Dumble BBC-1 Schematic+Layout

[UltraHookedOnPhonix]

After spending a couple of hours looking at two poor-quality gut shots, I was determined to find out what the Dumble BBC-1 really is and I’ve concluded that it’s basically the FET input of an ODS in a non-bypassable stompbox format (big surprise eh?)

Now I need your help! The circuitry from the input of the effect to the Gate of the JFET is pretty murky in the pictures and I’ve listed a couple of options in the schematic below. What do you guys see? The “Depth” control would to me either suggest a variable impedance circuit, variable input gain or a variable high pass filter. I can’t really make it out…

Also, parts with a (?) after them are components with unknown values. However, since the values I’ve figured out correspond with that of a standard FET input on an ODS, I think it’s safe to assume that there are no big surprises elsewhere except for the input circuit.

I’ve found that the BBC-1 is really close to the Barcus-Berry Hot-Dot Box both layout wise and circuit-topology wise. Wonder which came first?