> I have a few Vactrols on hand Tim. Been experimenting with the
> VTL5C3 though, as it is "the fastest" of my choices.
>
> The Mod works, but it is not to my likings, and I think I might
> have to just buy the 146.
>
> I have tried several circuits to drive the Vactrol, but all seem
> to have too much slop in them, the response just does not feel
> right to me.
>
> Perhaps I have not tried the magic circuit... but I feel that
> more likely the 145 just was not designed with this type of
> control in mind!
>
> Thank you everybody for your help on this,
>
> Tony

We use exponential voltage controlled current sources in our vactrol modules
because of the double exponential behaviour of the vactrols. The current
source (instead of a voltage source) is needed as the LED illumination is
approximately proportional to the LED current (not to the LED voltage).

Best wishes
Dieter Doepfer