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Bias question - 6L6

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  • Bias question - 6L6

    I have a Twin reverb amplifier that I recreantly installed winged C power tubes. As I don't really have time to tinker as much any more I biased using a bias probe. It seems the power tubes are att 23-25 mA when the bias pot is at max. My plate is at 460 so the power tubes are bias quite cold, with these new tubes installed. Prior to them The amp has been kind of average biased.

    Anyone else having the same 'issue' with these tubes? They sound great as they are now, I can't hear any ugly crossover. Should I tinker with the bias pot set up to be able to bias hotter?
    In this forum everyone is entitled to my opinion.

  • #2
    They sound great as they are now
    If the amp works, stop fixing it.
    Education is what you're left with after you have forgotten what you have learned.

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    • #3
      Originally posted by Enzo View Post
      If the amp works, stop fixing it.
      That's what I've been... doing. However, it still puzzles me. Did I just get lucky or are there something special with these tubes?
      In this forum everyone is entitled to my opinion.

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      • #4
        Take a box of output tubes.
        Doesn't matter who made them or what type they are.
        Hook up a rig to test the idle current draw.
        You will find the readings will be all over the place.
        You simply got a 'cold' set.

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        • #5
          New production tubes are SO varying, hence the "GRADING" that some people sell. Used to be, the tubes were consistant. Now, it's more important than ever to check them in THAT amp to see what they are conducting. Many more amps today are beyond spec as far as range of control grid voltage due to the tolerences of tubes. Mike.

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          • #6
            You'll probably kill them if you bias them much hotter, they can't take an awful lot of current/disspation. 12W idle sounds good to me, if the tubes sound good to you? You struck lucky, give yourself a break & a pat on the back.

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            • #7
              Thanks for a the shared wisdom.

              One thing that puzzles me even more than the low wattage is that these tubes doesn't care about bias at all. They sound quite ok no matter how I bias them in my Tvin Reverb.
              In this forum everyone is entitled to my opinion.

              Comment

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