Breaking down a schematic - Boss PW-2

liamon

Wondering if someone wants to have a crack at translating this schematic and decrypting what the knobs do. 

Annoyingly labeled “fat” and “muscle”, and the manual offers no help either. 

By my ears they are just a bass + treble function but wondering if there is more going on, or if my ears are wrong. 

https://elektrotanya.com/boss_pw2_powerdriver_overdrive.pdf/download.html

liamon

Also it’s often been compared to big muff. See a couple of diodes in there but the circuit seems way more complicated than a big muff and doesn’t seem to have the same double set of clipping diodes as you get in a muff. 

thermionic

At first glance I would wager that it has a lot in common with the BD-2 and OD-3, i.e., an opamp circuit built with discrete components.

ICBM

It's not really like a Big Muff at all, although it may be capable of some similar sounds. If anything a fair bit of it looks more similar to the FZ-2, although without the second transistor pair which causes the more obviously 'octavey' sound in that. It doesn't use clipping diodes at all, it's done by overdriving the transistors. The 'Fat' and 'Muscle' appear to be bass/lower-mid (around 120Hz) and mid (around 1KHz) tuned filters.

https://guitarpedalsvisualized.wordpress.com/2023/08/27/boss-pw-2/#:~:text=out around 1000Hz.-,It is a moderately wide Q (EQ%20cut%20width).,more%20like%20a%20Big%20Muff.