VCO design

Michael Zacherl mz at
Fri Jun 2 10:26:34 CEST 1995

> Are you familiar with the Chroma VCO design? Quite interestingly, it's
> based on the RC4151 V-to-F converter which allows for good linearity
> characteristics. A minor drawback with this design is the relatively
> long retrace time (20 us), during which the output is forced to gnd.
> This slightly alters the saw shape (-> harmonic structure) at high
> frequencies. I've used this design for my VCOs, and it works well.

That's one of the reasons for the Chroma's typical sound (As far as I cab tell from my 


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