Home Forums GuitarPCB Build Support PURP trimmer questions

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    Two quick questions about the trimmers on the PURP board:

    1. I want to replace TR2 with a pot. The trimmer is a 10k so would the pot be a B10k or an A10k?
    2. The build doc says to set the bias trimmer (TR1) to 6.8-7.8v on Q1 but in order to adjust TR2 properly TR1 has to be turned all the way up.  Does that mean TR1 needs to be set first or does it mean TR1 should be turned clockwise as far as if will go?
    3. Since I want TR2 to be external would it work okay to set TR1 to the appropriate voltage and then set TR2 by ear?

    Thanks much!


    I’d bias the circuit first via TR1 setting Q1 C voltage to between 6.8 and 7.8v and use a B10K for TR2

    Germanium transistors will vary so I personally bias by ear to where I like it



    Excellent.  Thanks Billy.

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