[sdiy] 3280 VCA question

[The Old Crow]

On Fri, 30 Mar 2001, Kenneth Martinez wrote:

> I was breadboarding a 3280 VCA, copied from the final voice VCA of the
> Prophet-5...
> 
> I've got it working, but I don't understand the function of Q410 in
> controlling Iabc - what does it do, since its base is connected to
> ground?  How does this resistor-transistor-resistor setup differ from
> just connecting a single resistor?

  That is a linear voltage to current converter.  The OTA is a
current-controlled device; to control it with a voltage you want to
convert the voltage to a current.  I think Jim Patchell has some pages
about using the CA3280.

Crow

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