Here is another filter commonly found in hifi amplifiers that I adapted it for use with 9v single supply and guitar signal. In the middle of the tone pot it is almost completely flat and to one side it boost below the center frequency and to the other side it cuts. It also works great as a treble booster or a bass booster (depending on how you set the level), both as a stand alone unit or after a low output fuzz. :)
I recommend putting the level/gain pot outside the box insted of a trimmer in this one.
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