Is there a way to get more gain out of this circuit.
This is the schematic I found:
(http://4.bp.blogspot.com/-pgDMzXAv3Pw/TxxcF2JgeNI/AAAAAAAAAqg/zYABLMqgeXA/s1600/Crowther_Hotcake-2003.gif)
I think that the gain resistor should be R7, R6 and the potentiometer Drive itself. It's a bit odd (for me) the root R8, C4 and R9, it could be involved even it.
Did you build it, yet? Or do you have an original pedal?
The gain stage is a non-inverting op amp amplifier. So, the basic voltage gain equation is:
Av=1+(Rf/R1)
Av = voltage gain
Rf = feedback resistor
R1 = resistance to ground
The presence control and other frequency shaping elements are in the feedback loop, so it's a little complicated. Changing values here will alter the tonal character of the circuit. R1 is the series resistor and the drive pot—I wouldn't change these: increasing the series resistor would lower the gain of the circuit. You might be able to increase R7 (R4 in the fritter build) to get more gain, but I'm not sure what changes would be made to the overall frequency response.
I suspect that this circuit cannot be simply changed from overdrive to distortion. The lack of clipping diodes suggests that this would move to saturated op amp fuzz instead. This is such a low part circuit that I'd suggest breadboarding it to see what works. Hopefully someone with better insight can chime in, though.
Stick a pair of clipping LEDs across pins 1+3 of the gain pot and see what happens. Turns the Dist+ into a crazy good distortion pedal.
Change R6 to 100R and C3 to 22uf.