SV: Re: SV: Re: [sdiy] Moogey jitter

[karl dalen]

--- Magnus Danielson <cfmd at bredband.net> skrev:
> > > That would be great for analyzing a single VCO, it would not help very
> much
> > > when looking at it as it has passed through other circuits (such as VCF,
> VCA
> > > and other "sources" of "warmth").
> > 
> > I havent followed the AH hustle but isnt Kevins first statement 
> > that the warmth has its origin from the oscillators?
> 
> Well, personally I don't particular care about Kevins statement or not. I
> actually don't care about it being any other place either... rather I'm
trying to
> investigate what different "sources of warmth" is doing to the
phase/frequency >modulation, if  any can be  found that is.

I was late into the thread, not my fault everyone ""allready"" has debunked
kevins claims.
Still the thread title is Moogey jitter, and you are talking about your mini
etc and the
whole thread is based on some bogus stuff Kevin has claimed.

But Ok then, if we focus wheter a VCO jitter causes certain warmth or not 
here is one shot for you to try:

I say that its extreamly difficult to hear any difference between a VCO core
producing a sawtooth wave and run in singularity wheter it's a CEM , MS20,
ASM  ** whatever** core!  ( talking of the core, nothing else is involved
here).

However there is one significant source of difference in sound on a VCO core
and that's
if the comparator does multiple pulsing at reset/recharge. i.e when the reset
or charge
pulse from the comparator do a series of pulses instead of one single pulse.
The Moog
VCO *can* have this defect but is seldom seen, this miss behaviour in the LM393
is
mostly compensated by C18 and R34.(see Mini or any other Moog schematic). 

You can emulate this multiple pulsing, just do a bad comparator!
Make the switching tresholds slightely variable!

The sound difference experienced if the VCO are played in the higher frequency
regions a slight brightness and a slight dullness, lack of definition of bass,
if played in the lower frequency region, wich is exactly the ""opposite"" what
the Mini is said to have.

This multiple pulsing should be temperature and I bias dependant, also to some
extent
frequency dependant se LM393 datat sheet (the number of multipple pulsing
depends
on the capacitor C18 and gain R35) but i serioulsy doubth there is any multiple
pulsing
because if there was any the Rouge, Mini and the Prodigy VCO cores (examples).

0.002% jitter has absolutely minimal effect on sound compared to a small
fluctuation
on input levels to the ladder causes quite noticeable nonlinear distortion, or
for that matter
a badly balanced ladder causes way larger and constant nonlinear distortion
then any 
VCO core jitter.( sorry for that one, just a reference for comparing
differencies of 
sourches of warmth). 

Slow phasing between VCO's cause a plesant sound! What's new with that?

To test a VCO for its default phasing cabability, one simply dissconect the
expo
from the charge cap, then measures the time it takes for the VCO to complete a 
cycle, the longer the period the less current leak of the oscillator core.

Back to Kevins claims! ;-)

Why not doing the opposite, take 3 MS20 VCOs run it trough the mini VCF and VCA
then take the minis VCO run it trough the MS20 VCF VCA, i bet 3000USD that the
situation will be reversed in terms of Moogish sounding! ;-)

KD