The Dirt Transmitter is dual transistor crumbling fuzz tone. The bias control affects the voltage to the transistors which can create super cool gated velcro fuzz when turned counter clockwise or bring it back to life by turning it clockwise. It's "properly biased" around 2 o'clock on the dial. Adjusting the tone with the bias is a must to achieve a wide range of sounds. The fuzz control can produce tones from overdrive like break up to all out thick ripping fuzz tones while never getting flabby. Excessive amounts of volume and virtually no extraneous noise. Works great with both single coils and humbuckers, clean up with the guitar volume is excellent.