Pigtronix Fat Drive

Here's an interesting one from Pigtronix. It uses a TL072 to push a CD4049, which is followed by another TL072 pushing a Rat-esque tone control. All the gain stages make for natural compression and tube-like tone without using clipping diodes. Schematic for reference on FSB here (note, I've linked the inputs of the unused stages of the CD4049 to +9v to avoid any unwanted noise). Runs great on 9 or 18 volts and will fit in a 1590B with board mounted pots.