MXR M181 Blow Torch

[stolen]

Hello everyone!

We still need to clean up drawing and verify stuff and we don't have means to measure caps atm, but long story short the blow torch is an OPA boosted Si NPN fuzz face (q9/10) with some modded values running at 18V. Torch button sets pre boost gain and there's a weird looking double transistor buffer (q7/8) between OPA and FF that we don't quite understand yet, maybe we missed smth or got it wrong? There's also a 2nd order passive filter after the FF/before the active EQ which boosts bass (fg unkown atm) and may or may not cut mids.

Will try to get more data/verification in but pretty sure this isn't worth a complete trace for us. Kinda annoyed at the 18V, we see no good reason other than EQ pad noise but it's an FF in front c'mon it's not like that's the limiting factor there.

Regarding the rumors that this has been used for some Marceline bass lines in Adventure Time: It does a good approximation of I'm just your Problem with some dry blend, but it could use some compression before and maybe a different bass (P maybe? we're using an EB3L). Didn't need the EQ much, and since it doesn't get you all the way anyways we think a vanilla FF with dry blend is a good DIY alternative (reference: watched some bass->FF vids, close enough).

Hope this helps someone!

[stolen]

Here's a mildly cleaned up redraw of our first tracing draft. Some component values and designators are missing. Notable are the 2 series resistors to bias Q9, there's no other unpopulated component or anything like a cap to ground to block AC, not entirely sure why they went for that. Also the output buffer misses DC reference, but likely we just missed that. Transistor types are guessed based on terminal voltages.

Edit: The output buffer at the bottom is U2A, not U2B. Also its output goes to TP1.
Edit2: Triple checked, Q7 really only seems to be saturated through the network that saturates Q8, not sure what they tried to do there.