Distortion Pedals w/ Treble & Bass boost: Pre, mid, or post distortion?
I haven't had luck pulling up schematics on pedals that have treble and bass adjustments to know if it happens pre or post distrotion circuit.
I imagine if it happens pre, you can get more or less distrotion on the highs or lows. If it happens at the distoriton circuit itself I'd assume the signal is split in order to have differnet distortion circuits affecting different frequencies. Post wouldn't be too special, just changing it before you dial it back down to a safe level for input to amplifier/next pedal.
Here's a schematic I found on diystompboxes.com. Not sure what's going on exactly but I'm thinking perhaps the "Tone" section at the end is their EQ, which implies that it occurs after the distortion is put in.
It's probably dependent on the pedal, though I would think most would have the adjustable tone section after the distortion circuit. After all, doing it before wouldn't prove much advantage over using your guitar's tone knobs, and the clipping will generally create harmonics that may or may not be useful, so a filter is usually put in afterward to help smooth out some of the harshness.
Some will have a hard wired EQ section. Something like a bass or treble cut before the clipping starts. I think the Tube Screamer has a HPF to cut the bass before it hits the first gain stage and then the normal tone stack after it. I'm not sure though. It's been a while since I've seen that schematic. Some pedals have more than one clipping section, so that would give you the opportunity to place an EQ in the middle. I think the Big Muff has multiple clipping stages, IIRC, but I think the tone section lies after both stages.