This is a compact VCA (Voltage-Controlled Amplifier) unit that operates without any additional external components. Its small form factor — approximately 22mm × 10.5mm — makes it ideal for integration as a submodule in larger synthesizer projects. The module features seven pins arranged in two rows with a 2.54mm pitch, spaced seven pitches apart. It is also compatible with standard breadboards..
The unit has been tested with a ±12V symmetrical power supply. Basic specifications are as follows:
- Input signal range: -8V to +8V (recommended: -5V to +5V)
- CV range: 0V to -8V (unity gain is achieved at approximately -4.6V)
Below is a simple usage of the module. The NPN type takes negative CV. The PNP type will be released later.
Output offset at -5V CV that gives near unity gain would be around 20 mV without trimming the unit.
If smaller offset is required, put a trimmer pot to the opposite side of the input. Put some CV such as -5V with zero input. Adjust the RV1 to make the output 0V.
The repository includes KiCad project files, along with the symbol and footprint for the unit.
The schematic:
