ok. try not to kill me because i'm not an expert here, but done a lot of reading. The parallel cap attached to the fb resistor is doing what's called resonance in some amps. for further reading see tut 1 & 2. it's explained there. when you bypassed the feedback with a cap, you change the damping factor, making the bass looser. in this case the lows are limited by the cap, so it's a sort of attenuator, because they do pass through the 100k. Imagine you have an amp with feedback on the highs, but open fb circuit like an ac30 on the bass, that's the goal. i think i can scan the explanation from the book if you wanted. If you really want to have a flat freq response ot and eliminate possible ringings, what you need to do is a conjunctive filter. that's a resistor and a cap across the 2 sides of the ot. it's used by drz amps. i have a pdf paper somewhere explaining this and how to calculate it. let me know and i'll do the search in old back ups.
i did a lot of research in this, because i live in patagonia argentina, and can't buy ots here, so i have to wind my own using whatever materials i can find. so i used these artifacts to have better response from those ots...not a perfect world, you know, but i have a good tone out of my amps.
Bluesmaster CLEAN optimized for STRAT (Blackface cap values)
Moderators: pompeiisneaks, Colossal