ampeg J-12B thoughts

Discussion in 'Shock Brother's DIY Amps' started by motor_city_tele, Dec 30, 2017.

  1. motor_city_tele

    motor_city_tele Tele-Afflicted

    Apr 25, 2005
    motor city
    Am I addicted or what. You guys are all enablers.

    I was browsing through the shockzone and responded to a question about which amp to build, blah blah blah. I remembered that the valco site had a bunch of schematics and stuff. Well after posting the link I returned to it and started clicking on them myself.

    Then it showed up.

    The perfect amp to build inside the 5C3 chassis I screwed up a few years ago. An Ampeg J-12B. I don't think I'll need to purchase very many components either.

    PT - I got a few that will work
    tubes - 6SL7, 6V6, 5Y3 - got all those
    octal sockets - got a bunch
    big caps - 20uf 450volt - i think i have some.
    speaker - 12 inch - in shed, i think
    pots - i might have some
    pot with a switch - I'll need one of these
    resisters - got a bag of these somewhere.

    schematic - at the bottom

    I do have a question about the bypass cap on V1 pin 3
    it says 100uf - thats it, no voltage.

    what might be the correct voltage on this cap?

    Oh one more thing. I've read that the tremelo misbehaves in many of these amps.
    any proactive ideas?

    Last edited: Dec 30, 2017
  2. corliss1

    corliss1 Friend of Leo's Platinum Supporter

    Sep 13, 2008
    Lansing, MI
    All the fender bypass caps are in the 25-50v range. 100uf/100V is a common value to find if you need one, and 100V would be more than plenty in that spot.

    Also...I never trust Joe Piazza drawings. I've found so many issues in them over the years.
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