Biasing your own amp

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by Obi-Jon, Oct 12, 2005.

  1. Obi-Jon

    Obi-Jon Guest

    I've been reading how-to's on the subject and it doesn't seem all that hard. I'm thinking of picking up a multimeter from radioshack and trying it myself. I have a TOL 100 head that currently uses Ruby Tubes EL34BSTR or something like that. I have a quad of Electro-Harmonix EL34s I want to use instead. Any suggestions, tips, advice would be much appreciated!
  2. UfoPilot

    UfoPilot Member

    Sep 9, 2005
    Be careful touching the wrong thing can be deadly. I use a Weber bias rite so thatt I don't have to poke around inside of my amp while it's on.
  3. stratopastor

    stratopastor Member

    Apr 27, 2005
    NorthEast England
    What you both said. It truly isn't difficult, AND you need a healthy repsect for lethal voltages.
  4. Erik

    Erik Member

    Oct 14, 2003
    Late, great, state of NY
    If you have a multimeter...get a Weber Bias Rite with the "VI" option. That will give you plate voltage and cathode current...all you need to get close enough to the correct bias. I believe you would want to get the Bias Rite "BR+AH" adapter. That is the bias rite without a don't need that because you can buy one from any electronics store.

    It easy...if I can do it, a caveman could do it. ;)

    BTW, the Ruby EL34BSTR's are pretty sweet tubes IMO.
  5. Blue Strat

    Blue Strat Member

    Aug 2, 2002
    Sterling, VA (not far from Washington DC)
    A Bias Rite or similar bias probe is highly recommended. Using one of these virtually eliminates any possibility of electrocution, bad shock, or blowing up your multimeter (or fuse).
  6. rooster

    rooster Member

    Mar 9, 2005
    I have, in the past, re-tubed and biased a TOL100. The annoying thing about this amp was that you had to pull the entire back panel circuit board out of the amp to get to the trimpot to adjust it. If yours is built the same way, this is the biggest danger to you and to the amp circuitry. If the trimpot is easy to get to and you have a socket-type bias probe, you should be OK if you know your way around high voltage electricity. If you are a novice, this is not the amp to learn on. Spend $25-35 on that $1000 amp, and take it to a tech.


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