a few people who caught the concert at theaterlab on sunday made remarks about the above piece of handmade equipment, so i thought i'd explain it in this post.
ring modulation, theoretically speaking, refers to the multiplication of two signals. in a software system, depending on your context, the same term can sometimes apply to somewhat more complex operations such as the product plus the sum of two signals. some software synthesis environments, such as supercollider, have a bevy of ring modulation operators, since the mathematical implementation may change depending on the intended application.
the preserves jar contains the original ring modulation circuit. the term 'ring modulation' in fact comes from the diode ring through which the signals pass, after going through center-tapped transformers. this particular ring mod uses two fairly high-quality, vintage transformers, and the diode ring is made from four vintage germanium diodes, desoldered from some ancient piece of gear. my source for parts is richard matthews, bob seer's tech, who works out of a massive unmarked garage in greenpoint. love that guy.
while i can't tell you exactly what it does from a mathematical standpoint, i can tell you that it's not any of those definitions i mentioned above. germanium diodes have a particularly crunchy sound to them, which is why they are so sought after for distortion circuits. i don't think i could satisfactorily model this effect in software.
n.b. the carl sagan recording introduced some weird buffer artifacts, so while it still sounds cool, the sinewaves do a better job of demonstrating the effect.