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2AX7 Special Edition Uriwunclb TM 2AX 7 Special Edition uriWunclb MooDoe tUdlOck3 MêEbOn, CD Player with a Glass Hear Sâ:? ULIDU G ? V k; U7 The Acrosound Years .7ectedocurd TRANSFORMER ACRO PRODUCTS CO PHILA_ PA, TYPE Visit us on the web www.vocuumtube.com ISSUE 14 64 P.O. Solc1499,1-olcepott, CA 95453 USA Phone Ç707) 1.63-5881 fle. V/07) 9.63-'1 11 http-.1 Iverre.vocuuneube.com February 17,1999 lee Nett\14er/ lees Sensor Corporation Seek/ NYC,11-,anks e( ogám For seeng us 'ne new l'2.PY,71.1) tubes For evaluation. \rINI conducted bot'n listening and electri- Dear I\K‘ke, lol-m Atwood, \11\11ech etor, took \Fe 1 71-F's to his One Electron 10boratory and used a lektroriix 570 col curyetests otracern tlie to tube,evaluate tl-e tulods elect6col characteristics. lo'nn noted that the tube is Yery Vmeor ondlios great look:mg curies, indicating a well-mode tube. Compared to the Seek 12.PJ(7s oF %lie post, he Felt that your new tube is d‘gretcantly better. in Fact, John commented fret its cviality approaches the Famed leinken llext, see gave t'ne 12..PY,7 es to Roger Coon, e1\ -known record collector and 0 md\or audeph‘le in the Son E.CC83Fronetsco smooth boy plate.Issrea. Roger is a Yery critical listener and has "golden eors ,'' plus, \-%e recently completed o , 1.2.el listening test For co Future issue 04 vri. Fie notes.. "large, Full soundstoge, very musical with r;ice deto.' \--ie compared it to the sound .:: a Mulled C\I b004 box plate 1?..P.Y.7 , but not quite os deteed. in sl-ert, Roger 11-en \listened to t'ne 12.0.71-9 in o variety OE tube prearnOers and arm:4\es. `(oul-eve a vert musical, seas se`99\‘,impressed ond\ro9W\1101‘)\De• NY* your tube. \‘ \s ectsY ‘0 \\stet\ \c, 't)," \ 0119 Pel-\08s c:. t\rne, \\\Çe o cie\\Y/ tube s\lou\à be. 1\1\ s will be a (eat tube For both hi-Fi and guitar amp opp1\ cations. i enk it sounds a lot like o vintage brimor Compared to anything else out t'nere in t'ne 12.11)(7 market, %rib t'ne exception o1 some primo NOS stuFF,i Feel t1-tot the SoYtek121s)(71.? is the best sounding one on the market ot es time. in conclusion, you 'nosie a Yqinner l'ese . \\eel "(hanks again and best regards. NEW SENSOR CORPORATION 20 COOPER SQUARE NEW YORK CITY, NY 10003 FAX (212)529-0486 [email protected] WWW.SOVTEK.COM E D I T P A G E A N D I N D U S T R Y N E W S Western Amplification and Tube No More 6922s & 7308s Technology Society to Form VTV Issue # 14 There is now a severe shortage of NOS quality 6922s and 7308s. The Table of Contents: A new society, (WATTS), dedicated to the advancement and enjoyment of sole source of new 6922s is Sovtek. vacuum tube amplification is forming This tube, while noted for its reliabili- in Northern California. Its sole pur- ty and low microphonics, has some 12AX7 Twin Triodes 4 pose will be to provide a forum for sonic deficiencies. builders, listeners, manufacturers and 12AX7 Listening Test 9 VTV recommends that OEMs technicians interested in tube amplifi- should change their circuit designs or cation of music. Nominal annual dues The Gillum G3 Speaker 17 that they pay the development costs to will be collected from members who a tube manufacturer for a better 6922. PP 5V83 Amplifier Project 18 will have access to association meetings End users have an option to modify and events. Non-members will be wel- their equipment to accept better tubes David Hafler Interview 20 come, but will be subject to entrance that are available for less money. This fees. Direct Reactance Amp 25 includes the 6N1P (still being made). The group will have structured quar- Plentiful and still cheap NOS tubes Jolida JD-603A CD Player-27 terly meetings, held on Sunday after- that are still suitable for audio include: noons and consist of a general session 2C51/5670, 5687, 6021, 5963, 5965, Internet Lies and Hype 29 and other tube events. These events 6385 and 6350. Dumpster 7 Pin Pentodes 31 may include: tube product demos, tube and amplifier listening sessions, New 300B from Electro-Harmonix Advertisers 33 amp clinics, guest speakers and a bi- The new 300B EH has an improved annual tube swap meet. A survey will grid, eight course directly heated fila- be taken to determine future meeting ment, 40 watt plate dissipation and Coming In the Next topics and group structure. excellent stability. This improved tube has top-quality construction and ultra- The initial kickoff meeting will be Issue of VTV: long life. The attractive tube now has held at Sunset Car Audio, 1701 Santa a ceramic base and is available singly Rosa Ave., Santa Rosa, CA. (Baker or in matched pairs. Suggested retail Ave. exit Northbound on Rt. 101) on • David Hafler Part Il price is $156 per tube. October 15, 2000 from 1PM to • 9-Pin Dumpster 4PM. For more information contact Electro- Pentodes Meeting details will be announced on Harmonix: Phone (212) 529-0466; www.vacuumtube.com. Please do not FAX (212) 529-0486; www.ehx.com • Assemblage SE 300B call or email us as we will not take tele- Review phone or Internet inquiries. VTV Subscription Rate Increase • 12AX7 Hi-Fi Listening The cover price of individual copies And More! of Vacuum Tube Valley will increase from $9.00 per issue to $10.95 per issue, effective with Issue #14. Cool NOS Tubes at the: Subscription rates will increase from VTV Pro-Tube Shop $36 to $40 for 3rd class and $49 for 3 00 B Eli www.vacuumtube.com First Class US, $52 for Canada, tornenix: $60/Europe and $68/Asia/World. !Ill New 300B EH EDITORIAL STAFF Vacuum Tube Valley is published quarterly Copyright 2000 Vacuum Tube VolleyTM for electronic enthusiasts interested in the All rights reserved. colorful past, present and future of vacuum Charles Kittleson - Editor in Chief No part of this publication may be reprinted tube electronics. John Atwood - Technical Editor or otherwise reproduced in any way without written permission of the publisher. Subscription Rate: US$40/4 issues 3rd Class-$49 Eric Barbour - Senior Editor Send circulation and editorial 1st Class; Canada/$52; Asia/$68; Europe/$60 Ron Veil - Guitar Amp Tech Editor correspondence to: David Bardes - Product Reviewer US Bank Check, Credit Cards or Cash Vacuum Tube Valley are accepted for payment. Steve Parr - Art Director RO. Box 1499, Julie P. Werner - Copy Editor Lakeport, CA 95453 USA Phone - (707) 263 - 5881 e-mail [email protected] FAX - (707) 263 - 6724 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 1 4 2 A X i : T W I N T R I O D E S F O R E V E R made to very high standards, and bear high NOS prices today. Such tubes often 1 2AX7: Twin came with molded plastic protectors stuck over their pins, to keep them from 8 K2 being bent in shipment. The presence of Triodes Forever such a pin-holder is a sign of a genuine By Eric Barbour '2000 All Rights Reserved 9A HM classic Mullard or Brimar tube, or of a top-quality MOD item. Production of This article is intended to serve as an update for the such tubes ceased in the 1970s. The pin 12AX7 summary which appeared in VTV #1 back in May protector was revived recently by Richardson Electronics for their costly "Bugle Boy" brand. 1995. History Update One problem with 12AX7 types has always been micro- phonics, especially in avionics and instrumentation (where It has been confirmed that the 12AX7 was introduced microphony could cause death or injury). Telefunken simultaneously by RCA and Sylvania in March 1948. solved this in 1958 by introducing a unique tube, the Sylvania was probably the sole manufacturer at the time, ECC803S. Unlike all other 12AX7s, it used a type of grid with RCA being the engineering developer. This was a construction used on RF preamp tubes such as the 6DJ8-- commonplace arrangement until the 1980s--many "RCA" the so-called frame grid. Rather than winding ordinary tubes were engineered by RCA, but were actually manufactured by Amperex ECC83/12AX7 Plate Curves Sylvania or GE under contract. 5 12AU7, the medium-mu variant, was introduced simultaneously, and used mostly common parts except for the 4 A M R a% 4 >e) i_o grid (yes, that's right--not much r: physical difference except in the grid < • windings!). These two dual triodes • ., became the most popular electronic 3 MMMMMM amplifiers of their period. For exam- ple, the Philbrick Researches Inc. 44 K2W of 1952 was the first really suc- 1N32:1111 MMMM UMMA cessful operational amplifier on the Mg market. It used two 12AX7s. M Br: MgdOMMIN Most audio equipment after 1956 A M BB 4ommm my g4 used 12AX7s as gain devices, in pref- UMW Manar 4 PP M 4OMME UMMgo • MMMMMMMMM ,i al:mmmeg MM M 50 Ma erence to the previous heavy use of MMMMM MM UP m 4g ...41MBORBP .- pentodes like the 6SJ7 or octal dual _.e .rnams triodes like the 6SL7GT and O MMMMM MMM le M 6SN7GT. Famous pro-audio prod- 50 100 50 200 250 300 350 ucts, such as Pultec and Teletronix PLATE VOLTS processors and the Ampex 351 tape recorder, relied on 12AX7s.
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