[sdiy] Moogey jitter

[Ian Fritz]

Oooops, should have been clearer.  :-)

The first clip is in the phase cancellation region.   The two waves are 
subtracted, but they don't cancel well because of the jitter.  This is what 
I thought was supposed to sound warm.  We were told that even though jitter 
might be too small to hear directly it could provide warmth through phase 
interference effects. I agree with Harry, of course, about how it sounds.

The second clip is the SSM2033 chip.  There is broadband noise about 70 dB 
down from the fundamental.  Crank your amps up, and you should be able to 
hear it.  It sounds just a teeny bit grungy and jittery to me.

The third clip is the "good" VCO, a well stabilized tri-core design.  A bit 
of 60 Hz line intereference about 90 dB below the fundamental, otherwise no 
noise down to more than 100 dB.

JH -- interesting point about the servo loop oscillating.  I have some 
anomolous, weak sidebands in the spectra at 134 Hz, possibly due to the 
servo loop dynamics. I remember I had to fool with the decoupling a bit also.

   Ian


At 12:04 PM 4/20/06, JH. wrote:
> > The first wave sounds like sh!t
>
>Yes. Certainly not what I'd expect from a "warm" (whatever this is)
>VCO. I don't think the Korg Mono/Poly (SSM2033-based VCOs)
>sounds like this.
>
>BTW, I'm also using SSM2033s in my Minimoog Clone.
>I had *no* idea about what a Mini should be like, back then.
>(This was built before synth-diy started, I think)
>But I tend to like its sound. (The 2033 was a lucky choice.)
>I remember there were issues with decoupling the heater
>part of the chip, to prevent HF oscillations.
>
>JH.
>
>
> >
> > The second two sound the same to me...
> >
> > Warmth ??? BTFOOM....
> >
> > H^) harry
> >
> > --- Ian Fritz <ijfritz at earthlink.net> wrote:
> >
> > > Hello listers --
> > >
> > > So someone here told me that the beating of a
> > > jittery VCO with another
> > > would give warm phasing effects.  Well, I happen to
> > > have a jittery VCO in
> > > the form of an SSM3033 chip in my system.  The
> > > jitter comes from the
> > > temperature-control servo, as is easily verified by
> > > disconnecting the
> > > heater.  So I combined this wave with a wave of the
> > > same frequency from a
> > > "nice" VCO and made a wav file of the result.  The
> > > file also has separate
> > > sections clips of the individual VCOs.  Is this what
> > > VCO "warmth" is?  I'm
> > > asking seriously, since I really don't know.
> > >
> > >    Ian
> > >
> > >
> > http://home.earthlink.net/~ijfritz/temp/saws060418.wav
> > >
> > >
> >
> >