Title sounds strange but hear me out on this one.
I built an OCD circuit (on vero) and when you reach a certain point on the gain knob, the bass gets kinda heavy and mushy. This is a cool sound in it's own way, but I was curious if there was a way to tighten it up. I used to own an EHX OD GLOVE (OCD clone) and IIRC it had the same behavior.
I believe what's happening is that when the gain hits a certain point the op amp is overloaded (saturated, op amp clipping), and that is what's generating that heavy bass sound. The mosfet clipping removes the harsh op amp clipping, but the eq change (heavy bass) remains. One suggestion is to run the pedal at 18V, which does reduce this significantly (op amp rails are higher, so it doesn't saturate until later).
My idea was to put RED LED's in a soft clipping configuration across that first op amp. This clipping will prevent the op amp from being saturated, but you don't necessarily hear this soft clipping. The mosfet clippers should hard clip the signal below the threshold of the red led soft clipping. The difference is you don't have that heavy bass since the op amp wasn't saturated.
I applied this mod to my OCD build and it works quite well for tightening up the bass at higher gain levels. The sound is somewhat similar (not exactly the same though) as running the unmodded circuit at 18V. I recommend putting this mod on a switch since the bassy sound at 9V is still cool.
Let me know if anyone tests this out, or has any comments (or corrections) about the theory here. At some point I may revisit this on a bread board to be able to test and verify more thoroughly the behavior of the op amp clipping in this circuit.
I built an OCD circuit (on vero) and when you reach a certain point on the gain knob, the bass gets kinda heavy and mushy. This is a cool sound in it's own way, but I was curious if there was a way to tighten it up. I used to own an EHX OD GLOVE (OCD clone) and IIRC it had the same behavior.
I believe what's happening is that when the gain hits a certain point the op amp is overloaded (saturated, op amp clipping), and that is what's generating that heavy bass sound. The mosfet clipping removes the harsh op amp clipping, but the eq change (heavy bass) remains. One suggestion is to run the pedal at 18V, which does reduce this significantly (op amp rails are higher, so it doesn't saturate until later).
My idea was to put RED LED's in a soft clipping configuration across that first op amp. This clipping will prevent the op amp from being saturated, but you don't necessarily hear this soft clipping. The mosfet clippers should hard clip the signal below the threshold of the red led soft clipping. The difference is you don't have that heavy bass since the op amp wasn't saturated.
I applied this mod to my OCD build and it works quite well for tightening up the bass at higher gain levels. The sound is somewhat similar (not exactly the same though) as running the unmodded circuit at 18V. I recommend putting this mod on a switch since the bassy sound at 9V is still cool.
Let me know if anyone tests this out, or has any comments (or corrections) about the theory here. At some point I may revisit this on a bread board to be able to test and verify more thoroughly the behavior of the op amp clipping in this circuit.