Home Forums GuitarPCB Build Support Sunn T volume (answered)

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    Hi there, I’m making my first ever pedal and (of course) ran into some issues.

    I’m making a sunn model T, I bought a kit of off das musikding and I had some problem biasing, I couldn’t get it below a reading of 9V. After closely looking at the schematics I think I’ve found the problem. I think my trims are to low a value, I think they’re a 2.5K instead of the 25K.

    When I plug it in to see how it sounds i’ve found it to be a very low volume in the gain staging, it would distort at all, I needed to put a clean boost of about 18db in front of it to get it to break up a bit. Could this be related to the biasing issue?

    I’m glad I’m doing this. I know it looks messy, I’ve learned a lot already i feel and I would doe it differently next time.


    It’s clear that at least one of the biasing trimpots is 2K5 Ω, but all three bias trimpots need to be at least 20K Ω. (25K Ω trimpots will do nicely.) With proper trimpots, you won’t need a boost in front to get it to break up. The incorrect bias pots will a significant bearing on the operation of the circuit. I built one last fall, and when using both channels and all pots dimed, it breaks up nicely. If you were to replace those 2K5 Ω trimpots out for 20K Ω or 25K Ω, you should be back on track.


    I changed the trimpots and now it’s working fine.

    The only thing I noticed now is that the bass knob has hardly any effect. Non the less it sounds great. I’m making a second one for my friend now.


    Glad to here.

    Be sure that none of the unprotected potis backs will have a chance to short out against the board or solder joints. Anything non-conductive will do nicely even some 3M double sided tape.

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