[sdiy] simple vcf

[patchell]

    Your options for tuning a VCF are somewhat limited.  You need an element
whose conductance will change with voltage.

    Of hand, diodes, transistors (ladder filter), photo resistors are some of
the options.  I supose you could try the voltage variable capacitors (this is a
diode designed with a lot of capacitance).  Another methode is pulse with
modulated resistors.  I did one of these a long time ago.  Interesting sound,
strange sidebands.  You can also do some very interesting things with diodes.
Wish I could remember what I did with this article that was in a real old EDN
magazine.

Gavin wrote:

> Hey all,
> I'd like to build a real simple VCF, it doesn't need to track a VCO, just do
> sweeps based on an input control envelope.  I'd like to develop a design
> that doesn't use OTA's.  Has anybody seen or worked on anything like this?

--
 -Jim
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