That explains exactly what I was referring to as "slop" Dieter. I was using a current source.

I might try something along those lines, as I am interested in learning more about using vactrols.
Still, the VCLFO you sell would fit in my system (if I removed the 145) and it is very nicely priced!

Thanx again,

Tony


----------------------------------------

> To: Doepfer_a100@yahoogroups.com
> From: hardware@...
> Date: Mon, 7 Jan 2008 10:01:14 +0100
> Subject: AW: 1 Re: adding CV to A-145 LFO
>
>> 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
>
>
>
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