Modulation Section Schematic Help

[Bio77]

This is the modulation section from Fairfield Circuitry Shallow Water.  The circuit produces a subtle effect, so, I'd like to increase the amplitude of the modulation signal and give it more range.  I'm in a little over my head here, so I was hoping someone could take a look and see if I'm understanding things correctly. 

The Randomizer is an Attiny chip producing a random square signal.  I'm interpreting the next steps as a unity gain buffer followed by an integrator.  I'm confused about the set-up of the slew control and whether or not changing any of the values of the integrating op-amp will affect the gain.   What I'm thinking about at the moment is bending out leg 2 of the MCP602 and connecting it to R64 via a resistor to create an inverting amplifier from the buffer. 

I'd love to hear what some more skilled people think. 

[thomasha]

What about jumping r38?
Depth only goes to 90% with it in place.

The second OpAmp max. gain (above the 100n bypass) should be
-R_feedback/R_input=(220k+1M||470k)/220k=-2.45.
If you remove the 470k resistor it goes up to 5.45.

[Bio77]

Thanks Thomas! 

I've didn't find any examples of integrators that were also amplifiers.  Still learning this stuff. 

I'm looking for ~2X amplification, so, the second suggestion is going to be better for me.  I tried to breadboard this and mess with switching values, but I couldn't get it working.  I'm going to give it another shot.

[Zerro]

Maybe play around R41-R42 ratio, or put here trimmer 15k instead of them and tune proper threshold? If basic gain here is big enough (2,45), maybe this tuning can help a little.

[Bio77]

So, I made some progress    Thanks a lot for the input, much appreciated.

I breadboarded the circuit from the first half of the slew pot through to leg 3 of the depth pot.  The input was a 20Hz square wave.  Lowering the value of R39 to 100k had a small effect, it increased the signal from 700mV to 750-800mV.  Changing the ratio of R41,R42 to 9.1:9.1 and 6.8:9.1 (vs 9.1:6. both had a big effect but dramatically changed the behavior of the slew pot making it unusable (Thanks for the suggestion, Zerro!). 

What worked well was decreasing the value of C38.  Changing from 100n to 82n gives takes the output voltage close to 1V.  I'll add a socket in the build and test out some values when I can hear the effect. 

Now what I'm wondering is if the slew pot is implemented correctly?  The B half of the pot effects the shape of the output signal, it warps the triangle slightly in the first part of the rotation then pushes it more towards a square wave around 50% of the turn.  The last half of the turn flattens out the signal completely.   The A half of the pot just cuts the input signal as it is turned up. 

I'm wondering what the function of the A half of the pot is?  My input signal was 2V, maybe the output from the Attiny is larger and the A is needed.  Any ideas?  I'm contemplating using a single pot instead of the double.