3080 VCA question

[Caloroso, Michael E]

> > > :::I always thought the Formant dual VCA a stupid solution as well.
> > > :::Maybe it is, maybe it isn't. I never tried the Formant dual VCA,
> > > :::but there is another dual VCA made from cascaded variable
> > > :::gm stages that sounds marvelous: The Minimoog VCA.
> > >
> > > In what respect does the cascaded VCA structure do anything good for
> > sound?
> > > Is it distortion?
> > >
> > > m.c.
> >
> > That's what I *think* it is, the combines "rounding" of the signal from
> two
> > cascaded stages. Which needs a special level matching between the 1st and
> > second stage, of course.
> > Haven't checked this for the Formant circuit. When I built a
> > Formant-inspired
> > synth long ago (my JH-1), I used a single exponential VCA.
> > Today I'd do it exactly as you described: One VCA with both lin and expo
> > CV inputs. For a general purpose VCA, that is. For a dedicated audio VCA
> > in a fixed architecture synth (VCA after VCF) you cannot beat the
> > "musicality"
> > of the Minimoog VCA scheme, IMO.
> 
I know I'm late with this...

The reason the Minimoog (and probably the Formant) has a second VCA is to provide control over overall volume, ala alternate controller (footpedal voltage control) or MIDI Volume CC Message.  The 1st VCA is controlled by the EG, the second is overall volume.  That's what the rear panel jack marked "VCA" is for, it's normalled to a fixed voltage to keep the 2nd VCA wide open.

The OB Matrix 6R uses the same technique.

MC
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