Update 2 210514
Both schematic and layout is now corrected. A big thank you to Vince who traced the later 125b version which revealed how the active Mid control really works.
Update 1 210514
Caution! There was a mistake in the trace. The Mid control have a different setup than the schematic and layout below indicates. Do not proceed if you want a Mid control that is 100% identical to the stock ODB. I will update the the schematic and layout as soon as I can. Lesson learned, hesistant to trace from gutshots from now on...
Intended for bass but works really good for guitar as well. Based on OCD but tuned for more low end, headroom and gain. Treble and Bass controls is a passive James tonestack and Mid control is an active Bridged-T feedback control. Cut switch is Shelving filter for the first gain stage and Clip switch selects between assymetric MOSFET/Silicon, LED and none clipping. Traced by AlexS and fuzzhead and the layout is verified.
Two things, though. We couldn't figure out the value of the Treble cap in the James tonestack but values between 330pF and 1nF sounds good.
Also, the LTC1144 charge pump is only needed if if you want to run it on 18v to get a 36v swing within the circuit. They are pretty expensive and not that common. MAX1044 and ICL7660S can be used as well but the cut between pin 1 and 8 of IC2 must be omitted. Those charge pumps can only handle a maximum input voltage at 10v and 12v respectively so a 9v power supply/battery is higly recommended...
