Something of a classic and many other designs are based on the MXR Distortion + so no real need for an introduction.

MXR DISTORTION PLUS – VERO LAYOUT

DISTORTION PLUS ANALYSIS

There’s an excellent analysis of the Distortion + here on Electrosmash including a schematic (be prepared for some maths)

Note that I have used alternate pot values, compared to some of the schematics out there.   There’s evidence to support this on DIY Stompboxes.