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  • 2 bias pots

    I am stuck, trying to figure out if it is possible to have separate bias pots for an amp (let us say a Fender Princeton) that uses bias vary Trem.
    When I look at the schematic, I do not understand how to send one bias pot to the gird of each power tube....but also run it through the Trem circuit. Maybe it is simple.?.....but I do not see how to get around the Tremolo pot, with 2 bias pots. How do I do that.?
    Thank You
    http://www.webphix.com/schematic%20h...z34_aa1164.pdf
    Last edited by trem; 09-21-2011, 11:05 PM.
    https://www.youtube.com/watch?v=7zquNjKjsfw
    https://www.youtube.com/watch?v=XMl-ddFbSF0
    https://www.youtube.com/watch?v=KiE-DBtWC5I
    https://www.youtube.com/watch?v=472E...0OYTnWIkoj8Sna

  • #2
    Try this.
    It is a dual pot circuit from a Marshall DSL.
    Attached Files

    Comment


    • #3
      And for the other half of it, check this out: http://music-electronics-forum.com/t5415/
      -Mike

      Comment


      • #4
        Thanks for the replies.....amd maybe I missed your points....but I do not see how to get around the Tremolo.
        I understand (or think I do) how to split the bias circuit to run 2 tubes separately.....but I do not see how to get past the the Trem with separate bias. The Trem varies the bias.....so how do you get 2 pots to work with the Trem circuit.?
        Thank You
        https://www.youtube.com/watch?v=7zquNjKjsfw
        https://www.youtube.com/watch?v=XMl-ddFbSF0
        https://www.youtube.com/watch?v=KiE-DBtWC5I
        https://www.youtube.com/watch?v=472E...0OYTnWIkoj8Sna

        Comment


        • #5
          Looking at the trem tube, there's a 0.1u coupling cap and the intensity control. Everything to the right of the 250KL intensity control is the bias circuit. What the intensity control does is balance between the steady DC bias and the output of the trem tube. If you make a circuit with two bias circuits in parallel, intensity control and all, and connect the two intensity controls to the 0.1u cap, you have dual bias trem. You can either gang or have individual intensity controls, that's up to you.
          -Mike

          Comment


          • #6
            Originally posted by defaced View Post
            Looking at the trem tube, there's a 0.1u coupling cap and the intensity control. Everything to the right of the 250KL intensity control is the bias circuit. What the intensity control does is balance between the steady DC bias and the output of the trem tube. If you make a circuit with two bias circuits in parallel, intensity control and all, and connect the two intensity controls to the 0.1u cap, you have dual bias trem. You can either gang or have individual intensity controls, that's up to you.
            10-4......
            Thank You Very Much
            https://www.youtube.com/watch?v=7zquNjKjsfw
            https://www.youtube.com/watch?v=XMl-ddFbSF0
            https://www.youtube.com/watch?v=KiE-DBtWC5I
            https://www.youtube.com/watch?v=472E...0OYTnWIkoj8Sna

            Comment


            • #7
              Dual Bias with Tremolo split

              I have the same problem with my YGM-3 circuit....I decided to ad the split bias controls, great, but then I ran into the same problem with the tremolo running off the intensity pot. I see how they are now supposed to be split, and run via the .1uF coupling cap, so I will try this per the prior answer. My question is if anyone has a drawing of this for referral...if not I will finish my mod and put up a drawing I have that I have made of the YGM-3 circuit with autocad, using this new bias split showing that and the dual intensity pot for the tremolo.

              Comment


              • #8
                Bias Pots with Dual Tremolo Intensity Pots

                Here is a diagram I have drawn up that shows my interpretation of this Bias/Tremolo mod for amps that need to add an individual bias pot, but has a bias tremolo circuit.
                Let me know if this looks like I have shown this correctly.Bias Pots.pdf

                Comment

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