Diefet - Diezel VH4S Simulator

With 7 pots this was never going to be put in a 1590B anyway and so I wasn't so concerned about keeping the size down, although I bet it could fit in a 125B and would be very impressed if someone did it. :o)  I think most people will opt for a 1590BB though.

This is a project from techniguitare which has gone through a number of revisions over the years, with this version based on their 18V version of the circuit.  Use the trimmers along the middle of the board to bias each JFET drain to half the supply voltage.  The bottom right trimmer seems to alter the frequency of a high pass filter after Q3, and so will cut some low end.  This wasn't in earlier version of the schematic which instead just had a 100K to ground, but I can't speak French and so maybe someone could tell me the reason for its inclusion.