[sdiy] Using DG-series analog switches for PWM VCA

Tom Wiltshire tom at electricdruid.net
Wed Jun 13 14:52:44 CEST 2018

> On 13 Jun 2018, at 12:21, Mattias Rickardsson <mr at analogue.org> wrote:
> 2164 VCAs accept supplies down to at least +/- 4 V, so it shouldn't be a problem. They do show roughly a doubling in THD compared to the +/- 15 V supply according to the SSI2164 data I've seen so far, but that shouldn't really be any problem in a pedal. :-D
> The PWM switch solution *might* be a better solution (for several values of "better") considering you already have access to the digital control for switches but perhaps not the analog CVs for VCAs, but certainly feels like a more complex solution when coming from analog. Do it! ;-)

Yes, “several values of ‘better’” sums it up pretty well. I’ve already got a uP in the design, so producing the PWM control signals no big deal - what R.G.Keen ironically calls “a simple matter of programming”. And the filtering isn’t going to add much either, since there would already be an op-amp buffer on both ends, and those can easily be modified into filters instead. So I think I shall try it.

That said, as long as you don’t need battery power, I suppose the 2164 at 9V is ok - “within spec” at least, and it’s probably operation beyond that limit to some extent. Perhaps I’ll save that for something else.

Thanks all,

       Electric Druid
Synth & Stompbox DIY

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