Home Forums GuitarPCB Build Support Sunn T volume (answered)

This topic contains 3 replies, has 3 voices, and was last updated by  Barry 1 month ago.

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  • #6092

    fo0dude
    Participant

    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.

    #6093

    Cybercow
    Moderator

    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.

    #6393

    fo0dude
    Participant

    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.

    #6394

    Barry
    Keymaster

    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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