2131 VCO

A Saw, Triangle, Pulse VCO based on the Sound Semiconductor SSI2131 chip. Fully built and ready to use.
Manufacturer: Infinite Machinery

The 2131 VCO is a 1V/Octave VCO based on the Sound Semiconductor SSI2131 chip. The module offers unparalleled temperature stability, exponentiality, waveform integrity over a 10 octave range.

Manual Controls

Coarse Tuning - Approximately 5 octave range

Fine Tuning - Approximately 1% frequency adjustment

PWM - Controls the pulse width or duty cycle of the pulse waveform output.

Hard/Soft Sync - Switch changes between hard and soft synchronization of the sync frequency input.



2 1V/Octave inputs. Voltages are summed together.

PWM CV - Externally controls the pulse width or duty cycle of the pulse waveform output. This input is summed with the manual PWM control.

Sync frequency input. Toggle switch switches between hard and soft synch operation.

Linear FM - A ground-referenced current input. Current into the LIN FREQ pin sets the linear scale of the exponential converter’s output. It can be used for linear FM applications.


Internal Adjustments

Bias - Provides a base output frequency. Normally adjusted to output a frequency of 27.5Hz

Scale - Exponetial scale tracking adjustment

High frequency - High frequency tracking adjustment

PWM CV Range - DIP switch for setting max PWM CV voltage. Normally set to 5V. Push switch to upper position to allow up to 10V CV inputs. This switch is accessible from the front panel, through the small opening below the Hard/Soft synch switch.


Every 2131 Oscillator comes pre-calibrated to track 1V/Octave. Re-calibrating the SSI2131 is relatively simple procedure.

We provide a web application to assist in calibration - SSI2131Tuner  Follow the instructions on the page to calibrate your 2131 VCO

See the SSI2131 datasheet for more information about the SSI2131 VCO chip and its characteristics. 

SSI2131 Datasheet.