[sdiy] Simple VCA?

[Andre Majorel]

On 2008-04-12 20:52 -0400, John Mahoney wrote:
> At 03:00 PM 4/12/2008, mike ruberto wrote:
>
>> The simplest VCa out there is the Yamaha single transistor design. I
>> think you can find details about it on Mr. Haible's website.
>
> I was thinking it was a Korg circuit. High control voltage
> feedthrough is it's main problem, if memory serves.

It's noisy too. On paper, it's a very bad VCA. In practice, it
makes a wonderful audio VCA if you can live with the thump on fast
envelopes.

>> Using an FET optocoupler is also a simple VCA solution.
>
> How about using a Vactrol? (I know they are slow, but aside from
> that?)

The light-dependent resistor exhibits a memory effect. The same CV
will not yield the same resistance depending on what CV you have
applied for the past minute. It's hard to use for control voltages
if any kind of precision is needed.

-- 
André Majorel <URL:http://www.teaser.fr/~amajorel/>
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