My Zombie Screamer is really good for heavier overdrive sounds but I wanted to design a simple overdrive that had a wide range tonal control(treble boost and cut), that could be used as a simple clean boost…through light overdrive….. all the way to heavier distortion. It uses junk-box type parts and is easy to get up and running. The only part that is a little unusual is the 5k tone control pot. I say this because ideally, it would have an anti-log taper. A linear pot will work fine. I like the sound and it can be tweaked in a number of interesting ways. Decreasing R3- will increase your max overdrive level, you can go to just two diodes instead of two sets of series diodes for clipping, R10 can be made larger( softer clipping) or smaller(harsher clipping). The tone control can be modded also. You can swap the pot connections to C6 and R8(wiper will now go to C6 and the high side connection will go to R8). This changes the curve some. Another option is to tie C6 to the top of R8 and then connect c9(you may want to adjust this value) through the tone pot(as a variable resistor). This only gives treble cut but the overall gain is higher giving more intense distortion.
(more drive for low output single coil pickups)
Yet another version which is hybrid FET/Transistor
(best range of overdrive)
Surface Mount Circuit Board: