[sdiy] very simple VCA circuit

[Naoki Iwakami]

If you have so many VCA's, how about using analog switches and a
triangular oscillator that make PWM chop?
Roland vocoder VP-330 does it to provide row of VCA's.
It's very linear and simple though you might need rebuilding all the VCA's.

-- Naoki

On Fri, Jan 28, 2011 at 12:35 AM, David G. Dixon
<dixon at interchange.ubc.ca> wrote:
>> > why not the CA3080 of LM13600/700 ?
>> > OTA have reasonably low component count, good to very good performance.
>>
>> Sorry, but I can't accept this w.r.t. the CA3080. That chip doesn't do
>> anything that I'd qualify as "good performance". If you're lucky, it'll
>> stretch to "acceptable performance". Mostly it's noisy with obvious
>> feedthrough.
>>
>> Still, it probably compares pretty favourably to the one-transistor VCA
>> that Justin suggested, though I've never tried that. And I do agree with
>> Harry that the question is "how good does the VCA need to be?".
>
> First of all, thanks for all the great responses.  Definitely food for
> thought.
>
> The deal is, I'm working on a new VCA design which has 8 VCAs in it (all
> 2164), and I need a ninth, so I didn't really want to add another 16-pin
> chip just for a single VCA.  This VCA only needs to vary the gain of a
> control voltage from 1 to 2 depending on a certain other voltage.  The
> control voltage itself will control the depth of FM modulation, so it
> doesn't need to be too high-performance.  Also, since it is going into a
> linearized 2164, it's confined to positive voltages, so one transistor would
> work well.  I'll definitely check out the "one tranny" solutions in the
> WP20, etc.
>
> _______________________________________________
> Synth-diy mailing list
> Synth-diy at dropmix.xs4all.nl
> http://dropmix.xs4all.nl/mailman/listinfo/synth-diy
>