[sdiy] Irwin dual VCA--any interest?

[Tim Parkhurst]

> -----Original Message-----
> From: synth at charlielamm.com [mailto:synth at charlielamm.com]
> 
> I got my first 4 "dual linear VCA a la Michael Irwin/EDN magazine"  PCB's
> back from APCIRCUITS.  I put a dual VCA together last night, fired it up,
> tested it, and it worked great--no trace cutting or last second fixes
> necessary--at least not that I have discovered yet--thank goodness!
> 
> The PCB is based on this article:
> 
> http://www.reed-electronics.com/ednmag/contents/images/72502di.pdf  scroll
> to the bottom of this PDF--that's the one I mean.
> 
> Mr. Irwin's design idea has a lot of things I like: it's simple, low parts
> count (less to go wrong), sounds good (_truly_ linear, so it sounds smooth
> and satisfying when responding to an AR or ADSR's attack and release), and
> is flexilbe (I esp. like being able to "program" the reference control
> voltage with a single DC voltage below ground....)
> 

So I'm thinking, where do we want a linear VCA, and where do we want an expo
VCA? Do we want linear if the VCA is being used to control/attenuate a CV?
I'm also assuming (at least for audio uses) that a linear VCA sounds best
when driven by an expo source, and a expo VCA sounds best when driven by a
linear source. Right? (and by "sounds best" I mean smooth, natural sounding
changes in volume without abrupt or uneven changes)

Tim Servo



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