Marshall’s Classic early fuzz circuit which famously offers ‘more bass’ than its close contemporaries, for a thicker sound. In the late 60's and 70's players would often go through dozens of fuzz pedals to find a unit biased to their liking or intended use. With the addition of a Transistor Bias control, today’s player can achieve multiple great tones simply running the sensitive PNP Germanium transistors hot or cold. Adjust the Bias pot to go from spitty to smooth to spitty again with many great incremental effects in between.