[sdiy] Ladder filter pole (Moog Taurus filter)

[mikko.a.helin at nokia.com]

Found the Taurus schematics here:
http://www.sonicstate.com/synthfool/schematics/taur1.gif
(also http://home.debitel.net/user/jhaible/jh_minotaurus_2.pdf looks much similar)

CA3080 is used only as differential amp (there's another for VCA), the output is buffered with a transistor to 4016 switch for resonance control. Would it be possible by varying the 3080 gain to control also the resonance by a CV? Obviously the output gain would also change at the same time but couldn't that be compensated in the VCA by subtracting part of the resonance CV from the VCA CV? That way you could get a really low part count VCF+VCA for polyphonic synth. How does that filter sound like (vs. mini/memorymoog filter)?
-Mikko

> -----Original Message-----
> From: ext Gene Stopp [mailto:gene at ixiacom.com]
> Sent: 18. April 2002 1:08
> To: Synth-DIY
> Subject: RE: [sdiy] Ladder filter pole
> 
> 
> Hey I thought it was a great pun!
> 
> I really like Moog ladders. They have a nice "sproingey" 
> sound when the
> resonance is turned up. Yes that's a tech term :) The only 
> one I've built
> myself was a copy of the minimoog filter, all 2N3904's plus 
> one 2N3906 for
> the expo converter. It even has the discrete output opamp. 
> Someday I'll
> build it into something.
> 
> I've been eyeballing the Taurus I filter too. Seems to be 
> even simpler, the
> output amp is a single 3080 so it has a real low parts count. 
> And we all
> know how these sound...
> 
> I've not seen the Memorymoog filter!! Any .pdf's out there?
> 
> Best Regards,
> 
> - Gene
> 
> -----Original Message-----
> From: John Blacet [mailto:blacet at blacet.com]
> Sent: Wednesday, April 17, 2002 2:17 PM
> To: Synth-DIY
> Subject: Re: [sdiy] Ladder filter pole
> 
> 
> I was confused by "pole" which is a term applied to filters of course.
> 
> "Poll" is a survey....
> 
> Da English Police  ;>
> ___________________
> John Blacet
> Blacet Research
> http://www.blacet.com
> 
>