This board acts as a clone of the CEM 3374 VCO IC used in analog synthesizers from the 1980s including:

• Fender Chroma Polaris
• Oberheim Matrix 12
• Oberheim Xpander
• Akai VX600

This board works the same way as the circuit in the original CEM3374 ICs, so it sounds almost identical. (Three out of six of the VCOs in my Chroma Polaris are using these, and I can't tell any difference in sound) It is designed to operate with 12V for Vcc and -5V or -6V for Vee, which is what all of the synthesizers listed above use for supply voltages. The circuit contains two oscillator channels with triangle and sawtooth wave outputs. Triangle wave outputs have an amplitude of 1/3 Vcc, and sawtooth wave outputs have an amplitude of 2/3 Vcc. Synthesizers using the CEM 3374 that generate square/pulse waves do so with external comparator circuits.

Channel A sync is implemented. Channel B sync is not implemented, but this feature was rarely used on the CEM 3374 (None of the synthesizers listed above use it).

A thermistor circuit is used to provide a temperature compensated reference voltage. Typically, this voltage is used as a reference for the DAC that outputs the voltage that controls the frequency of the oscillators.

This was tested on a Chroma Polaris. It wasn't tested with any other synthesizers, but it should work in all of the other synthesizers listed above. Changes made for rev 1 were specifically done to make these compatible with Oberheim synthesizers. Please contact me first if you are planning on using these with an Oberheim synthesizer or Akai VX600.