[sdiy] Polymoog resonator question

Quincas Moreira quincas at gmail.com
Sat Oct 6 00:33:56 CEST 2018


David, great idea, there should be more resonators in modular, IMO.
I just reviewed the one Andrew of Non Linear Circuits designed based on the
Korg PS3100. Vactrols for Freq control, simple and juicy :)

https://www.youtube.com/watch?v=JdMPl-Pm5GM

Cheers!

Quincas




On Fri, Oct 5, 2018 at 2:24 PM Ian Fritz <ijfritz at comcast.net> wrote:

> Will this be a commercial product?
>
> > On Oct 5, 2018, at 12:54 PM, David G Dixon <dixon at mail.ubc.ca> wrote:
> >
> > Thanks, Don.  That's what I figured.  I have removed CD4000 switches from
> > many designs and replaced them with DG400 switches for that very reason.
> >
> > I'm going to redesign this Polymoog Resonator, using 2164s for the R's,
> > putting the stages under voltage control, and changing the output
> switching
> > situation a fair bit.  I'm still not sure what I'm going to do about the
> > loop gain situation.  I'm deriving the transfer function right now to
> get a
> > better idea of what it actually does.
> >
> >
> >
> >> -----Original Message-----
> >> From: Donald Tillman [mailto:don at till.com]
> >> Sent: Thursday, October 04, 2018 11:04 PM
> >> To: David G Dixon
> >> Cc: synth-diy at synth-diy.org
> >> Subject: Re: [sdiy] Polymoog resonator question
> >>
> >>
> >>> On Oct 4, 2018, at 9:57 PM, David G Dixon <dixon at mail.ubc.ca> wrote:
> >>>
> >>> I did have one other question, though...
> >>>
> >>> What is the significance of "V_CH" which seems to play the
> >> role of ground almost everywhere in the schematic?  Is this
> >> some specific voltage which is not 0V?
> >>
> >> Indeed, V_CH is 4.85 V.
> >>
> >> That audio section uses CMOS CD4000 series chips for audio
> >> switching.  Those max at 18V.  So the Polymoog runs the CMOS
> >> at 0 to +15V, and biases the audio signals up a little to fit
> >> in there.
> >>
> >> The alternative would be to leave the audio centered around
> >> 0V, and run the CMOS at something like +/- 5V.  Then all the
> >> logic lines would have to be shifted.  Which is a drag, but
> >> would have been better for audio quality.
> >>
> >>  -- Don
> >> --
> >> Donald Tillman, Palo Alto, California
> >> http://www.till.com
> >
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-- 
Quincas Moreira
Synth Diy Guy
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