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Bias vary trem in 5F6A type amp?

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  • Bias vary trem in 5F6A type amp?

    My next build is going to be a 5F6A. (I have the trannies and the choke already.) I was wondering about putting in a bias-vary trem (because I really liked that in the 5G9 I built). So I add another 12AX7 (no problem for the PT). I understand (from my previous build when I tried subbing higher gain tubes in V1) that oscillator circuits can respond unexpectedly with 'chirps' and 'peeps' if the gain is different. Does anyone have an opinion on how well a 5G9 trem circuit would run in a 5F6A? (No doubt the values in the LFO circuit can be adjusted to compensate? - and I know I will have to get the plate voltage in the 12AX7 to a reasonable level)

    Cheers
    Building a better world (one tube amp at a time)

    "I have never had to invoke a formula to fight oscillation in a guitar amp."- Enzo

  • #2
    Hi TW,

    Why not just do as in a 6G16 (BrF '63 Vibroverb)?

    MPM

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    • #3
      Done that, works nice

      Hi there!

      I did that in my SF twin reverb because the opto coupler was dead.
      It's totally different sounding IMHO.

      When I build my Pro 5E5-A clone I added an extra 7 pin connector to supply the bias, B+, filament heaters and preamp in/out. This way I can hook up an external trem oscillator to bump the power tubes.

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      • #4
        Otherwise tweed bassman

        Originally posted by martin manning View Post
        Hi TW,

        Why not just do as in a 6G16 (BrF '63 Vibroverb)?

        MPM
        Good suggestion thanks Martin. (The PT I have is tweed bassman spec (325-0-325 200mA), otherwise I could build a 6G16, but no reason why the Trem circuit from the 6G16 wouldn't be good in the (otherwise) tweed bassman I guess).
        Building a better world (one tube amp at a time)

        "I have never had to invoke a formula to fight oscillation in a guitar amp."- Enzo

        Comment


        • #5
          Hi TW
          I don't see any problems with the bias-vary trem in the 5F6A (just don't bias it too hot).
          The 6G16 is one of my favorite amps of all time but if you go for the classic Bassman sound you should stick with the 5F6A. As you know they're totally different sounding.
          I think Martin meant the same, like just to use the trem in the WAY of a 6G16.

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