors to automate some of the more advanced features will screen. Set-ups and captured data can be and calculate. However, equipment with be explained. saved to disc. All settings and commands "embedded" processors could easily available to the user are also available in a become obsolete as newer processors and The System Two 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 the tion analyzer, but with all switching and Applications (VBA). This is a fully-capa- ever-cheaper IBM-PC as their control level setting under computer control. 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. All switching and adjust- oscillator (typically 0.00003% or less at ments were done through the interface 1KHz) and an analog analysis section If this sounds like an enthusiastic mar- program. By using the computational with state variable filter and notch filter keting testimonial, it is just because I am power of the PC and its storage and with matching specs. For those who put an excited new owner! I'm sure that some printing capabilities, sweeps, graphs, and down audio transformers in a signal path, bugs and flaws will become apparent. automated test procedures could now be it is interesting to see that Audio However, I look forward to probing the done. It should be noted that the GPIB Precision uses transformers in their ana- outer limits of sound design! bus (IEEE-488), originally developed by log output stage. To provide "Dual In the next and last article on distortion Hewlett-Packard in the 1970s, allowed Domain" capability, a DSP can also pro- similar computer control and computa- vide D/A-generated analog signals as well analyzers, some typical results will be given tion, but tended to be expensive, and lit- as SPDIF (consumer), and AES/EBU torn various distortion tests. Some insights tle high-performance audio-specific hard- (pro) digital outputs of all the signals on the interpretation of the results will also ware was available for the GPIB. available from the analog section, as well be discussed. as some arbitrary and special waveforms.

V AC U U M T UBE V ALLE Y ISSUE 9

27 T H E G E N T L E G IA N T A L T E C 2 8 7 W

After the amp was up and running and a two-day burn-in complete, it was time The Gentle Giant: to reap my rewards. With close to 300 watts of thundering audio at my discre- tion, I soon discovered these amps are Altec 287 W their happiest fully loaded. They were originally auditioned on a pair of Theil CS 3.6 speakers. These were way too effi- By Natalie J. Stone © 1998 All Rights Reserved cient for an application such as this. I strapped the transformer for 5 ohms and connected a pair of old Cerwin-Vega 15 inch and 12 inch home speaker cabinets It was just over a year ago that I has a nice wide range and doesn't tax the along with my own home-brew 12 inch acquired the pair of Altec 287W ampli- driver amp. Next all the high voltage Focal cabinets. Then I set the volume up fiers. I had been reading about large tri- wiring was replaced with high-grade igni- ever so slightly as I walked down the ode amps for quite some time and having tion wire. Then the bias circuit was street to ensure my neighbors could enjoy played out several scenarios on a pair of reworked: the selenium rectifier was the music as much as I did. 1570Bs, was ready to move on. I had been talking to Sonny Goldson about Needless to say, these amps aren't for older theater equipment when he said he everyone: they like inefficient drivers and had something I might be interested in. I lots of load! They have a class B rating 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 I 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 neon lamp as an ond when it was discovered that the out- igniter and was able to develop a ten inch put transformer was shorted. 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 Amp 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 inefficient. But what a business. It didn't take long to realize that ride! They don't have the high headroom these giants had a wealth of unadulterated or presence I've heard from amps like triode power. Their circuit design was as Futterman OTLs or a Mac MI-200, but simple, if not more so, than a single- they definitely have redneck appeal. ended amp. Two things were immediately visible here. There is no feedback and One can also see the early influence RCA Type 805 li-ansmitting Triode there are no coupling capacitors. This that Western Electric had on Altec. Four leaves the input transformer - T5 - as the tubes mounted benchmark style on the most critical component. replaced with a 5A bridge and a 25 Watt- same plane, a plate current meter, and the 50 ohm pot replaced R8, allowing on-line unique starter switch that rotates. Just T5 has two jobs: first as an impedance tuning. Next, Cl was taken out and an look at the WE. 43A (VTV issue #2). matcher, 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 Altec 260A. An era was nal Altec T5 part number TL 216, so I two mods were the addition of high/low tried a dozen or so transformers until I switches on the plate and filament trans- found a Triad HSM-94. This transformer former primaries. I've seen my home line voltage swing twenty volts and didn't want to power down every time I needed to change taps.

After some power up readings were taken, I started trying different driver amps. If you are unable to track down the OEM Altec A-127 amp, a Macintosh 50W2 or A116 make good candidates. I'm currently working on building a SE/91. 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 directly, doing away with the T5 transformer. An addi- coming to a close. Gone were the days of tional secondary with common imped- the "Gentle Giants" and their simplistic ances (4, 8, 16 ohms) would allow the ways. In their place was a contorted maze user to drive speakers as well as the of RC networks, caps and coils, and 287W enough feedback to kill a concerto. The

V AC U U M T UB E V ALLE Y ISSU E 9

28 T H E G E N T L E G IA N T A LT E C 2 8 7 W

5 INPUT TERMINALS S._ O SIIMAL 105.130 0 50- SO ne OUTPUT TERMINALS Ti PRIM ART — t50 Vt. AT 1000. 700 VE .1,.. m0% .1400V SEC ONDARY 0-, 20110011 PER VOLT METER USED STRAP 5 SOURCE • - • • 1540 V. OUTPUT LOAD STRAP CONNECT- ' s! MOPED. 10000. CONNECTIONS SPECMI M IONS C.RCIA GRa

2011 to n

250 A s TO 5C0.11 E

13 °. Vo I1 A A 1112 0- 4 p.18 • 1400 • 1840V. . 08 110 A. To A A szosi.

41 070*0022 Irregse" " s 2.15 2.0511

r: 3 2[ 5 4 e PARTS LIS T 670. C I MALLORY FPS 055 .ce TO Li 02 t!. 23F3782 10 MID RS A 806 RI-St_ 'NG 10W 22000 CHIOS 123-R4 CINEMA EMS, At 1.44 OMMS R CINEMA pia. AC 140 0111/111 4111 eitbbt 8440. 40 57 014+5 ALLEN - r Orsge -8 o o Ir. 0.121 L ALTEC LANSING TYPE TI ALTEC I...9Na TYPE 00-222 TE ALTEC LANSING TYPE. 204-551 T 3 T 4 ALTE:2C =2 TYPE .754 51- St NAM 3.59011 MOMENTARTICLOSEM 11,611. 40100 U 1 218042'

PATEO LANSAS 161dITEMDIe814711 VI-VO VA U hVVIG'1"J":11 Pl1,211 1 12 .10 ASP. TO ALTED LUSSING TYPE TL 218

T A TO OP ER ATi s DATA ALTEC LANSING GAIN 2 DB POWER CUTPUT: 250 WATTS AT 5i A 287 W AMPLIFIER TOTAL NARAICNICS 54 tOM FRCCNENGV RESP S I DB 100- 000.- NUN LEVEL: -27.8 DO -20 21281. 10381-18 RENCE4 0O11...001144ATO O DBM..001 WATT

the old ways of Western Electric but can't find or afford one, you're better off any- way! And for whoever isn't afraid of super lethal power, the ALTEC 287W 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 ture than the 5U4/5R4, etc. Decide for was going in a new direction now. But yourself. At any rate the 866As weren't was it better? going anywhere. At night you can turn Natalie Stone is a vacuum tube audio the lights down with only the 287W's enthusiast who works as an electrical tech- Many have asked why I kept the two glow for illumination, put on Pink nician in a power generation plant. She 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 motorcycles, steam locomotives and problematic, but once you get a pair that would cause even the great "Harvey lately, the restoration of an original are fairly balanced, you can get several Gizmo" to make water! Linotype machine. thousand hours out of them, and besides You can reach Natalie by email: they sound better to me. A lot of people They create an atmosphere that's hard argue against mercury vapor rectification, to describe, but for anyone who enjoys [email protected]

V AC U U M T UBE V ALLE Y ISSUE 9

29 B E S T V I N T A G E H I - F I B U Y S

friend's. Tubes most likely to be weak are The Best Sounds in output and tuner tubes, but check them all anyway. Tube pins and sockets can be dirty and have caked-on dirt or scale, Vintage Hi -Fi Under especially the smaller seven and nine pin miniature types. Use a reliable and envi- ronmentally safe contact cleaner to spray into the sockets and replace and remove $350 the tube from the socket five times, then spray some more cleaner in the socket By Charles Kittleson © 1 998 All Rights Reserved before you replace the tube. This breaks up the dirt and makes a better electrical contact. Slide switches, tone and volume You don't have to spend a king's ran- for some people, so we don't recommend controls, rotary function switches and som to get a great sounding tube hi-fi this exercise for audio snobs or arrogant input jacks benefit from contact cleaner system. There are thousands of 1960's yuppies. spray as well. I have had excellent results vintage tube stereo components available with Caig D-5 spray cleaner and preserv- for a song, which may only need minor Most of the gear mentioned in the arti- ative. servicing and upgrades. The equipment cle has excellent transformers, point to Avoid plugging your equipment in mentioned in this article is not for audio- point wiring and classic, good sounding without first bringing it up slowly on a philes who must have at least 200 watts circuits. There are other good-sounding bargains out there you may know about, variable AC transformer (VAR/AC). If per channel and concert-like realism. you hear 120 cycle hum, it is most likely Obviously, those requirements will cost but the equipment listed in this article is a high-voltage filter capacitor, which the audio perfectionist ten thousand dol- common and comparatively inexpensive. must be replaced before you can safely lars or more. Components mentioned in The funny thing is, though, that when operate the unit. Any older capacitor in this article will make good music, even you start looking at a lot of the new tube the signal path can potentially effect the with moderately efficient speakers, and hi-fi equipment, much of it is copied from designs from the 1950s and 60s. sound quality of the unit. Most restorers will be easy to listen to for long periods replace them all with newer film types. In of time without listener fatigue. Plus, With all the audio equipment buy-sell publications plus rec.audio.marketplace many cases, the bias rectifier in older they won't break the bank, by costing equipment was a selenium type that goes typically less than $350US per unit (1998 and ebay.com on the Internet, it won't be bad with age and develops excessive resis- prices). They are an excellent comple- difficult to locate any one of these popu- lar components. tance. This reduces bias voltage to the ment to CD players that nearly always 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 have high Restoration can be the fun part of this diodes or a diode bridge. In addition, the frequency hearing loss and can't tell the exercise. Actually bringing a vintage electrolytic 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- It is always a good idea to obtain a CDs. ability. schematic diagram of your equipment Most audio stores will downplay the before you begin the job. Be sure to check Dynaco Stereo 70 Amplifier value and practicality of vintage compo- all wiring and solder joints. Many of these nents because many of them have never units were kits and the builder may not There are more Dynaco Stereo 70s on owned any, but mainly because they want have had soldering skills. the planet than any other tube hi fi amp to sell you a new system. New tube hi-fi ever made. The reason is simple; they are can sound good, but the price may be A lot of vintage equipment is dusty uncomplicated, easy to repair or mod and staggering. Buying vintage components from storage and may have caked on dirt. sound very musical. The ST70 was 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- removed 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, you can drive most speakers be a problem, especially if found in most small to mid-sized rooms very on chrome surfaces. Some restor- easily. The amp is nickel plated and has ers use Simichrome 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 are the to remove rust haze. Be extremely famous Dynaco A-470 Ultralinear units. careful with cleaning the dial glass For many audiophiles, 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 one You will need to check all the should be very easy. For more informa- tubes to determine if they are tion on the ST70 and other Dynaco tube strong and have no defects. Either gear, see VTV Issue #1. buy a late model mutual conduc- tance tube tester or borrow a Tube complement: two 7199s, four Dynaco Stereo 70

V A C U U M T U B E V A L L E Y IS S U E

30 B E S T V I N T A G E H I - F I B U Y S

EL34s and one 5AR4. Sound quality: sweet extended highs, due to excellent very musical midrange, bass response can transformer quality. Typical repairs: be soft and highs are not extremely replace all paper coupling and bypass detailed in stock, unrestored form. Good capacitors, replace selenium bias rectifier modifications and upgrades can improve with a silicon diode, form and/or replace the sound quality significantly. Typical all electrolytic capacitors, and replace all repairs: replace selenium bias rectifier plate and cathode resistors in the front- with silicon diodes, replace quad filter end of the amp which reduces back- capacitor, replace coupling and bypass ground hiss. Modifications include: tri- capacitors on circuit board with modern very excellent Z565 Dynaco Ultralinear ode connecting the EF86 (results in lower film types. Most mods involve replacing units that have a super-wide bandwidth. sensitivity, but cleaner sound) or replace the driver stage circuit board with a cus- All tubes and most components are EF86 with a nine-pin dual-triode, tom unit and replacing the 7199s with mounted on circuit boards that can be increase power supply capacitance, etc. more available types including 6DJ8s, kind of brittle if the unit was left on for 6GH8s or 12AX7s. Other mods improve long periods of time. the power supply with more capacitance and regulation. There were dozens of Tube complement: four 7189/6BQ5s, mods for the ST70 published in Audio two 7199s and two 12AX7s with solid- Amateur, Glass Audio, etc. state rectifier. Sound quality: musical, bal- anced and very pleasing to listen to, even when compared with higher priced com- ponent systems. Typical repairs: in most cases, the EL84 output tubes should be replaced as well as the 7199s. Coupling capacitors in this unit were very poor quality and should be replaced with newer film types. Filter capacitors should be Fisher X-101 and X-202 Amplifiers upgraded to new units. Be very careful Another popular 1960s integrated --- when working on the circuit boards to stereo amplifier series, the Fisher products avoid breakage and other damage! A were available in assembled and as kits. Dynaco PAS-3 common mod for SCA-35s is to convert Several variations were made including: the driver stage to accept easy-to-find Dynaco PAS-2 and PAS-3 Preamps X-100, X-101, X-101B, X-101C, X-202, 6U8/6GH8 tubes instead of 7199s. X-202B, X-202C, KX-100, KX-200, etc. A very popular and good sounding Most driver tubes were 12AX7s and out- stereo preamp, the Dynaco PAS is an put tubes were either 7189, 7868 or excellent choice for somebody who wants 7591. These amplifiers are full-featured, to get into a tube preamp without buying good sounding and fairly common. the farm. There are dozens of mods and upgrades published for this preamp because it is easy to work on. Most parts are mounted on circuit boards, so be care- ful when replacing caps, etc. The early Mylar and paper capacitors in the signal path should be replaced with newer film caps for the best sound.

Tube complement: four 12AX7s and one 12X4. Sound quality: a very musical pre- EICO HF 22 and HF 35 amp that can sound much better than EICO power amps are real sleepers and Fisher 400 and 500C Receivers units costing thousands. Circuit design worth checking out. They are not espe- features tone controls at the end of the Undoubtedly the most popular tube hi- cially attractive, but usually have excellent audio stage. Typical repairs: replace the fi components in the world, the Fisher circuit design and use high quality output selenium filament supply rectifier stack 400 and 500C receivers are excellent transformers from Chicago, Acrosound, with two silicon diodes and replace the sounding units. Although the output etc. Although many collectors go after two filament stage caps with newer elec- tubes are the hard to get 7868 for the 400 the higher powered HF 50 and HF 60, trolytics, plus replace old signal path and 7591 for the 500C, these receivers are the lower powered units are excellent capacitors with newer film types. Mods worth the effort. Output stage can be when properly restored. include bypassing the tone controls and modified to accept either EL34s or 6L6GCs. These receivers are still plenti- beefing up the power supply. Tube complement: HF 22 and HF 35 ful and easy to find. Transformer quality are Ultralinear type power amps with a Dynaco SCA-35 Integrated Amplifier on the Fisher stereo receivers is excellent. Mullard-Type front-end using an EF86, This iron is very musical and really makes 6SN7 and PP 6L6GC for the HF 22 or The SCA-35 integrated amp is an excel- the unit sound great. lent sounding device. Using push-pull EL34 for the HF 35. The rectifier tubes EL84s in Ultralinear mode, the SCA-35 is are either 5U4GB for the HF 22 or 5AR4 one of the most compact tube stereo amps for the HF 35. Sound quality: balanced, available. Output transformers are the with good bass, musical midrange and

V A C U U M T U B E V A L L E Y IS S U E 9

31 B E S T V I N T A G E H I - F I B U Y S

Restoration of a Fisher is not for a 48 and LK-48B; both units are very simi- beginner. These units are fairly compli- lar in styling and circuitry. The LK-48 cated, but if you have a schematic and was available with a black and champagne the right parts and test equipment, it will faceplate. be a rewarding project. Tube Complement: four EL84s, four Tube Complement: 7591A output 12AX7s, two 6BL8s (6U8s or 7199s are tubes, 12AX7s and a variety of 7 and 9 used in later models) and one 5AR4. pin tuner tubes such as 6AU6, 6HA5, Sound quality: this is a very sweet and 6CW4, etc. The 400 uses 7868 Novar detailed sounding amplifier. It is not for base output tubes. Basic repair and ser- a bass freak or a high-power nut. 222s and LT-110B. All of these units have a vice involves replacing the selenium bias make an excellent office, den or second built-in multiplex decoder and can rectifier with a newer silicon bridge, plus system for playing CDs or listening to receive stereo signals. The chassis is alu- replacing bias electrolytics. Be sure to FM. Typical repairs: replace selenium minum and wiring is point-to-point. check all tubes and replace bad ones with bias bridge with a newer silicon type. Later tuners used solid-state rectification. NOS units. If you do not have skills in Replace signal capacitors and electrolytics The Scott tuners are plentiful and cheap, FM tuner alignment, it is best to find a that test bad with newer units. Mods for so finding one shouldn't be a problem. skilled technician in you area. For more the 222 include substituting the detailed information on Fisher receivers 6U8/6BL8 driver tube to a type 7687 for Tube Complement: typical tuner tubes see VTV #6 pages 3-10. better bass and more punch. including 6AU6s, 6BQ7, 6U8s, 12AT7, 12AU7, etc. Sound quality: these Fisher FM 50 and FM 100 Tuners tuners, if properly restored and aligned, can sound great. They are less prone to Fisher tuners are the best sounding, drift than many other tuners of their era. most realistic FM tuners in their price class. Fisher really "hot-rodded" their Aligning the multiplex section can be tricky and should be done by an experi- tuners with extra IF stages and super-sen- enced professional. Typical repairs: check sitive front-ends. You don't have to buy and replace all bad tubes, replace film the FM200B or the FM1000 to get a and electrolytic capacitors, replace seleni- musical and sensitive tuner. Both the um bridge rectifier and internal signal FM5OB and the FM100B are excellent performing units. In fact, the FM100B cables with shielded silver coaxial. If the H. H. Scott 299C, D & LK-72 Amps unit you have was a kit, be sure to check was voted "best buy" in the VTV Tuner soldering joints and IF cans for damage. shoot-out in Issue #5. The early 299 Scotts used 7189 output tubes, but in 1961 the 299C was intro- Mods for tube tuners should not be Heathkit W-4M and W-5M duced with the 7591 output tube for attempted by amateurs. Amplifiers much higher output power. One of my Sherwood S-5000 & S-5500 favorite vintage hi fi pieces, the Scott Among of the most successful versions 299C has decent power, great sonics and of the Williamson amplifier ever sold, the lots of flexibility. Scott wound some of Heathkit W-4M and the later W-5M are their transformers in-house and quality of excellent tube audio bargains. They are the iron is excellent. The 299C output very easy to work on and both have tube transformers are massive and are about rectifiers. 50% larger than the Dynaco ST70 iron. Tube Complement: W-4M - two The LK-72 and LK-72B were kit versions 5881/6L6GCs, two 6SN7s and one with a few different features, but the 5V4G. W-5M - two KT66, two same basic circuit. 12AU7s, and one 5R4GY. Sound quality: Sherwood S-5500II Tube Complement: four 759 lAs, two both amps have a classic hi-fi sound, but 6U8 or 6GH8s, four 12AX7s and one the W-5M is more high-end tilted. The Sherwood integrated amplifiers are 5AR4. Sound quality: these amps have W-4M is a little more romantic sound- attractive, common and can sound good more punch than the smaller 222s. They ing. Typical repairs: replace signal and with the servicing and the right upgrades. tend to run a little warm and sound electrolytic capacitors with newer units. There are several versions of the S-5000 warm and rich. Typical repairs: replace Mods include beefing up the power sup- and S-5500 that can use: 7189s, 7591s or the selenium bridge with a newer silicon ply with more capacitance and substitut- 7868 output tubes. All of the stereo inte- type. Replacing signal and electrolytic ing EL34s for the 6L6/KT66s. grated amps have solid-state rectification. capacitors with newer units always Sherwoods have lots of controls for H. H. Scott 222 Integrated Amplifier improves performance and reliability. I phonograph fanatics including a presence usually don't recommend modding these control on some models. Variations include the original 222 that amps because there isn't a lot of extra came out in 1959. This was followed by room under the chassis. The next article in this series will cover the 222B which was introduced in 1960 mid-priced vintage tube hi-fi gear. and featured larger transformers. Then H. H. Scott 350 Tuners came the 222C which featured huge Another extremely popular FM tuner transformers and a higher power rating. with dozens of variants available. The Last of the series was the 222D with a sil- most common versions are the Scott 350, ver faceplate and different knobs. The 350B, 350C and the kit versions LT-110 Scott Kit version of this unit was the LK-

V A C U U M T U B E V A L L E Y IS S U E 9

32 M E T A L L I C R E C TIFIE RS

eventually becomes high enough to affect the circuitry. Lifetimes are highly depen- — I — Cathode Bias Metallic dent on the quality of manufacturing, but for a high-quality selenium rectifier, rated by lifetimes range from 1600 hours at 130°C Rectifiers to over 60,000 hours at 40°C. Clearly, John Atwood heat accelerates the breakdown process. 0 1998 All Rights Reserved Another peculiarity of selenium recti- fiers is, like electrolytic capacitors, their Long before modern single-crystal semi- 1920s and 1930s as car and radio lead- reverse leakage current goes up while sit- conductors became part of the electronic acid battery chargers. The low voltage per ting idle. By slowly re-applying a reverse designer's repertoire, "metallic" rectifiers cell and large sizes needed to handle any voltage, 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 found 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 not prone fiers kept a niche open for them as instru- capacitors sitting idle for the same time, to catastrophic failures as tubes are, seleni- mentation and meter rectifiers (such as so it is unlikely that reforming would 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- Selenium would be helpful to slowly apply a reverse tifiers and recommended ways of replac- voltage up to the maximum PIV (Peak The rectifying properties of selenium ing them. Inverse Voltage) rating of the rectifier. were discovered by Werner Siemens in Copper Oxide 1877, but the first commercial selenium The most insidious problem with seleni- rectifiers did not appear until 1928 in um rectifiers is their potential for emitting The earliest commercial metallic 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 rectifier to overheat, it will cre- takes place at the boundary of Cuprous and during World War II, and after the ate selenium vapor, which is poisonous. If Oxide (Cu02) 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--clear copper-cuprous oxide junction is typically Selenium was popular because the break- everyone out 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" are stacked in series. In "stacks" much smaller and more efficient facturers' literature, but was well known higher-power rectifiers, the plates are than copper oxide types. in the radio-TV service community. arranged as fins to permit air cooling. For the first year or so of use, the forward The dark side of selenium rectifiers is Other Metallic Rectifiers voltage drop increases as the copper oxide their instability over time and their ten- 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 sele- stable. peratures. For general-purpose bulk recti- fication, things like unstable reverse cur- nium rectifiers. Several problems have Along with Tungar gas rectifiers, copper rents are not a problem. However, the for- kept this type from gaining popularity: a 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 reverse Typical Selenium Rectifiers voltage of about 5 volts per cell, and a much shorter life-time than selenium.

Titanium dioxide rectifiers, made by applying bismuth to a layer of titanium dioxide built up on metallic titanium, were developed by Battelle Memorial Institute in an effort to create very high temperature rectifiers. They could func- tion at well over 300°C, and up to a point, their characteristics get better with higher temperature. They have fairly high leakage current, and a maximum reverse voltage of from 5 to 15 volts per cell.

Co ming in VTV#10 6V6 Shootout, Tube Headphone Preamp project, and More.

V A C U U M T U B E V A L L E Y IS S U E 9

33 M E T A L L I C R E C TIFIE RS

Although not considered in the same for selenium. In cases where the DC volt- There has been some concern about family as selenium rectifiers today, germa- age is regulated or can be adjusted, such as whether the original selenium rectifier can nium and silicon rectifiers were grouped with the bias rectifier in Dynaco power be kept in the circuit. If you simply wire with metallic rectifiers in the 1950s. amps, there is no problem, and no other silicon rectifiers across the terminals of a Germanium alloy-junction rectifiers were precautions are needed. In cases where selenium rectifier, virtually all the forward the first commercial power rectifiers built there is no regulation and the DC voltage current will flow through the silicon, using the single-crystal technology devel- is critical, such as in DC filament sup- bypassing the selenium. This bypassing oped for transistors, and were first avail- plies, series resistance should be added to technique is convenient, since the old rec- able about 1950. Germanium rectifiers bring the DC voltage to the correct value. tifier acts as a terminal strip for the silicon have a very low forward voltage drop — This value should be determined from the rectifiers. However, there have been about .2 to .4 volts, high breakdown volt- manufacturer's documentation, since the reports of seleniums burning-out due to age (up to 300 volts), and reasonably low value measured with the existing selenium reverse current, so for safety, the selenium reverse leakage current. Their main limita- rectifier is likely to be low. If there is no should not be connected to the circuit. documentation, an estimate can be made tions are: limited high temperature opera- Using the techniques described above, based on the circuit usage. For example, tion of 85°C maximum, and the need for you can maintain equipment using metal- strict hermetic sealing. Germanium power tube filament supplies are generally multi- lic rectifiers indefinitely. rectifiers were used by industry and the ples of 6.3 volts. Many pre-amps that use military, but were too expensive for con- low plate-current tubes, such as 12AX7s, Bibliography sumer use. will run the filaments at lower voltages (from 5.0 to 6.0 volts) to reduce noise and 1. Metallic Rectifier and Crystal The first silicon power rectifiers were increase life. Diodes, T. Conti, John F. Rider, New alloy-junction types, similar in construc- York, 1958. The best way to pick a series dropping tion to germanium rectifiers, and were 2. Selection and Application of Metallic resistor is by cut-and-try, since there is no commercially available in the early 1950s. Rectifiers, S. P. Jackson, McGraw Hill, easy analytical way to characterize the cur- They improved upon germanium rectifiers New York, 1957. by having extremely low leakage, high rent pulses in a capacitor-input rectifier maximum operating temperature (150°C) circuit. Either have a handful of low- 3. Power Rectifiers with Notes on and breakdown voltages up to 1000 volts, ohmage power resistors or have a power Converting Machinery, J. Rosslyn, although they have slightly higher forward rheostat, and substitute resistors until the George Newnes Ltd, London, 1941. DC voltage is correct. Make sure the AC voltage drop (approximately. .7V). In 4. Testing and Replacing Selenium power line voltage is at a known nominal 1956, commercial diffused-junction sili- Rectifiers, D. Schoo, Antique Radio value (generally 120 volts in North con rectifiers became available, bringing Classified, Sept. 1997, pp. 18-23. better control of characteristics and much America) when doing this. Pick a power better electrical ruggedness. Later, silicon- rating so that the resistor does not run too dioxide passivation was added to allow hot. As an example, when the selenium packaging in non-hermetic packages. This bridge rectifier in a Fisher 500C receiver is basically the same construction as the was replaced, it was ubiquitous 1N4000-series of rectifiers so found that a 4.71-2 5 watt common today. resistor was needed to bring the voltage within Dealing with Selenium Rectifiers spec.

In electronic equipment that uses metal- The voltage rating of a lic rectifiers, selenium is by far the most replacement 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 refurbishing a piece of vintage equipment selenium rectifier, or by that uses selenium rectifiers, a decision the AC voltage used in needs to be made on whether to stay with the circuit. Using the selenium, or to replace with silicon types. plate method, allocate 25 If historical accuracy is desired and the volts per plate (between equipment is not heavily used, then stay- terminals), and multiply ing with selenium makes sense. If the by 2 as a safety factor. original rectifiers are weak, as determined Using the AC voltage by low DC output voltage, then they can method, take the AC be replaced by either a selenium rectifier voltage presented to the removed from other equipment or by an rectifier, and multiply by unused N.O.S. replacement. On the other 2.83 for half-wave and hand, if just functionality and reliability center-tapped full-wave are desired, then the seleniums should be circuits or by 1.41 for replaced by silicon rectifiers. However, sili- full-wave bridge circuits. con types cannot just be substituted with- Then take this resulting lntruduu out some thought on their usage in the peak voltage, and multi- The Ultimate Dynamic circuit. ply it by 1.5 to 2 to give a safety factor. Remember, Headphone Amplifier. Because of the lower voltage drop of sil- you can always use a icon rectifiers, the rectified DC output Ri-Fi Show 98 Westin Hotel suite 976 higher-than-necessary voltage will rise when silicon is substituted (213) 467-4300 voltage rating.

V A C U U M T U B E V A L L E Y IS S U E 9

3 40 Its Like Music to Your Ears... Amperex Bugle Boy audio tubes are back and they're better than ever!

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 voltages applied for 24 hours before being tested for noise Et microphonics. The aging racks 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 (THD). The THD measurement is performed using one of the finest spectrum analyzers available — the Hewlett Packard 3561A. Matching in pairs, quartets 8- octets is available for all tube types.

Special test requirements? Not a problem. For a slight additional charge we will test and match to your specified operating conditions.

Types available: 6DJ8/ECC88, 12AU7A/ECC82, 12AX7A/ECC83 and, many more!

So if you haven't dealt with a source capable of meeting your demands, call us at 1-800-TUBE USA or 630-208-2200 today for information on additional products and the worldwide locations nearest to you. You'll like what you hear!

APD is pleased to announce BLUENOTE Midas Dampers are the addition of Ham mond LI now available, along with other Manufacturing's complete line quality audio accessories - of Classic Transformers and Thinking such as, equipment isolators Enclosures to our product about building and CD/LP treatments. The Midas Dampers (as reviewed in offering. Call today for a your own Ham mond catalog or down Stereophile Magazine, February, amplifier? load it from our WEB site at 1996) are made of the highest Call 1-800- w w w.tubes-r-us.co m/ quality materials available. classic.html. TUBE USA They reduce microphonics in your preamp tubes thereby enhancing the music you hear.

Call 1-800-TUBE USA or 1-800-882-3872 today for your copy of our NEW APD brochure featuring Audio Tubes, BLUENOTE and Ham mond products.

Richardson A, p Audio Product Division Electronics, Ltd. a division of Richardson Electronics, Ltd. IS09002 Registered 40W267 Keslinger Road You can also visit our Classic Components P.O. Box 393 site on the Internet at: LaFox, IL 60147-0393 (630) 208-2200 http://www.tubes-r-us.com (800) 882-3872

35 Though Heath-kits, Knight-kits and Eico-kits are gone... still the Incredible Sound of the 50's is back!

Easy-to-ht. ild Tube HiFi Stereo

Kits Made In USA

Model Description Assembled Kit Chrome each each add-on

A-1 Amplifier 10 Watt Mono Block, 2 x EL-84 P-P $ 299 $ 229 $ 60

A-2 Amplifier 10 Watt Stereo, 4 x EL-84 P-P $ 435 S 349 $ 80

A-4 Amplifier 30 Watt Stero, 4 x EL-34 P-P $ 559 $ 449 $ 95

A-8 Amplifier 80 Watt Mono Block, 2 x 6146B P-P S 1195 S 995 $ 120

PP-1 Phono Pre-Amp, Stereo with Gain control, 40dB gain $ 439 $ 329 $ 50

PP-2 Phone Pre-Amp, Stereo with Gain control, 60dB gain $ 525 5 395 $ 60

PA-1 Line Pre-Amp, Stereo with Gain, Balance, Treble, Bass $ 699 $ 579 $ N/A

PA-2 Line Pre-Amp, Stereo with Gain, Balance, 5 inputs $ 625 $ 499 $ N/A

PA-12 P/A Amplifier 12 Watt Mono, with paging $ 389 $ 299 $ 60

Prices for protective cages: A-1 & PA-12 = $39, A-2 = $77, A-4 = $89, A-8 = $99, PP-2 = $45

Call for your free Catalog now!

Many Models: Amplifiers * Preamplifiers * Phono Preamps Documentation: Complete easy step-by-step Assembly Manual

ASUSA-Kit E-Mail: [email protected] 6717 NE 181' Street, Seattle, WA 98155 USA Phone 425-481-8866 Fax 425-485-3836

36 This i:, „.• >music lover's speaker -

the &tern:7 - is brought closer to the tit hsloal ilrrough the window of the A /ix-Anne II. There is a seamless integration of the voice of the speaker which leaves the impression of a single peifect driver - no part of the spectrum is favored over another It has the agility to accurately recreate the transient nature of a piano, a plucked string or a struck instrument. At the same time, it lacks any sign of stored energy of its own so that the natural modulated decay of an instrument sinks into silent blackness in proper time. Another important characteristic is that the speaker neither diminishes nor exaggerates the scale and size of a musical

96 dB SPL 2.83v/ 1 meter sensitivity in a true instrument or voice. This is a rare transducer utilizing a patented, pure first order, compli- accomplishment in a speaker mentary symmetry crossover. Suitable for solid state amps system. The Aliv-Anne II brings to 300WPC: or experience the magic of uncompromised r:. performance with the SE 300B. The stable resistive load the performance to the listener and that the Alix-Anne II presents to a single ended amplifier then disajeais su that the results in a near perfect match. connection of ,..er tu Designed for operation on or in the the wall pressure zone, performing ci fist is dire(,. this wall-mounted speaker uses zero floor space. Dimensions: 37" x 14.25" x 3.875"

Constructed of beautiful, solid, non-endangered hard woods. A MERIC A N APPLIED AC OUSTICS under license from American Power and Light, Inc. Dealer Inquiries invited Phone: 916.666.1873 Suggested Retail Price $3,995.00 per pair Fax: 916.666.6272

37 A LEGEND REBORN! The legendary British made KT66 is one of the most Enlarged, heavy gauge figured glass bottle 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 Fi amps and the first Marshall Extra thick premium quality star mica guitar amps. This tube was spacers (top and Bottom) improves ." performance stability and reduces the sound of Eric Clapton on adverse microphonics. the classic John Mayan Bluesbreakers album. Precisely tensioned filaments for better mechanical stability and If you can even find an orig- reduced adverse microphonics. inal KT66 today, they'll set Deep 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 Brite nickel beam focusing elec- new life to this legend, trode concentrates the electron creating our own tooling to flow precisely on the plate for 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 musical parameters no other All specifications equal or tube maker even knows about. exceed the original Genelex Gold Lion la66 standards. Groove Tubes is offering Performance Matched Duets of the GT-KT66R @ $120 (U.S. retail price).

Groove Tubes...The American Tube Company, since 1979. 12866 Foothill Blvd., Sylmar California 91342 USA Tel: (818) 361-4500 • Fax: (818) 365-9884 • www.groovetubes.com

38 ur tpor5 of "(Cage' Zran5tornitre Sc (Enttee m

Single Ended, Push-Pull and Potted Tube Output Filter Chokes Transformers

Aluminum & Steel Chassis and Diecast Aluminum Enclosurés e Open & Enclosed Filament Transformers High Voltage Plate Transformers

Contact us for a free catalog & list of stocking distributors

4700 Genesee St..- Cheektowaga, NY 14225 USA Phone: (716) 631-5700 Fax: (716) 631-1156

394 Edinburgh Rd., N. 7 Guelph, Ontario N1H 1E5 Canada Phone: (519) 822-2960 Fax: (519) 822-0715 •-www.harnmondmfg.com We are a proud dealer of Western Electric Audio Products. The current production 300B is now in stock. Ele lye Electron Valve stocks a wide array of NOS Vintage Audio Tubes like Mullard EL34, RCA 2A3, and Mullard 5AR4. We also have a good stock of Old Production Your source for hard to find Western Electric tubes such as 205B/D, 252A, 274B, 300B and many others. ••1 Vintage 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 Components Modjeski. We also carry the Music Reference M q RM-10 (Push-Pull 6BQ5, 35W/Side) Stereo Amplifier and the

Stop by our website to see a detailed look at all of our products! Music Reference RM-200 (Push-Pull 6550, www.electron-valve.com • Email: [email protected] . 100W/Side) Stereo Amplifier. Phone: 901-382-9955 • Fax: 901-382-9956 .--

VV •V,

lam

VV300B clèa, $4 5.00/pr The KR Enterprise VV Valves are the first new directly VV300B blue $575.00/pr heated triodes to be manufactured in aver three decades. , P VV302BC br ' 575.00/pr Hand built in the Czech Republic witll their patented 32 cla el $6$5:00/pr cathode and ribbon filament structure, the VV Valves VV3213 clear-' 7 i.DO/pr will provide more power, lower distortion and better tonal VV52B fidelity than 'S available with any other power triode.

For more information contact the North American Distributor:' "- -

‘Atelborne Labs P.O. Box 260198 Littleton, CO 80126 USA Voice: 303.470.6585 Fax'. 303.791.5783 e71111a'il lab @-ix.netcom.com

OEM and dealer inqu' iries invited. The VV Valves aré \,-Zrarranted fOr one-year or 2000 hours. . — - - Listen to the VV Valves today and experience a whole newhotizifn -of musical pleasure.

40 . - 205-8821311 Fax -205-1-38M077 • Mar.koling & fnoinetirinn: 3000 Mole 181 Pondia Va.!ley, CA 91028 -Phone 650-233-042 .9 fax 0!-i0 233=-0139 Books, Goodies, Itt Subscriptions

N TAG E VTV #1 Spring 1995 $8 US - $10 Foreign Vintage Hi-Fi Spotter's Guide-Volume 1 V Vintage Dynaco Tube Equipment - 1955-77 Over 450 photos & specifications of tube audio gear

History and Testing of the 12AX7/ECC83 dual triode from the Golden Age of Hi Fi. 86 pp. $18.95 SPOTTER'S GUIDE Tube Testing Methods + Early Amplification and Amps Vintage Hi-Fi Spotter's Guide Volume 2 g i g e VTV #2 Fall 1995 $12 US - $15 Foreign Volume 2 covers equipment not listed in Volume 1. Almost 500 amps, preamps, tuners, etc are depicted. Heathkit - The Tube Williamson Years 1950-61 VI NTAGE Edition covers early audio and includes a Speaker section EL34/6CA7 History, Types and Tests

with most vintage manufacturers. 88 pp. $18.95 W e Magnum SE EL509 Amplifier Project by Dave Wolze e SPOTTER'S GUIDE 1927-34 Western Electric Theater Sound Systems Vintage Hi-Fi and Pro Audio Price Guide

Updated price & grading guide for almost 1,000 vintage 1Fi g VTV #3 Winter 1995/96 $12 US - $15 Foreign vArut ILLLI hi fi amps, preamps and tuners. Includes Vintage pro Eico Mono Tube Gear - 1955-62

audio and theater gear. Also, pro loudspeakers, N.O.S. VENTAGE HATI Altec Lansing 604 Coaxial History PRICE GUIDE vacuum tubes and audio transformers. $30.00 Western Electric 300B History and Listening Tests A 300B SE Transformer Listening Tests "Vintage Hi-Fi The Golden Era Video" VTV #4 Spring 1996 $12 US - $15 Foreign A one-of-a kind video covering the classic post-war and 6L6 History, Types and Listening Tests 1950s home hi fi era. Over 80 classic audio amps, pre- amps tuners, are shown. This video is professionally pro- Vintage Bookshelf Speakers 1955-1965 duced. 34 min VHS NTSC $25.00 Early FM Broadcasting History HK Citation I & II Amplifier History and Mods The Ultimate Tube Substitution Guide

VTV #5 Fall 1996 $12 US - $15 Foreign No tube electronics enthusiast should be without this book. Over 10,000 tubes are listed on 240 pages includ- The Ultimate FM Tuner Shoot Out ing: audio, radio, transmitting, and special. Features an Red Bank Guided Missle Tubes for Hi-Fi The Birth of the Maranta 10B audio tube section with tube evaluation. $29.95 Choosing Rectifier Tubes for your Guitar Amplifier rorie, Vacuum Tube Valley T-Shirts VTV #6 Winter 1997 $12 US - $15 Foreign Two Styles to Choose From! Fisher 500 - History, Models and Restoration A Tribute to Avery Fisher by the Fisher Doctor A) VTV Marching Tubes -"Big Tone" 1 sided available in several colors. 6550 and KT88 History, Types and Listening Tests VACUUM TUBE VALLEY mirarsche micis m = Tan, Sea Foam Green, and Burgundy $15.00 XL only Loftin-White Amplifier History by Alan Douglas B) VTV Tube Sunburst Shirt with 2-color black & orange VTV #7 Summer 1997 $12 US - $15 Foreign art as pictured plus large 2-color RCA tube diagram 6DJ8 & Frame Grid Tubes + Listening Tests _vacturi rtibé valley— exploded view on back. (white or gray) $20.00 XL only Altec 1950s Theater Amps and Modifications Sureeyvale, Calrf. USA The Great Voice - The Peter Jensen Story w fflysyactutembextem Computing with Tubes - The Savage Art Uncle Eric's Tube Dumpster - 417A/5842 VTV Politically Correct Bumper Sticker two-color waterproof vinyl 212x 10" VTV #8 Fall 1997 $12 US - $15 Foreign Sent post-paid: $3.50 US - $4.50 Foreign EL84 History, Types & Listening Tests RCA Tube Mfg at Harrison, New Jersey Quotes from VTV Subscribers: 200 watt OTL Amp Project by Allan Kimmel "The best audio mag on the planet." "Clearly written with great photographs." 300B Listening Tests: NOS and Vintage Types "A wealth of vacuum tube information." "1/TV reads with authority and truth..." Bruce Moore Tube Audio Pioneer

Name Date Subscribe To Vacuum Tube Valley The Classic Electronics Journal Address City State Zip $36/year US - 4 issues $43/Canada, Please Send Me The Following Products $56/Europe & $66/Asia & World

VACUU M TUBE VALLEY 1095 E. Duane Ave Ste.106 Add $5.00 Shipping per order in USA /Add $ 10.00 - Item Air Mail Foreign Shipping $ Sunnyvale, CA 94086 USA CA Residents Add 7.75% State Sales Tax (CA Tax) 408-733-6146 Phone Credit Cards, U.S. Bank Checks or Money Orders OK TOTAL ORDER $ 650-654-2065 FAX email - [email protected] Credit Card # Exp. Date w w w.vácuunitube.com Signature Western Electric High.Fidelity

Matched Pair WE300B

Weden‘ eerie Fldeley psochech ore snorkeled worldescle by Werre Corporally^ n Elearic a a belt...irk of lucent Technologies Inc, Western Electric Audio Products formeriyAT&I , Inc., licensed Pq Wash.° x Carp , o compoPy ihetependent oi Lucent ts of 8*/ iatoratones Wesicm &chic 1230 Peachtree Street • Suite 3750 • Monts, GA 30309-3575 0(404) 874-4400 lax (404) 874-4415 High Fciedity products creams/rodeos! JO then( SA e-reaii: [email protected] • Internet. w,env.westemelectric.corri -