CGS340 Compact VCO

Voltage Controlled Oscillator

This VCO started out life as a replacement for the original VCOs in Ken's '73 Serge, so it replicates a lot of the functionality of that module. Of course there have been numerous enhancements to the design as well, making it right at home in a 1V/Octave synthesizer. The core chosen is the well known Electronotes ENS-76 VCO Option 1 as used in the ASM-1, Modulus, etc. This core was an obvious choice due to the amount of information, lists of suitable substitutes and so on that are available on the web.

It has AC and DC linear CV inputs as well as 1V/Octave inputs and scalable/reversible CV inputs. It has sawtooth and pulse/square outputs, as well as a waveshape that is variable between sawtooth and a "sine-like" shape, and a fixed "sine-like" output too. It also includes a simple sub-oscillator for those who wish to experiment with that.

The sub-oscillator is based on that from an LM3900 application note (AN-72), but will not cover the full range available from the VCO core itself.

Note that the "sine-like" waveform is not a pure sine wave. There is a significant glitch in it that is almost impossible to trim out. As this is the recreation of a module that had such a waveshape, this is appropriate. If you require an accurate sine wave, this module is unsuitable for your purposes.

www.elby-designs.com/webtek/cgs/cgs348/cgs348.htm