Tube for GT preamp

Discussion in 'Amps and Cabs [BG]' started by poundround, Jul 23, 2005.

  1. poundround


    Mar 8, 2005
    Lynchburg VA
    I just bought a GT preamp off e bay for $200. The guy said he never has replaced the tube and didint know what it is. I want to replace but I got to find out what it is. If anyone could tell me that be great. :bassist:
  2. Steve


    Aug 10, 2001
    The GT preamp's are pretty much an SWR product....I'll bet you a hundred bucks the preamp tube is a 12ax7. The SWR stuff is known to be tube sensitive in can actually hear the difference between the tubes you use. I have two SWR products and they ARE tube sensitive.

    I stepped up to the plate....(NPI)....and spent the money on nice Telefunken tubes.
    I haven't regretted it.
  3. Reefer

    Reefer Guest

    Mar 9, 2003
    The original tube is a Groove Tube 12ax7. The GT tubes from the era that your preamp was built are actually Chinese tubes that GT just put their names on. These same tubes can be found on eBay real cheap without the names on them. I tried quite a few different tubes in my SWR stuff and yes they will change the way the amp sounds, but I always went back to the stock tube.
  4. tornadobass

    tornadobass Supporting Member

    Nov 20, 2000
    Iowa City, Iowa
    Endorsing Artist: Black Diamond & SuperSensitive strings
    My favorite tube in the SWR SM-400 is a JJ/Tesla ECC83 version of the 12AX7. Both clear and full sounding...good punch!

    You'll get lots of favorites suggested. Good thing about this tube is you don't have to hunt it down...they're easy to find.
  5. What is stated above is absolutely correct. I tried several tubes and each one was noticably different.
    I put a NOS RCA Blackplate 12AX7 in my SWR and made a vast difference.
    Telefunken sound very interesting.
  6. poundround


    Mar 8, 2005
    Lynchburg VA
    Well im glad to find its tube sensitive. I got ideas, I think. Thanks guys.