This is an Ugly Face by Tim Escobedo. I think the sound is pretty good. It makes a sort of pulse width modulated square wave via the guitar signal driving a 555. Not for every occasion. But the sound it makes it makes well. I really like this thing, so much in fact that I’ve made 3 so far.
Here’s a layout that would fit in a B sized box.
Here’s a modification of Tim’s original scheme that adds a blend knob. The blend knob mixes between the signal coming out of the 386 and the signal coming out of the 555. This adds an extra knob to the build, which makes for a pretty tight arrangement. The 16mm pots would work. But, 12mm pots with 1/2″ knobs would work well. Something like this at Mouser.com These pots are the same as the typical pots but they have a 12mm diameter body. A 1/2″ knob is about the same diameter.