--- Dieter Doepfer < hardware@... > wrote:

> From: "Dieter Doepfer" < hardware@... >
> To: "Bakis Sirros" < synth_freak_2000@... >
> Subject:
> Date: Tue, 14 Oct 2003 11:13:37 +0200
>
> Bakis, please forward ....
>
> > This is both true and not true. The basic filter
> circiut will have
> > the same sound. What makes it sound different is
> the response time of
> > the vactrol. A vactrol is basically an LDR and an
> LED facing each
> > other and encapsulated in black plastic. Since
> they are put together
> > in a non precise manner, not every vactrol will
> behave the same. So
> > the response times will vary, hence the difference
> from one filter to
> > the next. The difference will be marginal and not
> widely different.
>
> It is not only the response time but the fact that 2
> or more vactrols do not
> generate the same resistance with the same LED
> current. For applications
> with only one vactrol (e.g. VCA, 6dB filter) this
> does not matter but for
> applications with more than one vactrol (e.g.
> filters with more than 6dB,
> phasers) where the tracking of the resistance is the
> assumption for the
> circuit. E.g. a 24 dB filter requires 4
> simultaneously changing resistors
> and the 4 resistors should vary as close as possible
> to obtain the ideal
> function. But very often the non-ideal behaviour of
> a circuit cause the
> special unique sound (e.g. Moog transistor ladder,
> Wasp filter, diode
> filter, and so on).
>
> Dieter Doepfer
>
>

=====
Bakis Sirros
Parallel Worlds / Polariton
Athens-Greece
1 group owner
http://www.rubber.gr
http://www.ward12.com

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