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modDemod
This circuit was originally utilized in the generation of Single Side
Band Modulation; a military developed Radio communications
technology. A program (speech, data) would be mixed with a high
frequency carrier waveform using this circuit. After filtering an RF
amplifier would be used to broadcast the transmission. At this point
the signal could be said to be Modulated, sounding unintelligible. At
the receiving end, this circuit could again be used to Demodulate
the radio transmission by re-introducing a carrier waveform of the same
shape and frequency used to create the transmission. As you can
imagine, some cool distortions happen on account of the inadequacies of
this technology, variation in the two carrier waveform generators
(both frequency and shape), signal levels and of course, interference.
reclaimed for artistic purposes by
Harold Bode (and perhaps others) reclaimed this technology for artistic purposes in the early 1960's (utilizing carrier waveforms in the audio range instead), and Bob Moog (in collaboration with Bode) incorporated it into his Modular Synthesizer Systems in the 70's. By then the design was pretty different and they were calling it a "Ring Modulator" possibly for the "diode ring" configuration originally utilized or perhaps they knew it was a more appealing name that, to some degree, described the clangorous, bell like sounds a single iteration of the circuit was capable of creating.
The
modDemod features 2 identical circuits that may be used together or
individually. When using them together there is no need patch the
output of circuit 1 to the input of circuit 2 as they are internally
patched when nothing is inserted at the output of circuit 1 and the
input of circuit 2. I worked very hard to minimize carrier bleed. The
amount varies from unit to unit and even circuit to circuit
within each unit. HOWEVER, all units match or better the level of bleed
you hear in most IC based ring modulators. For this type of circuit,
that is very good!
To use this module you will need a minimum of 2 signal sources. 1 will
be the Program. This signal is inserted at the Program input (sockets 1
or 4). The 2nd is the carrier, and it should be inserted at the carrier
input (sockets 2 or 5). The outputs are at sockets 3 and 6. By varying
the Frequency, Shape and level of these signals, many different timbres
may be heard.