Bastl3r wrote this instructable detailing the build of his guitar booster pedal project:
I chose an overdrive pedal design off of generalguitargadets.com (Schematic) and modified it like this:
- added a simple positive/middle/negative supply
- added a noise filter I found on beavisaudio.com right after the DC Jack (Huminator)
- took away the clipping diodes on the output
- connected the diodes in the feedback path directly
- added the switch to change the resistance of the feedback path (10k <->30k)