Here's Bjorn's Baby Blue overdrive. Fairly straight forward JFET circuit with hard clipping in the 2nd stage. The clipping diodes in the original are (massive) 2A1200s, but other silicon diodes will work–socket and experiment. The JFETs used in the original aren't confirmed, but I've laid it out for GSD pinout. Pots are board mounted and should fit in a 1590B. More info here.
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Also, I've added extra holes on the PCB for the 470nF caps in case you want to use electrolytic capacitors.