[sdiy] Env. Controlled 606 filter sweep methods?

[Happy Harry]

Using a FET or transistor as a Voltage Controlled Resistor is a tricky
proposition... I'd use a LED/Light dependant resistor (Vactrol). The problem 
here is that they are slow... maybe too slow for percussion.
They will react quite fast going DOWN in resistance... but slow in
returning to high resistance.

If you want a slow sweep of this parameter, this is the easiest solution.

H^) harry


>From: Plutonique9 <Plutonique9 at symbiocom.com>
>To: <synth-diy at node12b53.a2000.nl>
>Subject: [sdiy] Env. Controlled 606 filter sweep methods?
>Date: Wed, 28 Mar 2001 18:32:22 GMT
>
>I'm interested in adding the ability to sweep the internal 606 Hi hat
>and Cymbal filters by their associated Envelopes. I'm looking for a
>way to implement this in its most basic form, only a toggle switch to
>turn On/Off this function.
>
>Now with the BPF's, the cutoff is controlled by a resistor going to
>ground in a Op Amp configuration.
>
>I have been able to lower the cutoff of the HPF's by adding a
>resistor in parallel with a cap.
>
>So I guess, I would be needing a very basic Voltage controlled
>resistor. I'm thinking this could be implemented using a FET or
>transistor.
>
>All the same, I'm quite hazy in how you would implement this.
>Thankyou
>
>-- Plutonique9, Plutonique9 at symbiocom.com
>
>http://www.mp3.com/Plutonique9
>

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