[sdiy] Polymoog resonator question

Ian Fritz ijfritz at comcast.net
Fri Oct 5 21:21:28 CEST 2018

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
> _______________________________________________
> Synth-diy mailing list
> Synth-diy at synth-diy.org
> http://synth-diy.org/mailman/listinfo/synth-diy

More information about the Synth-diy mailing list