[sdiy] Moog wander

[Magnus Danielson]

From: René Schmitz <uzs159 at uni-bonn.de>
Subject: Re: [sdiy] Moog wander
Date: Tue, 18 Apr 2006 22:02:07 +0200
Message-ID: <444545BF.2070804 at uni-bonn.de>

Dear René,

> Hi Magnus and all,
> 
> > Well, for the moment I am only trying to measure and see what I can see. So far I am
> > really only measuring one VCO of one synth. I have plenty more to go (beating the shit
> > out of one VCO is quite meaningless). Then, when having a number of measurements at hand,
> > some form of actual analysis may be done. Until then I only notice various
> > characteristics without saying "this is it!".
> 
> Sure its wise to gather as much data as possible. What I'm saying is 
> that we need to correlate any of the findings afterwards to the 
> perceptional quality we describe as "fattness". Only then we can be sure 
> that whatever you may find is really the cause for this.

Indeed. I could not agree more. What I was saying was really that I am not even making
the assumption that I actually measure the "right" characteristics, only that I measure
some characteristics out of many. However, being able to measure them quite well should
certainly help to get some clarity, at least to the actual unstability of tune.

I do the measures since I sure would like to know what it is that makes these sensations,
and my gut feeling says that phase deviations (collective name for jitter, wander,
frequency drift, frequency unstability, frequency modulation, phase modulation and what
have you) can be a possible source and having a slight unusual stack of gear for the
purpose, why not put it into some use?

Weither we have a fuzzy trigger or whatever, it will show up. KD's post was very
interesting I might add.

> One criticism that applies to the whole Kevin vs. Kenneth debate is that 
> AFAIK neither did correlate the findings to the actual perceptional 
> qualtity. It could well be that there are varying degrees of µs scale 
> jitter in VCOs, but that they are inaudible and something else is the 
> cause. In which case the whole debate is "much ado about nothing".
> (IMO this is very likely so.) Likewise it might be for the wander aspect 
> of it. Only if an eventual hypothesis passes a test afterwards we can be 
> sure.

When reading up on the jitter tolerances correlated with professional audio (revised
recommendations in AES-3id I beleive, and the articles leading up to that) shows that
for certain frequencies, jitter well below 1 us may be audioble, just by considering the
amplitude of sidebands etc. Most interesting reading and quite seriously done. Not the
normal sales-gibberish at least.

> Besides, is "fattness" really the same as "warmth", I don't think so.

There is another issue. It may not necessarilly be the same, but for me they have at
least been somewhat related.

Cheers,
Magnus