Peavey Delta Blues - Fixed Bias question

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by guitarwrench, Feb 14, 2008.


  1. guitarwrench

    guitarwrench Silver Supporting Member

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    Minneapolis, MN
    I got a matched quad for the power tubes. Installed them easily enough but do I still need to take this in to a tech to have them do any bias adjustment? Thank you - Dave
     
  2. LowellH

    LowellH Supporting Member

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    If it sounds good and the tubes aren't red-plating, I wouldn't worry about a bias adjustment.
     
  3. rockon1

    rockon1 Member

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    +1 Its fixed bias without an adjustment pot. Only way to adjust the bias is to add a pot or change the resistor/s. Ive changed the tubes in my Peaveys for many years withour biasing and without incident. Bob
     
  4. GearHeadFred

    GearHeadFred Member

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    There are three possibilities..

    #1: You run under-biased: Will shorten the life of the tubes.. If severe, might do damage to other components in the amp

    #2: You lucked out.. The tubes are similar to the previous tubes and biased correctly

    #3: You run over-biased: No risk to components, but the amp may sound unresponsive, or experience cross-over distortion if extreme.
     
  5. guitarwrench

    guitarwrench Silver Supporting Member

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    Location:
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    Thanks. I checked with the place I purchased them and they knew about the fixed biased thing on the PDB and had them handpicked to run in the range per mfg specs. They glow nice and sound just right so I'm going to just leave em be.
     

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