C2 allows mainly mids and highs through into the clipping section.The R1 limits the signal going into the opamp and R5 sets bias for the opamp.This leads itself to a bit of a fuzzy compressed tone with not much volume left over after being clipped. The Dod OD250 and YJM308 circuits are almost identical to this and these mods will work for these pedals as well.Here some of my favorite mods that I like to make to this type of circuit: Here''s the schematic with the mods in place: These mods will make your pedal into a much bigger, fuller, nicer (or meaner) sounding distortion or overdrive.
The MXR Distortion ("Distortion Plus") is a distortion pedal originally designed in the 1970s by MXR Innovations.
This is because it is changing the frequency response of the opamp at the same time.
With the gain control all the way up it only clips frequencies 723hz and higher, though it is at max gain.
Thom Yorke of Radiohead has included the Distortion for many of his signature distortion sounds, using a variety of guitars to achieve various tonal options.
Rowland S Howard (The Birthday Party/These Immortal Souls/Crime & the City Solution/Solo albums) also used this pedal across his career.