They stopped making this pedal in 1997. I bought one these back in 1994. I have a Randall RG200 G3 and have added this pedal in the effects loop. It's makes this amp sound like hell's fire with the adjustable Mid and High frequency’s on this pedal. It kinds of adds the same feature Dimebag Darrell had on his Randall Warhead amp with the adjustable Mid frequency. Don't want to see this Gem of a pedal to Disappear.
Pres, High, Low and Mid pots are all connected to a 47uF cap going to ground.
From which lug are they connected?
They should be W taper center-tapped pots and I'm not sure how to build (if at all possible) a clone with regular pots.
I did some home work. That 47uf cap is basically a loudness control. That 47uf cap give the circuit the extra 3db. That's why all the other parametric EQ or Graphic equalizer only do -15 to +15. In the Boss PQ-4 circuit the add the loudness control which is one 47uf cap and center tap potentiometers. A pretty cool and cheap way to get an extra -3 to +3 in stead of being -15 to +15 you get the -18 to +18.