[sdiy] VCO Linear FM input - DC or AC coupled?

Ben Riggs benalog1977 at gmail.com
Mon Jun 26 20:28:42 CEST 2023

So assuming you’re talking about the FM input commonly placed into the summing node of the op-amp servo for the expo-converter?

The capacitor, as well as removing any DC, also removes any possible DC temperature dependency added to the expo converter.

This may or may not be important.


> On 27 Jun BE 2566, at 00:31, Neil Harper via Synth-diy <synth-diy at synth-diy.org> wrote:
> hey everyone,
> i noticed some vco schematics have a dc blocking cap on the linear fm cv
> input and some are directly coupled.
> is there any advantage to either? AC coupled seems to block out the
> possibility of really slow FM modulation with an LFO - or at least makes
> the response not intuitive.. so I can't really see the point.
> --
> /// Neil Harper
> /// Every Wave is New Until it Breaks
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