[sdiy] voltage controlled filter???

[Theo]

The answer is in the name _voltage_controlled_ filter.
Can't do that to a pot, unless you use a motor servo to drive the pot. ;)
Modulation of the filter (envelope, LFO and even audio) are key elements of
synthesis.
Maybe get some time with a synth and play around with it.
There are several introductions to sound synthesis, you might want to read
up on the subject and try some your self.

HTH
Theo



----- Original Message -----
From: <synthplayer88 at spymac.com>
To: <synth-diy at dropmix.xs4all.nl>
Sent: Wednesday, January 05, 2005 4:40 AM
Subject: [sdiy] voltage controlled filter???


> Hi guys,
> I was wondering if anyone can tell me whats the different betwen using
> transconductance amp like the CA3080 and the LM13700 or the use of
balanced
> modulators/multipliers to control the cutoff frequency of say a state
variable
> filter, instead of dual rev log pot?
>
> Is is because dual rev log pot are hard to find?
>
> In order to use transconductance amp or multipliers don't you need to
generate a
> rev log voltage in order for it to work like a rev log pot?
>
> I am guess people are using dual gang linear pot wiring it like this
>
> http://home.comcast.net/%7Esbernardi/elec/og2/partsub_pots.html
>
> to get the rev log voltage then control a pair of the transconductance amp
or
> multiplier with it?
>
> Isn't it much straight forward to use a dual gang rotary switch  and work
out the
> resistance for cut off frequency?
>
> I guess my question is, why do people use VCF in synth? why voltage
controlled?
> For modulation prupose?
>
> Howcome I don't see people mention the use of balanced modulators, VCAs
and
> multipliers instead of the CA3080 and the LM13700?