[sdiy] VCO Jitter, Slop ... (was: Re: Smith's Evolver Desktop's spikey VCO waveforms)

David G Dixon dixon at mail.ubc.ca
Mon Jun 10 21:49:42 CEST 2013

I'm going to go just a little bit further than Andre and state that I think
all this talk of VCO jitter is complete bullshit, unless someone can prove
otherwise with soundclips and scopeshots.

> -----Original Message-----
> From: synth-diy-bounces at dropmix.xs4all.nl 
> [mailto:synth-diy-bounces at dropmix.xs4all.nl] On Behalf Of 
> Andre Majorel
> Sent: Monday, June 10, 2013 9:57 AM
> To: synth-diy at dropmix.xs4all.nl
> Subject: Re: [sdiy] VCO Jitter, Slop ... (was: Re: Smith's 
> Evolver Desktop's spikey VCO waveforms)
> On 2013-06-09 03:00 +0200, Michael Zacherl wrote:
> > On 9.6.2013, at 00:11 , Andre Majorel wrote:
> > 
> > >> VCOs suck.  That's why they're interesting.
> > > 
> > > I can't prove it but I'm pretty sure it's their jitter that makes 
> > > VCOs interesting, more than their waveforms. For human ears, all 
> > > waveforms are equally boring if perfectly periodic.
> > 
> > if you had to put it into numbers, what would be the amount 
> of jitter, 
> > you think?
> Hi Michael. Don't know. I experimented with modulating the 
> frequency of an MS-20 VCO with white and pink noise. As the 
> FM sensitivity knob was turned clockwise, it went from no 
> audible effect to unpleasantly warbly. I couldn't find a 
> setting that made it sound "even fatter" or anything like that.
> My guess is that there is a rather narrow range of jitter 
> between "sterile and brittle" and "blurry and weak" and by a 
> happy accident, the state of electronics in the sixties and 
> seventies led to VCOs which fell right in the middle.
> Recently read a very interesting bit about how much mains 
> frequency ripple there is on power rails inside synths. Wish 
> I could remember where and who.
> Some years ago, Scott Gravenhorst posted here an MP3 of one 
> of his digital synth projects. I thought it sounded 
> surprisingly good (i.e. not DCO-like). He said he used a 
> small amount of pink noise FM on the oscillators. Maybe he 
> could tell us more.
> > et al ... and, in general, something like a slop parameter on DSI 
> > synths for their oscillators, is that just for the 
> frequency and how 
> > much? Never had a play with it.
> Since you can hear the difference between VCO and DCO on a 
> single note, I don't see how temperature drift & scaling 
> errors could be the source of "fatness". They may contribute 
> to it, but they're not the essential ingredient.
> --
> André Majorel http://www.teaser.fr/~amajorel/ 
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