[sdiy] 2164-based multiplier working

[David G. Dixon]

Well, after a complete redesign and new pcb layout (ah, the beauties of home
etching and drilling -- one day to completely redesign and rebuild the
board), my "multiplying modulator" based on the linearized SSM2164 is now
fully operational.  There was a tiny solder bridge sending my signal to
ground which gave me grief for about an hour, but I finally found and
eliminated it, and the circuit works perfectly.

Again, this little beastie swings from negative 2-quadrant multiplication to
4-quadrant to positive 2-quadrant with a pot, and has attenuators and
switches for positive, full, and negative polarity on both signal and
modulator inputs for interesting effects.  (Of course, if I'd really been
thinking, I'd have used negative-to-positive attenuators instead -- oh well,
the next time I build one perhaps.)  Now, it also puts out both positive and
inverted outputs as well (I had a spare opamp on a TL072, so what the
hell?).

If anyone is interested in the schematic, layout, simulation file, etc,
please email me offline.