[sdiy] linear vactrol driver circuits

[Tom Wiltshire]

On 27 Jul 2009, at 15:56, Julian wrote:

>
> 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?

I don't know what other people do, but I've been experimenting with  
driving the LED in a vactrol with a PWM signal. This is supposed to  
give a more linear relationship between the driving signal and the  
LED brightness. I was using a microcontroller, but you could easily  
use a ramp or triangle wave oscillator and a comparator for an analog  
PWM solution.

T.