Moving from EL34 to 6L6 in a Plexi

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by timc, May 28, 2015.

  1. timc

    timc Silver Supporting Member

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    I have a Cornell Plexi, and curious as to the change in the overall tone of the amp if I install and bias up 6L6's? Denis sent me the bias spec's for 6L6's, but I am just curious as if the 6L6's will remove some of the mids?

    I am getting a certain freq, seems to be in the upper mids, that rings in my ears that I cannot remove with eq or various speakers that I have onhand and tried. I do have a good set of NOS 6L6's that I'd like to try though...

    Oddly, I do not get this with my Friedman DS that is based on the Plexi and runs 5881's....

    tim
     
  2. Steppin' Wolfe

    Steppin' Wolfe Member

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    I am interested in hearing what you hear with such a change. The basics of the sound are established by the circuit, imho; but the tube choice and the biasing thereof play a role, for sure.
     
  3. donnyjaguar

    donnyjaguar Member

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    I think you'll find the output transformer impedance is better suited to 6L6GC tubes. I've never run an EL34 amp with 6L6 tubes (because IMO EL34 sound great), but you'll be presenting a much lower than ideal impedance to them. It'll sound different alright, and don't expect full-power, and I would guess the 6L6 tubes will be rather strained in this application with reduced gain and lower damping factor. But of course, I'm not famliar with this version of the Plexi so perhaps the output transformer has a higher primary impedance.....
     
  4. TimmyP

    TimmyP Member

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    Have you experimented with different preamp tubes?
     

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