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Thread: Tremolo effect pedal build

  1. #1
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    Tremolo effect pedal build

    Hi

    I want to build a tremolo pedal for my own use
    vibracaster-12au7-v2.jpg
    I have built it and it works, But not as well as i hoped

    The main problem is the depth. When i turn it fully off it increases the volume and only starts to work at about 12 o'clock
    The speed is better but i would like it to be more controllable, again it dont really work much until 12 o'clock
    I have made it exactly to the circuit
    I was going to try audio taper pots, but before i rip it out any idea's

    BBB

  2. #2
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    If it only starts to work at 12 o'clock with linear pots then with log it will be worse. With linear, 1/2 rotation is 50% of the resistance, with (most commercial) log pots this equates to 10% of the resistance.

    Try wiring up a log pot backwards to simulate a C taper pot. If that works OK either leave it like with reverse-operation controls, or order some C taper pots.

    The volume shift is a characteristic of the design. Amongst other things the NFB changes due to the varying cathode resistance - more NFB as the depth increases, so lower effective gain.

  3. #3
    Supporting Member Chuck H's Avatar
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    I can't look at the circuit and determine how it sounds. Is this a known good circuit. "Known good" being relative. As in did some guy say he made this and it's good or is it a popular design that is known? Many tremolo circuits use reverse audio pots. It's possible the behavior is "normal" with linear pots. The increase in volume with the trem off is a problem to be sure though. If you have a scope you can monitor signal swing to see if the trem is biased a little cold relative to when it's off. Properly, the trem will be a bit hot on peaks and, obviously very cold on the low volume or off modulation.
    "The man is an incompetent waste of human flesh. He should donate his organs now to someone who might actually make good use of them." The Dude re: maybe I shouldn't say, but his name rhymes with Trump

    "...less ear-friendly but handy for jazz." Leo_Gnardo

  4. #4
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    See post #222 here to reconfigure the depth control and add a cathode bypass cap (to remove the variable NFB, though the post refers to this as an anti-pop cap);

    Vibracaster - or "How to turn your Valvecaster into a Tremolo"

  5. #5
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    Thank you. I will look into the changes

    BBB

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