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permanently biased amps

Discussion in 'Amps and Cabs [BG]' started by MCR, Apr 24, 2004.

  1. can i use any tube of the same type on a permanently biased amp or do i need to use the manufactures tubes??
  2. By your previous question and this one, I take it you've been reading Mesa's sales literature. Let me save you some trouble: most of it is pure 100% BS, ESPECIALLY the part about "permanent bias." BTW, my issues with their marketing strategy don't mean that Mesa makes crap amps, just that they lie to sell them. Here's why.
  3. Trevorus


    Oct 18, 2002
    Urbana, IL
    It is usually ok if you use the same TYPE of tube, but maybe a differnt brand. You need to look at the tubes after they are well warmed up. If the plates glow excessively, then you need to have it adjusted.

    Permanent bias is not really permanenet. It may be set by a resistor soldered to a board, but it CAN be changed. Some people will also get a potentiometer, and replace the bias resistor so that it will be adjustable. It's a very good mod to have. I hope that helps you.
  4. thanks for clearing that up...i didnt believe the permanent thing
  5. mwbonsall

    mwbonsall Supporting Member

    Aug 2, 2000
    Casa Grande, Arizona
    'Fixed Bias' is a more accurate term, but it can be altered.

  6. And the irony is it is ONLY a fixed bias amp that CAN have its bias adjusted. Cathode biased amps "bias" themselves. A lot of manufacturers also confuse the public by calling cathode biased amps, "Class A" when in fact, most aren't.