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SVT-3pro tube question

Discussion in 'Amps and Cabs [BG]' started by slipknot229, Sep 1, 2001.

  1. Attention all ampeg/tube experts. I recently acquired a used Ampeg SVT-3pro from guitar center. It sounds AWSOME except for one minor detail...I think the tubes may be dying on me. I opened 'er up and had a look-see and the tubes looked cheap...no labels (except on the 12AU7...thank God otherwise I wouldn't know where to put in the new one!!!) and I'm not sure but I think Ampeg tubes their amps with groove tubes(?). Basically, I was wondering if anyone with knowlege on this topic can tell me which "slot" the 12AU7 goes into? just in case the person before me retubed it incorrectly. Thanks a lot in advance. I hope what i just typed makes sense....

  2. it really doesnt matter. a 12au7 is the same as a 12ax7 except its got a lower gain circut, i believe its 40%? and then there's a 12at7, which is 20%? i might have the two mixed up. Just mix and match around the 12ax7's, and 12au7's and see what sounds best.
  3. so theoretically, i could just put 5 12AX7's in it? hm....im also assuming that whatever preamp tube i want as long as it fits in the recepticle? idunno....im a tube ignoramous.
  4. as far as i know, you can put any of the fallowing tubes in the tube spots...

    7025 (which is basicly a 12AX7)

    There are many different kinds of pre-amp tube's out there (brand's wise) which sound totally different from eachother, and price wise, they could go from $10-$50 per tube. shop around, see if you can find some good NOS stuff.
  5. thanks a lot for the help guys! i really appreciate it.

  6. Funkster

    Funkster Supporting Member

    Apr 6, 2000
    Wormtown, MA
    My new SVT pro had a weird girggling sound coming from it, I opende it up to find all groove tubes except for the 12au7 that was some cheap tube made in China and it was very weak looking,
    I changed that one tube with a vintage RCA 12Au7
    all the noizez went away and my amp sounded way better with the RCA as a driver tube.
    I bought mine brand new so they do pu GT's in there amps except for the driver tube.

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