[AW: VCA for LFO]

[Harry Bissell]

and Harry Bissell adds: The "analog multiplier" from the National
Semiconductor Apps Note AN-20 is a real good way to assure that the photocell
stays linear and stable... Ditch the lightbulb, its slow response will cause
servo loop "hunting". Use an LED instead.

I did this to control feedback in a SVF filter as a retrofit. :-)


Haible Juergen <Juergen.Haible at nbgm.siemens.de> wrote:
	> I hate to interrupt the computer discussions, but...

Thanks (;->)

	>What basic design(type) has the lowest CV leakage? In this
particular
	>instance, that would seem to be the most important criteria, as
noise would
	>have to get pretty horrid to cause any substantial problems, and
distortion
	>(for my purposes) is rarely if ever a problem. But if the center
frequency
	>of the VCO starts moving with mod amount, it's a bummer.
	>
	>I *am* working on the assumption that I want a linear VCA for this
function
	>(just want to be able to translate mod wheel info to my minimoogs).
Am I
	>wrong in this?

If you don't need fast response times for the CV, I vote for a vactrol.
No offset or CV bleedthru problems at all, and very linear / low noise.
Just not exactly fast ...
See MS-20 schemos for details.

JH.


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