The 3209 is a dual VCA module

This description comes from the Series 3000 Modular Synthesizer Instructions Manual.

The control PCB is the standard Synton board. Both potentiometers are linear.

This is a simple module with a single quad op-amp and a dual OTA.

This reference diagram shows the values of the parts.

This diagram details the calibration.

Operation

Operation is straightforward. Here are three photos of the VCA driven by different waveforms.

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