Came across this design in researching a different project and thought I’d draw it up. It uses 3 transistors and doesn’t take up a lot of space, so you should be able to fit it in a 1590A or add it to another pedal. More info can be found here. Sounds like you can use pretty much any medium-high gain PNP/NPN pair for Q2-3 (2N5087/2N5088, BC560/BC550, etc).
