Looking For Filters

[Matthew S. Padden]

Hi..

Mark wrote:
>
>I've been considering getting a stand alone filter box like a Waldorf
>X-Pole or Mutronics Mutator, but they seem rather pricey.  So I am looking
>into the possibility of building my own VCF's.
>
>Although a kit would be easier, I'm not opposed to etching my own PCB's.
>Are there any VCF schematics or sources of schematics out there that any 
>of
>you would recommend??  I would like to include several different filters 
>in
>the same rack, including at least one 24db and one 12db resonant LPF.  I
>would like to have all of the modules run off of the same power supply
>(which I'm suppose would be +15/-15).
>

Well, I found myself in precisely this situation last year. I decided to 
build a small set of Digisound modules, which would give me the same 
functionality as a Mutator, but also be capable of many other things. Price 
wise (over time) the difference may not be that great, but you find 
yourself with a lot more features and a great deal more flexibility.

Having found a nice 6U Eurocard rack frame, I decided on the following 
module complement (the model numbers may be wrong):

2x DG80-7 state variable 12/24dB VCF, using SSM2040 ICs
2x DG80-4 24dB VCF, using CEM3320 ICs
2x DG80-10 VC Envelope Shaper, using CEM3310 ICs
1x DG80-9 Dual VCA, using CEM3330 IC
2x DG80-?? Envelope follower
2x DG80-2 VCO, using CEM3340 ICs
1x DG80-?? waveform multiplier OR ring modulator

So far the DG80-7 VCFs are finished and sound superb. The DVCA and VCES 
modules are almost complete (money is tight! :) ). There is also space in 
the rack for the Digisound +/-15V PSU built round the 723 regulator.

So, my advice would be: roll your own! :)

Hope this helps
--
Matthew S. Padden
Computer Music Research Group
Room M5/14
Music Dept.
Huddersfield University
Queensgate
Huddersfield
England HD1 3DH
p: +44 1484 422288 x2402
f: +44 1484 472656
e: mattp at mindless.com
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"The masses are asses and need Tonto's glasses!" (Mark Mothersbaugh)
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