I did not design the schematics myself. Since my objective is to make this preamp portable, I searched for the simplest preamp design and found this from www.redcircuits.com
. This is called a "Solid-state Fender Blackface Preamp", which is a transistor version of the original valve circuit from the "Fender Blackface".
I then borrow the tonestack from the Tonemender that is found at www.runoffgroove.com
. The Tonemender is a booster with a very flexible tonestack, which can re-create the Fender, Marshall and Vox responses.
Details of these schematics can be found at the links above, which explain clearly what these circuits do and how they work.