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Peavey Classic 50/50 to Bassman conversion

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  • Peavey Classic 50/50 to Bassman conversion

    In the thinking stages on this. I have a Peavey Classic 50/50 stereo tube power amp that had multiple PCB arcing issues on channel B, and I have given up on fixing it to original function. Thinking about converting it to something more interesting. Thinking about either a Bassman 50 or Ampeg B15N. Bassman has an advantage of having some cheap pre-made/pre-populated eyelet boards available. I think either amp I would have similar questions on convertibility.

    Most importantly I guess would be PT and OT specs. The 50/50 has 8 EL84s (four per channel) and plate voltage is about 450V. It seems to me like I should be able to run a couple of 6L6 tubes off this, but need to come up with the correct bias voltage from somewhere. There are two 12AX7 and two 12AT7s for the buffering and PI stages, so that seems like there should be enough current for preamp plates. Heater current should be enough considering 8x EL84s and 4x 12A_7 tubes. Is this reasonable?

    For the OT, is a quad of EL84's much different than a pair of 6L6 from an impedance standpoint? I've read 8k per tube for EL84 and 4K for 6L6. Is there a reason I couldn't use a pair of 6L6 with one of the existing OTs?

    Haven't really thought about tube rectification vs. SS. Mostly this came about because I am having a lot of fun playing bass through my Peavey 60/60 with just a tube mic preamp in front of it, and think it would be cool to have a "real" bass tube amp (I know the Bassman is known more for guitar).

    Thanks for any thoughts,

  • #2
    Do Peavey use DC heaters in this circuit for the preamp ?
    Last edited by copperheadroads; 10-02-2018, 11:45 PM.
    "UP here in the Canada we shoot things we don't understand"


    • #3
      Apologies, forgot to include link to the 50/50 schematic (related to the Classic 50 but perhaps not identical). Heater voltage is AC according to schematic.

      Oh, and I would not try to mount the tubes horizontally like the EL84s are, I would put them vertically up through the top cover or something.


      • #4
        The Classic 50/50 doesn't much resemble the Classic 50 at all. The Classic 50/50 doesn't have a preamp, it is just a power amp. The 50/50 also has a driver stage for the power tubes that the Classic 50 lacks.

        Forget tube rectifiers, there is no 5v supply for their heaters, and where would you put them?
        Education is what you're left with after you have forgotten what you have learned.