[sdiy] Moogey jitter

[Ian Fritz]

At 11:54 PM 4/17/06, elmacaco wrote:

>I am not a moog religous zealot, I merely want to see this explored. I
>understand digital recording quite well, I don't think moogs have magic,but
>I do suspect that you need to have the module to make measurements of it.
>What sound card was used to record the mp3 of moog oscillators?  I've
>recorded for days at 96kHz 24 bit audio, and it still sounds different than
>the saxophone or singer that just sang, there is a change, and depending on
>how fast the effect we are talking about is, it will be at least distorted
>by recording.  You may be aware that jitter in digital clocks in soundcards
>can also distort the recording, good enough for rock and roll, but you must
>admit that a recording is not just as good as the real thing, it is one step
>removed.  It would be considered a secondary source.

Well, I would say that this is the crux of the matter.  I believe that if 
there is a strong and obvious amount of jitter in a signal then a digital 
recording will capture it adequately.  After all, isn't Kevin's video 
digitized?  If there is such a large variation in the signal as the video 
shows then it seems to me that it would have to show up in a wav 
file.  (And Kenneth's is a wav file, not an mp3, as you state.)  Analysis 
of Kenneth's file does show that there is some jitter, just not as much as 
suggested in the video.

I agree, of course, that digital recording has imperfections and 
limitations.  But measuring the zero crossings of a strong steady signal is 
a perfectly valid method of looking for timing variations on the order of 
milliseconds, which is what Kevin claims to see.  Note that in the SMPTE 
collection of suggested measurement techniques for jitter there are methods 
involving digital scopes, but there is nothing similar to Kevin's measurement.
<http://www.smpte.org/smpte_store/standards/pdf/rp192.pdf#search='jitter%20measurement'>


>Someone please lend Eldhart a moog and some oscilloscopes so we can do this
>without fighting.

I'm sorry, I must have misunderstood.  I thought Kenneth's file came from a 
Moog.  The early part of tha AH thread is apparently lost, so I didn't get 
to read it.


>A file is not an oscillator, digital recording is by definition a distortion
>of the actual signal, dots then connected, there is information lost, it
>might be valueable to this discussion, it might not be, but that information
>is lost is undeniable.  If I had a moog 901-B I'd give you 192kHz 24bit
>files, and information would still be lost, but wouldn't you rather have it
>there to hook up to your scope?

No, I would not.  :-)

My scope cannot measure jitter.  It can tell if there is some present, but 
it cannot do an acceptable measurement.  Much better to analyze the 
digitized data.


>a recording may capture it, it might not.  To find out what it is in the
>circuitry that is causing or even simply effecting the sound one needs to
>examine the circuit.  I think the idea that the power supply can affect the
>sound of an oscillator isn't such a daft idea.

Sure.  But remember that Kevin tested his modules using a stable lab 
supply, not a Moog supply.


>How much and if it is
>audible needs to be determined further since it is so controvercial now, but
>I don;t think moog warmth is magical, it sounds good, and no one can explain
>it satisfactorily.

OK, it sounds good to you.  Does it sound good on CDs or just live?  :-)

   Ian