[sdiy] Linear vs. Exponential control of VCA's

[The Old Crow]

On Thu, 16 Aug 2001, Scott Bernardi wrote:

> I guess my question is, what are people using in their systems? What
> do some of the old classic systems (Moog, ARP, OB, etc.) use? Has
> anybody ever done any comparisons?

  The Yamaha CS line uses a VCA that has both linear and exponential CV
inputs.  In nearly all cases the expo input is used for an offset
trimmer/CV reject trimmer.  The linear inputs are attached to the EG
outputs, panel controls (for things like aftertouch VCO mod depth, etc.),
touch response detectors, and so on.  I would love to make a SMT micro-PCB
equivalent of the IG00151 at some point.  Yamaha's precis on the chip is
not very informative, but from what I can tell it is just an OTA with a
simple linear V/I and simple expo V/I summed together to the Iabc of the
OTA.

Crow

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