Came across this one and it's an interesting JFET-based OD with active bass and treble controls. It's apparently based on a late-60s Marshall 200 amp. Drew up the schematic for reference.
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I believe the originals run off a 9v supply, but newer ones have a voltage doubler internally to run off 18v. Since I know there are different preferences when it comes to those, so I left it off the board. I realized after I drew all this up I probably should have included trimmers for biasing the JFETs, so you may want to socket the resistors going from voltage to the drain of Q1, Q3, and Q4-6. Though if you're using in-spec J201s (I highly suggest the SMD version and conversion boards) the stock values will probably work fine. YMMV Pots are board mounted and will fit nicely in a 125B.
