Layout drawn from schematic posted here
"This is a multipurpose effect: buffer/line driver, clean boost, and the interesting part is a tone control that works by varying the input impedance. It's aimed at pedal steel guitarists, whose instruments seldom have a tone control and often no volume control. Instead, most steelers use a volume pedal and adjust their tone with the amp tone controls. This effect provides a handy tone control and boost in one enclosure."
I adapted the spdt on/off toggle to a dpdt stomp switch so the effect could be bypassed.