Doepfer - A-114: Dual Ringmodulator
Module a-114 contains two separate ring modulators. a ring modulator outputs the product (multiplication x & y) of the signals at inputs x and y. it's similar to a vca, but whereas a vca only responds to positive voltages at the inputs (2-quadrant multiplication), the ring modulator responds to both positive and negative voltages (4-quadrant multiplication).
the ring modulator thus provides a refinement of amplitude modulation (am). ordinary amplitude modulation will output the original carrier frequency fc as well as the two side bands (fc - fm, fc + fm) for each of the spectral components of the carrier and modulation signals - but ring modulation cancels out the carrier frequencies, and just lets the side-bands pass to the output.
a ring modulator is used for the production of bell-like sounds, alien voices, or just to produce new timbres.
this module has a maximum current draw of 40ma. it requires 4 te/hp worth of space to fit in a eurorack frame.