A simple, but good sounding light overdrive. None of the parts are critical, but a high-gain transistor is recommended. Also, adjustment of the 68k resistor may be required to get approximately .9 volts at the collector.
If desired, a 1k linear pot may be used in place of the 680-ohm resistor, with the 22uF capacitor attached to the wiper. This makes a good gain control. A 100k volume control may also be added from the .1uF to ground, with the output taken from the wiper.