[sdiy] linear vactrol driver circuits

[HARRY BISSELL]

Look at National Semiconductor AN-20, Analog Multiplier.

I'd try to match two vactrols, put the LEDs in series, use one
cell for feedback, the other for your variable resistance. It would
not be perfect but would greatly improve the linearity...

H^) harry



----- Original Message -----
From: Julian <julian at port23.co.uk>
To: synthdiy DIY <synth-diy at dropmix.xs4all.nl>
Sent: Mon, 27 Jul 2009 10:56:35 -0400 (EDT)
Subject: [sdiy] linear vactrol driver circuits 


Ive been considering using vactrols to add CV control, but am wondering what 
my best approach is for driving them.

Im thinking along the lines of a CV input jack, and a front panel pot, and 
an opamp mixer / driver for the led, but am wondering as to the best way to 
get away from the log response of the vactrol.

Im sure this must be a common issue when using vactrols, so im wondering 
what other people do?

Julian 

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