Bad phase inverter tube a possible culprit for volume loss?

Discussion in 'Gear & Equipment' started by broj15, Sep 26, 2016.

  1. broj15

    broj15 SS.org Regular

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    So my bassist ended up buying a used Traynor YBA 200-2 after trying out a YBA 250 at guitar center and falling in love with it. He met up with the guy at a halfway point so he didnt get to test it out before buying it. He got it back to our practice space and with the gain AND master both all the way up it just wasn't very loud. After a lot of messing with the eq and trying it through 2 different cabs (ampeg svt 2x12 and my cheap hartke 4x10) it still wasnt loud enough. For reference "not loud enough" means that even when cranked he wasnt audible over me or our drummer. I turned my volume down to half of what I normally play at (4 as opposed to 8 on my 60w 6505 2x12) and he still wasn't audible.

    We decided to take a look at the tubes and the power tubes all APPEAR to be good, however the V3 tube in the preamp (12au7) isn't glowing, but also produces no noise when we did the "pencil test" on it. I'm assuming that since it's not glowing like all the other tubes it's gone bad.

    Now, I think I have a rough idea of what the phase inverter does (sends the signal from the preamp to the power amp ?) which leads me to believe that that could be causing the volume issue, though I could be wrong.

    So, I guess my questions is, Is it possible that a bad phase inverter tube cause the low volume problem, and if so, would playing the amp in it's current state cause any potenial damage? and if that's not the case are 200 tube watts just not enough for a bass amp? I know bass amps are typically rated for higher wattages because bassist need more clean headroom, and because it takes more watts to push the low end frequencies.

    Any help is appreciated.
     
  2. TamanShud

    TamanShud Finished

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    I'm no tube amp expert so I can't confirm or deny anything about your idea with the phase inverter. But, 200 watts in a bass amp should be hella loud! Ampeg SVTs are 300 watts and could kill a horse with the amount of output on tap. I'm pretty sure Orange's tube bass head is in the 200 or 300 watt range too.

    Good luck to your bassist getting it sorted, once it's fixed up it should roar :yesway:
     
  3. maggotspawn

    maggotspawn SS.org Regular

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    Could possibly be the PI tube, my guess is the power tubes though.
     
  4. vick1000

    vick1000 SS.org Regular

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    Tube no glow, tube no good, signal no go through tube. I would replace all the tubes with kown good ones, possibly new ones from a reputable dealer that tests them, and burns them in.
     
  5. tedtan

    tedtan SS.org Regular

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    Could be the PI, though I would think it would kill the sound altogether if it was. Anyway, most issues with tube amps are the tubes, so I would start by replacing the tubes.
     
  6. TedEH

    TedEH Cromulent

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    Are you playing through a cab that's known to be reliable and efficient? Is there an impedance mismatch? 200 tube-watts should be enough, in theory- but my understanding is that your cab has a lot to do with how well you're putting those watts to work. I don't remember the math, but if you've got a mismatch that's cutting your wattage in half or something like that, and the speakers aren't super efficient to begin with, then it's going to be a struggle to keep the volume up. My first bass cab was an 8ohm 4x10 that just couldn't keep up with a drummer no matter how many watts I threw at it. Something like those ampeg fridges, on the other hand make everything loud.
     
  7. broj15

    broj15 SS.org Regular

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    ^^^ It's an 8 ohm head and its going into an 8ohm cab. We tried it with my hartke 4x10 and his ampeg SVT 2x12. Both cabs have suited us fine when we used my Hartke vx3500 (before it had issues with overheating) and his ampeg portaflex 500 (before the fault light came on and it stopped working entirely). He's getting a new 12au7 today and we're gonna swap it out tomorrow night to see if that helps.

    We did find that turning the "scoop" knob completely off did help as this amp is apparently already scooped, but we both feel like it could be louder.
     
  8. broj15

    broj15 SS.org Regular

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    Just a little update. We replaced all the preamp tubes (tung sol in V1 and EHX in V2 and V3). Turns out the old owner put a 12ax7 in the V3 slot when the sticker on the back clearly specified it was supposed to be a 12au7. I know you can swap 12ax7's for 12au7's and vice versa, but I have a feeling that could've been causing the issue. Long story short We played 2 shows with it this weekend going into his Ampeg SVT 2x12 and it sounded great and was plenty loud enough.
     

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