I made sure its not amp OD by testing over the Direct Montitor on my audiointerface. Also the distortion it produces sounds way more unpleasantI just built this and was just testing it out. I can get unity gain with volume at 12 o’clock. As I increase the mids, my amp goes into a soft overdrive, which I think is working as intended. It’s a “Strat fixer” type of pedal, I like it a lot. The switch doesn’t seem to affect the tone too much for me, not sure if it’s very subtle or I goofed.
Maybe my pickups are just way hotter than yours. With my Humbuckers I cant even get to unity gain when I want to increase the mids by a good amount (on 9V that is). Scooping works better.
Also I am runnig it on 18V now as suggested, which works better.
But I am glad it serves you well! Lets hope it still works when you fixed your switch