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6550s or KT88s for 71 SVT

Discussion in 'Amps and Cabs [BG]' started by ROCKBOBMEL_old, Dec 15, 2001.

  1. I have 6550C Svetlana tubes in my vintage SVT. I am thinking about using KT88s (JJ Tesla) when I retube.
    Anyone have experience with these?
    How about KT90s or KT100s?
    I heard that KT88s sounded more solid than 6550s.
  2. Rickenbackerman


    Apr 17, 2001
    Laurel MD
    I don't have an answer for ya... just bringing this one up top cuz I'm curious too.
    Where's Psycho Bass Guy when you need him? :)
    I know he runs EI KT-90's in his (with upped filter capacity) and claims he gets 600 watts!
    I've got a buddy with an SVT-classic with (sovtek i think?) KT-88's and am NOT impressed by the sound. That may because it's an SLM amp, though. KT-88's in a REAL SVT might be another story...
  3. Tapp


    Aug 29, 2001
    USA, Mississippi
    IMHO, KT90's are the best sounding and longest lasting "6550" variant I've used. I do like Svetlana 6550's and for the money they rock! I currently use KT90's in my Sunn Model T; they seem to really shine in ultralinear OT designs. They sound just as good as the NOS GE 6550's I replaced.

    I have no experience with KT88's.

  4. VicDamone


    Jun 25, 2000
    From a 03-16-2000 post by Psycho Bass Guy.

    "Sovtek 6550 and KT88 as well as Svetlana 6550C's and KT88's. AVOID Chinese 6550's like the plague."

    Psycho, if your lurking out there I hope you realize your knowledge of the SVT was an asset to the many who miss your not being here. Thanks.
  5. Yes Vic, you are right. Psycho was a very valuable asset to TB.

    As I understand, he has bowed out of TB because of a few other EEs on this board.
    A great loss.
    I miss him much here. He has helped me personally with some things, also.

    I don't know what happens up there in Techdom. It's over my head. There is a lot to discuss in tube world, and I thought there was enough room for everyone.

    Are KT90s more powerful than 6550s or KT88s?
  6. coyoteboy

    coyoteboy easy there, Ned Supporting Member

    Mar 29, 2000
    Sactomato, CA
    I'm itchin' to tryout the JJ/Tesla KT88's in my DB728. I have a few broken posts in my stock Svet 6550, which is a good enough excuse as any to try something different. I think the JJ 12AX7 and 12AU7's sound pretty good.

    for good prices on JJ tubes see www.eurotubes.com

    p.s. you can get 'em in blue and red glass too!
  7. What do you think? Red or Blue?
    They rant and rave about them.
    I have Svets in the SVT now, but they have a lot of life left.
    The Svetlana 6550s are taken pretty seriously by a lot of companies.

    JJ says that the KT88s will bring new life to the old SVT.
    That is hard to imagine.

    Did you talk to Ag about the KT88s?
  8. Thanks for the feedback. It would be way cool to have the KT90 mod, Maybe we can talk more detail later? My tech is a great guy with lots of knowledge.

    He could probably do it, however, the amp has been to him three times already, and now it is making a loud pop when I flip the standby on, AND on some loud notes, (mostly a fretted A),it makes a loud uncontrolled ghost note on top of the root. So it is going back to him after XMas.

    If it is a cae of power tubes, I don't know if he has some that may have equal wear and will match (So I don't have to replace them all), or I may have to retube. (Hence the KT88 question).

    I am a little skiddish on investing a lot yet because I am not confident all the bugs are out.

    My tech is a very busy guy, and he charges just a token fee ($40. for a cap job). He likes working on SVTs a lot, but I get the feeling he does not want to (or doesn't have time for) getting involved more than he has to.

    He says "it's OK, no problem", but I feel I am bugging him too much.

    I really appreciate his help, but this SVT is having one porblem after another.
  9. boogiebass


    Aug 16, 2000
    Always a pleasure to read your knowledgable posts, PBG. This joint could definitely use more of what you have to offer.
  10. This is what he wrote on the work sheet (original repair -No Sound from amp)
    "Diagnosis: the 8kohm 2 watt resistor used to drop the voltage to the preamp section opened up. Some main power supply caps were previously replaced, but were mounted with hot melt glue.
    Work Done:1) replace open resistor & bad cap in preamp. 2) remove all power supply caps from chassis & replace old ones, remount newer glued in ones. 3)replace all coupling caps in amp section.4) clean all controls, switches, tube sockets. 5) Repace 12BH7 driver tubes & 12DW7."

    Parts 2 LCR 200uF/500V caps $30., 1 LCR 100uF/100F/450V cap $20., 6 sprague .047uF/600V caps $7.50, 3 mounting clamps for LCR $6., 1 8kohm/ 5watt resistor $2.50, 2 12BH7 $24.00, 1 12DW7 $14., (Total $104. + $40. labor) =$144.
  11. Thanks, I will do as advised.

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