o D 6550jKT88 The Power Kings 000®�00� Guitar and Hi·Fi Best Bets Visit us on the web _.vacuumtube.com My darling, wi1J yoU ever leave me again? D a -Svetlana The finest audio power tubes in the world are available again in the us and Canada, exclusively from PM of America, Inc. Svetlana www.svetlanausa.com ------------------------------------- PM 1687 Shelhy Oaks Drive I Suite 8/ Memphis, TN 38134/901-388-24241 fax 901-388-2405 �._- ------------------------------------------------- • D , 0 • 5 It A G I AND NDUS,RY N I W I New Tubes from Sophia Electric Riccardo KIon Dies at G8 VTV Issue 19 As fo under and owner of KR Sophia Electric has recently inrro� Table of Contents: duced three new tubes aimed squarely Audio, Riccardo believed in cube at vacuum tube audio enthusiasts. [echnology and in its development as 6550/KT88 Power Kings••••••• 4 Encased in a retro globe-shaped bor­ the fu ture of sound reproduction in de, the 300B and 2A3 are idemical in audio. His designs and projects are Contest for High fidelity 11.. ... 9 construction, and only the designa­ the basis for the technological legacy he left at KR Audio Electronics in NOS Tubes Sound Better.. ....14 tion of the filament voltage on the base reveals the difference. The 274B Prague, Czech Republic. is also a lobe botde', but has conven­ KJipsch Rf-7 Speakers ... ..17 g Kron designed a low COSt television tional solid plares for its dual diodes. known as the "engineering miracle" in Beming Mino ZOTL Amp ....19 dle 1960s. He is most remembered Craftsmen C 500 Amps ....... 21 fo r his award winning design of the Kronzilla tube, the KRT- 1610. the Ecklond KT88 Amp Project .. 26 largest audio tube in production, and for the "Best Sound of the Show" 6550 Shoot Out Hi fi .......... 28 prize awarded [Q him for the Kronzilla double monoblock amplifi­ 6550 Shoot Out Guitor........ 32 er at the Frankfurt High End Hi-Fi Fair in May 2002. vrvVisits the NAMM Show 2003 Bay Area Tube Fest June I, 2003 These mbes are the finishing touch In i:.ueJanuary 2003, we visited the The second annual Bay Area Tube to that retro looking amp project. The Festival is being held at the Randall famed NAMM show in Anaheim, globe bortle conjures up the pioneer CA. There were dozens of tube amp Museum in San Francisco on June I days of audio, and the glow of the fil­ from 9AM to 6PM. guitar companies, distributors and aments through the mesh plates is even tube manufacturers including very cool. They look great! The all-day event will include pre­ JJ of Slovakia. sentations by: John Arwood, who will I placed a pair of the 300Bs in my discuss audio spectrum analyzers; Alan We met with many of our vendors SE am and they proved to be very p Kimmcl, who will present his choke and customers fa ce-ta-face and had a musical. They possess a wonderful mu stage amplifier; Gary Pimm, who great rime. See our wehsite under open and sweet treble that is the best will review AC current circuit analysis; Hot News" fo r color photos of the I've heard in my living room. With Lynn Olson. who will discuss amp­ likes of Mike Manhcws, Noreen these tubes in place, cymbal strikes speaker interface; and Jack Elliano, Cravener, Ralph Trimarchi, erc. were clear, real and decayed exquis­ who will cover his SE and PP amp itely. Midrange response was firm and In addition, we were treated ro a designs. grand tour of Aspen Pittman's detailed. Bass response was solid, but Groove Tubes operation in San the Sophia's didn T dig as deep as some Vendor tables fo r tubes, pans and Fernando. I-le is now in production other 300B tubes I've listened to. equipment wil! be available at the making the reissue GE 6LGGC out­ Seill, the Sophias arc detailed, reveal­ event. Beverages and sandwiches will pur tube. They are planning a fat ing and warm, and while not as be served on-site. bottle EL34 and a 6VGGT as well. punchy and dynamic as the Sovtek or Admission is $15, payable aT the We are planning an extensive s[Qry JJ 300Bs. are a delight to listen to. door. For more information, contact on Groove Tubes and their bourique or Phone: 703-204-1429 571-277- Chris Betcher 3[ 415-554-9601. power mbe manufacmring in VTV 8823 www.sophiaelectric.com Check the vrvwebsitc for more info. #20. Stay mned!!! Editorial Staff Vacuum Tube Valley· is published quarterly Copyrig,t 2003 Vacuum Tube Valley· lor electronic enthusiasts interested in the color· All rights re!oerved. Charles Kittleson Edilor and Publisher ful post, present ond future of vacuum tube No port of this fX'blica�on may be reprinted Eric Barbour Senior Editor electronics. or electronically reproduced without written Lynn Olson Technical Editor permission 01 the publisher. Sub$Criplions: US$45/4 inue� 3rd Ckm·$55 Ron Veil Guitor Amp Tech Editor Send circulation and editorial I sI C!an; Canoda/$60; A.!ia/S75; Europe/S70 David Bardes Associote Edito( correspondence to: US Bank Check, Credit Cards or Cash Sieve Parr ArtDi(ecto( Vacuum Tube Valley are accepted forpayment. P.O. Box 1499, Werner Edito( Julie P. Copy lakeport,CA 95453 USA phone (707) 263 - 5881 V",I uS on I t... web! e·mail [email protected] FAX (707) 263 - 7648 ISSN # 1095-4805 www.vocuumtube.com VAC UUM TUBI VA LLIY ISSUI 19 I' 6 5 5 0 / K , 8 • • I v • , I D 6550/KT88 Power Kings Part 11 By Eric Barbour °2002 All Rights Reserved 1. lntro The concept that a ower tube wc U� today was made ,r "without compromise amuses me to no end. Since our previous 6550/KT88 article in 1996, many morc fac(S about the origin of these �poplllar" types has come ro light. Some of the facts seem to contradict the commonly­ nmg-Sol6550 (1963triple ge tter-IIO holeswith GE mark­ held audiophile snobbery surrounding these tubes··espe­ i1lgs) aminmg-SoL 6550 (1965 triplegetter- withholes) cially the KT88. Firsr, we shall revisit the origin of (he 6550 family. thought was plenty. The transmitting-tube circuits must haveb een seen as luxury projects iorended only for the 2. 6550 serious "audio bug. � Such amps were not ordinaily avail­ able from early hi-fi dealers. In (he halcyon days of hi-fi, getting more than 30 wans was very expensive. it required at least four 6L6Gs at typi­ Power was the need, even 'though most people were cal 300-400v plate vohages, or rransmining tubes at much using relatively efficient speakers and horns were at the higher volrages. Even thou h a pair of 807s would do the g peak of opularity. Bear in mind that these users were job, the plate voltage would have to be morc than 550-­ p nearly all middle-aged men who listened primarily to clas­ this usually required oil capacitors in the power supply, sical music; hi-fis weren't used for rock'n roll until the late plus more expensive transformers that were rated for such 1960s. They must have been desperate for louder crescen­ operation. The price added up, and by the time the cus­ dos, perhaps to drown out the wife's TV shows? tomer has paid for a runer, turntable, speaker, and the mandatory cabinet, there wasn't much left for a transmit­ The RCA 6146 was a landmark tube in some ways. It ting-tube power amp. was rated to take 750 volts on i(5 plate, and a pair was good for 100 wattS. Bur its high cost meant that it never There was unquestionably a srrong desire for such prod­ saw commercial use in hi-fi. The only major audio amp to uCts. ConsnuC[ion articles in Audio E"gilleerillg in the use it was the Aitec 1530, an industrial-looking rack­ 1948-1954 frame often featured large tubes. The Audio mouor PA amplifier. And the only well-known instrument Anthology books, volumes 1 Ihm 3, contain 21 amplifier amp with 6146s \Vas the early Ampeg SVT bass-�uitar construction arricles, of which onc used 211 s, twO used amp, introduced in 1964, well after the time penod we are 807s, one used 845s, and one used the type 6146, which covering. Obviously there was a demand for a tube that was new in 1952. The vast majority of the amp circuits could do more than 50 watts, with low distortion, at a were good for less than 15 watts, which most people cost below that of the 6146. Mullard's EL37 could do it bur was about as ex�nsive as the 6146. A need existed, and it was filled in February 1955. And it wasn't done by a giant like RCA, or GE, or Sylvania. It was done by -lunS-Sol, a medium-size tube manufacturer in Newark, New Jersey that catered to the MIL·SPEC market. The 6550 appeared to be heavily influenced by the 6146, but are clearly intended for audio. This was the power tube that started the amplifier power wars. The 6550 was designed for home audio equipment, and it was designed for compact size and coSt-efficiency. No plate cap meant no plate cap connector, with the added advantage of less risk of electrocution to the user when replacing tubes. A large octal base with a metal ring at cathode potential was another safety feature which also improved electrical stability.