I've modded these before and found I wasn't quite pleased, so I decided to incorporate the "fat mod" and add some more changes. I like to use it as a boost pedal for metal, and was never really satisfied with tube screamers.

Fat mod - change R6 to 150k resistor and R9 to 1K resistor.

What I added- Clip D5 clipping diode and change R17 to 1.5k resistor.

The fat mod thickens up the thin sound the DS-1 starts with. Clipping D5 kicks out a bit of gain and adds some volume to it can be used as an almost clean boost if wanted and has more controllable gain, though it warms the sound a little. Changing R17("treble blocker") lets more treble through and brittles the sound up a bit more to make up for the clipping D5.