Build it up last night and it works - so it's verified now
Acts more like a somewhat dirty boost on a clean amp, but adds a nice punch when on the drive channel of my Lionheart - sounds great! Fits in a 1590a easily.
Tested 1N4148 and green 5mm LEDs - both work, but for now I prefer 4148. Volume was reverse, layout is now updated.
Fun little quickie!