Cathodyne PI: Using other half

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by Nolatone Ampworks, Mar 27, 2008.

  1. Nolatone Ampworks

    Nolatone Ampworks Silver Supporting Member

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    Based on the cathodyne PI using only 1 triode of a 12ax7, has anyone ever tried using the other half of the 12AX7 for anything else?

    In my 5E3 "test lab" I'm thinking of trying to use that other half as a cathode follower to drive a tweed Pro style tone stack, then into the Cathodyne.

    On a tweed Pro, they have an extra preamp tube to develop the cathode follower, but I'd like to keep both sides of V1 for pre volume control gain.

    Thanks in advance,

    Paul
     
  2. Blue Strat

    Blue Strat Member

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    No reason, in theory, why it shouldn't work.

    Practically, it's never a good idea to have the signal path going back and forth (right to left, then doubling back to add a gain stage) due to possible unintended cross coupling and positive feedback which leads to perpetual squealing. Congrats in advance if you can make this work.
     
  3. Nolatone Ampworks

    Nolatone Ampworks Silver Supporting Member

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    Right now I'm not looking to do back and forth (if I'm understanding you correctly):

    input->V1->Volume->V2a(as cathode follower)->tone stack->PI->Output

    I'll agree on the back and forth thing though, I had that very problem with some experimentation last week!
     
  4. KLB

    KLB Member

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    Steve Carr uses the other half of the 12AX7 cathodyne PI in the Vincent for the Drive control. As it is turned up, it gooses the dry side of the parallel path with the reverb. The signal gets fatter, with more harmonics and easier breakup. The reverb sounds better with low settings of Drive.

    Great amp!
     
  5. mark norwine

    mark norwine Member

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    How about a trem?

    (just ignore me.....I love a good bias trem...)
     

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