Keeley Franken Screamer

[jculb69]

I was wondering if someone could explain the Keeley Franken Screamer mod with the additional footswitch and potentiometer for an added volume/crunch boost? I found this schematic and the description below. I don't know if it is accurate, but thought I would ask to see if someone knows how to do this mod. Thanks.

http://www.robertkeeley.com/images/Instructions/Franken%20Screamer.pdf

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Keeley replaced one of the standard clipping diodes with 2 1n4001 rectifier diodes in series. He used the stock switching circuit to switch the boost, wiring the fets as 1) across one of the 1n4001 diodes and 2) across the input and wiper of the boost pot. See illustration attached.