Per request. The switch can be replaced with a tone control. Just omit 100k resistor at column 17 and replace the switch connections with the lugs of the 100k tone control.
Electro Harmonix Little Big Muff – transistor version
Tools, Tones and Toys for Guitarists
Per request. The switch can be replaced with a tone control. Just omit 100k resistor at column 17 and replace the switch connections with the lugs of the 100k tone control.