[sdiy] VCA response - continously variable between linearand exponential

David G Dixon dixon at mail.ubc.ca
Sun Mar 3 20:21:48 CET 2013

You make a good point, and I've built many VCAs with Expo/Linear switches.
I personally almost never use the Expo mode.  However, the exponential mode
is useful (other than when being driven by linear envelopes) for percussive
sounds or for just giving some "pop" to amplitude envelopes, but pure
exponential can be very harsh, giving a sharp spike in gain right at the end
of the envelope.  In that case, it's nice to be able to temper the
exponential response a bit with some linearity.

> Ha!
> I totally forgot about the Emily Litella character, or at 
> least the name, but I get it now. I totally missed the boat 
> on the VCO / VCA distinction. Usually I catch myself before I 
> write an entire essay.
> But in an attempt to save a little face, isn't exponential 
> VCA response an attempt to cater to the human hearing 
> system's perception of intensity as a logarithmic function? 
> We hear volume in relative terms, not absolute. Decibels are 
> logarithmic, and almost perfectly map to our perception of 
> intensity of sound.
> In other words, I again ask: Why would you want anything 
> besides linear or pure exponential? Something in between 
> doesn't seem terribly useful. (not that a synth designer 
> shouldn't create additional parameters for variation)
> Brian
> On Mar 2, 2013, at 19:36, David G Dixon wrote:
> >
> > I think we're having an "Emily Litella moment" here:
> >
> > We're talking about VCAs, not VCOs!

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