[sdiy] single transistor VCA (was OTA VCA)

Ben Bradley ben.pi.bradley at gmail.com
Sat Mar 25 00:49:26 CET 2017


I don't see that a bipolar transistor, whether NPN or PNP, could work
in any reasonable way in such a circuit without giving lots of
distortion. If lotsa distortion is okay, you can do about as well by
varying the bias current through a signal diode. For a large quantity
cheap (at least a lot less than using OTAs), use a JFET as a variable
resistor, as in the Rod Elliot VCA article.

On Fri, Mar 24, 2017 at 7:04 PM, Justin Herrmann <ebn303afxcut at email.com> wrote:
> You may have already come across this in your VCA research, but Rod Elliot
> has a good VCA page with all the circuit topologies I've seen:
> http://sound.whsites.net/articles/vca-techniques.html
>
> And Nikka Bergfors has a VCA comparison page with actual measurements:
> http://hem.bredband.net/bersyn/VCA/vca_shootout.htm
>
> Justin



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