Let's Go Shopping

Voltage Controlled Oscillator

Let's Go Shopping



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.

NB: The Hardware Kit for the CGS348 matches the Compact Oscillator panel as shown at left. Consequently this Hardware Kit does not support all of the input/output/features offered by the design.

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.
PCB Dimensions: 2" x 6" with 3.2mm fixing points 0.15" from the edges
Power Consumption: +12V @ -12V @

Article, art & design copyright 2003 by Ken Stone

Email:  elby-designs@bigpond.com
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