The Mojotone JFET Boost Kit is a simple drop-in boost that can fit in the smallest pedal boxes or drop right into your guitar. The kit produces around 16db of boost. The JFET boost can be overdriven by other pedals, just like the front end of an amp, producing a nice tube breakup. Runs on 9v - 18v.
JFET Boost Wiring Diagram