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AM2430 Module - Ring Modulator
Overview The Eľ Modular has a rather nice Ring Modulator based around a pair of dual transistors. It has both DC and AC modes and can therefore create a wide range of complex tones.
A clone of this circuit would be rather expensive because of the cost of matched transistor pairs, so I have based this module on the MC1496 balanced modulator chip, which is at the heart of many Ring Modulators from the 1970's (e.g.
Roland 100 and 700 Modulars). Maybe I'll clone Dave's transistor design in the future.
A ring modulator accepts two inputs (carrier and modulator) and produces the sum and
difference frequencies of them. For example, if two sine waves of 100 and 150 cycles are input, the output will be two frequencies - 50 cycles (150 minus 100) and 250 cycles (150 plus 100).
Waves with many partials,
such as rectangular or sawtooth waves, create very complex output signals. Ring modulators enble metallic sounds, bells and klangs to be created.
Original Circuit
The Eľ Ring Modulator is based around two matched pair transistors, and it has input attentuators as well as DC and AC modes for both carrier and modulator.
New Circuit
The AM design is a typical implementation of the MC1496 implementation, with attenuation on both inputs and AC/DC mode switches that switch 1uF capacitors in and out of the signal paths.
I have added a dedicated LFO for modulation purposes. Square and triangle waveforms
are available, and the frequency range can be set low or high. Patching in a modulation source will disconnect the internal LFO.
Panel
The front panel is a standard AM design, 90mm wide and 4U high, with black lettering. Controls knobs are standard Eľ Modular designs. The LED is a high intensity 5mm blue, mounted in a LED clip. My prototype panel is 80mm wide so that it fits alongside my 100mm Darkstar module.
Build History The schematic and board were laided out with Eagle CAD, and the PCB was manufactured by Olimex.
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Resources
* Front Panel .fpd file
* MP3 Demo