Test-driving preamp tubes--do I have to bias?

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by cranqued, Dec 17, 2005.

  1. cranqued

    cranqued Gold Supporting Member

    Messages:
    450
    Joined:
    Nov 5, 2003
    Location:
    Over hills, far away
    I'm looking to take out the 12ax7 preamp tubes in a Valvetech VAC and replace them (just for a test drive) with the 12ax7's I have in my Bogner Metropolis. Any risk in doing that without biasing? I only need to do it for a short while, to rule out preamp tubes as the source of a tone issue.

    The Valvetech tubes are Fender and Ei. The Bogner has Chinese tubes.
     
  2. VacuumVoodoo

    VacuumVoodoo Member

    Messages:
    1,549
    Joined:
    Jan 9, 2005
    Location:
    Gothenburg, Sweden
    Tubes in preamps are used in a selfbiasing circuit configuration, you don't need to adjust anything. Just do it.
     
  3. cranqued

    cranqued Gold Supporting Member

    Messages:
    450
    Joined:
    Nov 5, 2003
    Location:
    Over hills, far away
    Thanks, VacuumVoodoo! :BEER
     
  4. tralfax19645

    tralfax19645 Member

    Messages:
    581
    Joined:
    Mar 18, 2004
    Hi,
    I always put in V1, JJ 12AX7 V2, EI 12AX7 V3, JJ 12AT7 V4, EI 12AX7 It definately did not come stock with a fender tube.
    Rob
     
  5. cranqued

    cranqued Gold Supporting Member

    Messages:
    450
    Joined:
    Nov 5, 2003
    Location:
    Over hills, far away
    Hmm, there was a Fender 12AX7 in the last slot when I got the amp. The other JJ made it here.

    By the way, Rob, I'll email you later today about the reverb tank I need to get from you.
     

Share This Page

  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.
    Dismiss Notice