Cheap ring modulator
don at till.com
Wed Mar 20 17:59:15 CET 1996
Date: Wed, 20 Mar 1996 14:20:34 +0100
From: thierry.rochebois at ief-paris-sud.fr (Thierry Rochebois)
I had an idea for a cheap Ring Modulator/VCA.
Pulse signal -------------+
Analog signal +-------+--O |
| | \ |
| |\ | +--+-----O out
| | \ | |
| / | |
When using an ADSR as analog signal, this simple circuit behaves like a VCA
(dedicated to pulse or square signals).
Except that VCAs are typically exponential.
Is there anybody who knows this circuit as part of an existing synth ?
Not to my knowledge.
Is it a good circuit ?
"Good" in a moral sense? :-)
It's okay in that it will work and it's slightly more flexible than an
XOR gate. But limiting one input to a digital signal just to save
money is pretty "user hostile" (opposite of "user friendly").
Remember that a 1496 modulator chip only costs about a dollar.
Typically a circuit like yours would be implemented as a variation on
the previously discussed +/0/- gain circuit, replacing the pot with a
single (SPST) cmos switch and a resistor.
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