The initial breadboard build.
Powered with + 15 v - 15 v switching power supply. One cv input for LFO or ADSR Envelope modulation and one cv is being used in attempt to offset the initial voltage to 0 volts = off = silence.
The pin outs on the two little mini jacks were mis labeled by SparkFun, so it took a little probing around to discover that the node labeled "tip" was not actually where my signals were coming out of these jacks. After this hurdle was surpassed, I discovered two resistors that needed to be in serial, rather than in parallel, and then bingo, the circuit came up and met my expectations.
Perfboard prototype. Power Header and IC sockets. I have added a 2nd 8 pin IC socket for the second op amp that I will be incorporating into the build to make the module a dual VCA.
Bottom view. Soldering it together. Things start off really tidy at first......
Perfboard completed. Top View. Laying out the components correctly and soldering them in place without shorts or faults was a tremendous step forward for me. When first plugging in the board to my modular system, it didn't work. After tracing the signal path with an oscilloscope I was able to identify the fault and remedy a fix for it.
Three jacks for Signal Input, Control Voltage, and Signal Output.
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VCA - Transconductance Op Amp LM13700
VCA build with an LM13700 transconductance op amp from Ray Wilson's Make: Analog Synthesizers book.
Future Enhancements:
* Add a 2nd VCA - In Progress
* Solder basic circuit onto perfboard - Completed
* Add power supply decoupling circuitry - Complete
