SVP Preamp tubes

Discussion in 'Amps and Cabs [BG]' started by Davidoc, Apr 19, 2003.

  1. Hmm, i want to replace the tubes in my Ampeg SVP-pro. I hope it will remove noise and/or sound better.

    What tubes should I look into? What brand/model?

    Also, is it important to have a 12U7 in the 4th tube slot? (Right now I have all ax7s due to do being replaced by a tech-removed most buzz, but i wanna kill the buzz totally)

  2. It should be okay. If your preamp is buzzing, it could be a few things. Poor grounding perhaps. erm poor contact of the pins in their sockets not biased properly etc. Try to get a 12AU7 as they would have slightly different characteristics than a AX7 but they're fairly similar.


  3. I had an SVP-PRO up until last week. If you're getting some hum the first thing to check is tubes. If you have a known good 12AX7, take the preamp out of the rack, connect it to the power amp with a long instrument cord and swap the tubes out one at a time until you find the bad one.

    The other fairly common problem with early SVPs is bad solder joints on one end of the circuit board - but the preamp has a five-year transferable warranty. Retube first, though.

    You can use a 12AX7 in slot #4 as long as you don't crank the drive control - electrically it's probably okay but a 12AU7 has less gain than a 12AX7.

    Lord Valve hooked me up with some NOS Beijing 12AX7s and we replaced the 12AU7 with a JAN 5751, I believe. I think I spent about ten bucks apiece for the tubes and it made a world of difference. You might want to ask him - I was very happy with the tubes he recommended.
  4. boogiebass


    Aug 16, 2000
    Go figure. I did the same mod with Lord Valve and it made no difference at all with my SVP! Didn't sound any worse, tho, so I left 'em in.
  5. rockbassist1087

    rockbassist1087 Guest

    Nov 29, 2002
    Long Island, NY

    Yes they do.:)