Sorry I confused you!
When I was talking about the first and second op-amp I was only referring to IC1. IC2 prepares the signal for the digital tuner and possibly the headphone output, can't exactly remember.
Make sure to understand the channel switching, which is hard with my schematic.
So just referring to IC1, the first dual(2) op-amp, the second part of that op-amp is actaully a buffer with gain of aproximately 2.
After the signal exits the second op-amp, IC1 pin7, we see the single diode(that how it was in my Micro-Crush). The reason I say make it a symetrical pair, instead of just a single diode, I that pure IC distortion is usually termed 'harsh' and that's been my experience too. By having a pair of clipping diodes, the signal becomes more natural, tame, and pleasing(maybe).
There are two common areas to put clipping diodes: in the feedback loop (TS style), or after the op-amp's output (not as popular, example the MXR Dist III).
So this circiut takes after the MXR Dist III, but the major difference is the MXR III has two clipping diodes after the first op-amp. The Micro-Crush has the clipping diode(s) after the second op-amp (IC1 pin 7).
Well I hope you're not more confused. Lets move on to feedback of the first op-amp(pins 1, 2, and 3 of IC1).
Understanding the switching here is critical. On the clean channel, switch pin 3 is not connected to anything so the 1M resistor is the feedback to ground resistor.
Read the basic rules for calculating gain of op-amps (this how I know anything analog, EE classes have me on digital for now):
http://www.allaboutcircuits.com/vol_3/chpt_8/4.htmlShort summary: Op-Amp Gain = feedback-resistor (divided by) feedback-resistor-to-ground
Example in second op-amp: 2.2K / 1K = gain of 2.2
My computer's acting strange so I'll wrap up(finally!). Increasing the 2.2K feedback-to-ground-resistor to 5-7K will have almost zero affect on the clean channel, but will significanly change gain when in overdrive channel.