Here’s a simple one that should fit nicely in a 1590a. EQD’s take on the Electra Distortion circuit. Instead of having a pot coming off the end of the circuit, the volume is controlled by a pot coming off the emitter of the 2N3904. It’s really more of a gain control than volume and if you wanted to, you could add a master volume control coming off the output. Who doesn’t love more knobs, right?
