GT Hardness rating and biasing

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by roushc, Dec 30, 2004.

  1. roushc

    roushc Guest

    Does one need to bias if replacing GT tubes of the same hardness?

    Example: KT66-HP #4 Duet in Dr. Route 66
  2. Blue Strat

    Blue Strat Member

    Aug 2, 2002
    Sterling, VA (not far from Washington DC)
    Not if the amp has previously been biased for tubes of the same hardness rating.

    Note that each GT hardness rating has a fairly wide span so rechecking bias is always a good idea.
  3. JDJ

    JDJ Member

    Jan 5, 2002
    What's a hardness rating? Where do you find it on the tube? Thanks.
  4. Kiwi

    Kiwi Silver Supporting Member

    Mar 1, 2002
    In a white room
    Layman's answer:

    GT tests its tubes and assigns a "hardness rating," so buyers can estimate the response or breakup point.

    Their scale is 1 to 10, with rating 1 being very "soft" and quick to break up, and 10 being very "hard", with max clean headroom and late to distort.

    It's written on the tube itself, either a sticker on the base or printed on the tube glass. The end cap of a GT tube package should also have it labeled.

    Guitar store employees usually do not know this rating system and will hand you the first package they can grab. If possible, ask to see what other GT hardness ratings they may have for that type of tube.


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