EL-84--Sovtek vs. J.J ??

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by brianwenz, Jun 22, 2004.


  1. brianwenz

    brianwenz Guest

    Hello Hello-
    I've got a Crate Vintage Club 30 [class A] sitting here that needs power tubes. It has had Sovteks in it up 'til now and was wondering what differences I can expect after changing to Tesla J.J.'s ???
    Thanks!
    Brian.
     
  2. vladorg

    vladorg Supporting Member

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    Hi Brian,
    I'm in no way affiliated with JJ but I can tell you the difference will be huge it'll definitely thicken your tone. Visit www.eurotubes.com and give Bob a call or e-mail him. He's the man and can definitely recommend what you should do.Still,IMHO JJ's are one of the best (if not teh best) in production tubes and way better than Sovtek's.Give 'em a try and let me know what you think,

    Vlad
     
  3. brianwenz

    brianwenz Guest

    Hello Hello--
    I put a quartet of J.J.'s in a while ago, and after a half-hour burn-in I tapped on each tube to check for any obvious problems..........well, one of 'em went all "4th of July" on me and I started getting that "whooop" racket coming through the speaker, so I turned the amp off. I'm going to replace the bad tube tomorrow and try again! Up until the lightshow started everything seemed o.k....nice even 'glow' on each tube, etc.
    Brian.
     
  4. vladorg

    vladorg Supporting Member

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    Hey Brian,

    that's possible too.I guess you had a faulty tube.I don't know where you bought it from but still call Bob @ eurotubes.com and talk to him he'll definitely help plus don't forget that you might have to rebias your amp after changing the tubes.

    Vlad
     
  5. brianwenz

    brianwenz Guest

    That's why I was wondering if the J.J's could be direct replacements for the Sovteks......the Crate Vintage Club 30 is a class-A amp [like a Vox AC-30] and the Sovteks work perfectly in the circuit.
    Thanks!
    Brian.
     
  6. vladorg

    vladorg Supporting Member

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    Hi Brian,
    as far as I know there is no such thing as direct replacement for tubes on amps with adjustable bias.When you change your power tubes you will always have to adjust the nias more or less no matter what brand of tubes you're swapping with.That said,taht's why I advised you to contact Bob because he knows all about taht stuff and if you are not comfortable with biasing your amp you're gonna have to get it done by a tech or someone who knows how to do it.Let me know how it goes.

    Vlad
     
  7. Mark Robinson

    Mark Robinson Member

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    The amp is cathode biased, which means it's self biasing, but probably fairly hard on tubes, particularly if it's based on the Vox AC-30 design. Class A is a descriptor of a tube's operating conditions over the duration of a waveform, and has been misapplied as a marketing word, to lots of amps that might run in class A once in a while. What you have there is a cathode biased amp.

    I've used both Sovtek and J.J. El-84 in my Guytron which configures them cathode biased. The Sovteks to my ears are a little harder and brighter sounding right away, and deteriorate more slowly than the J.J. tubes. I prefer the J.J. tubes, sonically, smoother, but with detail where you want it. The problem is that the Guytron can beat them into the ground pretty quickly. I've had pretty good luck with some tube vendors supplying tubes selected to draw somewhat lower current, which lengthens the life a bit. Lord Valve has done this for me.

    I've had both brands give up the ghost, loss of vacuum with Sovtek, but with the J. J.s they dwindle until the amp just has no headroom one day, I swap em out, and it's back to normal.

    The Ei El-84 are well thought of by some of the Vox fans. Which ever way you choose to go, use a reputable vendor like KCA or Lord Valve, or Euro, etc. cause for an amp like yours, they should be screened and qualified for microphonics etc. It's worth a couple bucks extra. You might even want to get a few quartets and do some listening, see what you prefer. They are inexpensive relatively speaking, and it's fun to do.
     
  8. brianwenz

    brianwenz Guest

    Hello Hello--
    Yeah, that's what I was getting at about swapping the Sovteks for J.J.'s...it's pretty much a self-biasing circuit. I do all my own tech work and can get various brands of EL-84 tubes.
    The amp has run great with the Sovteks but I wanted to try something different and didn't know how the circuit would react to a different brand. As soon as I get time I'll replace the defective J.J with a different one and see how it goes.
    Thanks so far, Vlad and Mark!
    Brian.
     
  9. alwebber

    alwebber Guest

    I've used both. For me the JJ's sound warmer - the Sovteks can sound a bit harsh, but the JJs don't seem to last as long.

    I do prefer the tone of the JJs.

    Al
     
  10. brianwenz

    brianwenz Guest

    Hello Hello -
    Thanks, Al!
    Brian.
     

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