By popular demand, here's the PAL 800, a well regarded Marshall-in-a-box circuit. Should fit nicely in a 125B. Schematic here. All the trimmers except the one just below the Volume control are for biasing the JFETs. Start at 4.5v on the drain of each JFET and adjust by ear from there. The other trimer is for smoothing out the output signal.
Had a couple questions about stompbox use with line level, so I drew up this. This allows you to drop the line level signal down to instrument level, send it out to whichever stompboxes you want to use, then back and amplified back up to line level. Schematic and discussion here. Made two versions, one that could be run off typical +9v pedal power, and another for bi-polar 12v supply used in Eurorack synths, so you can build it either in pedal form or Eurorack module form.
