[sdiy] Moogey jitter

[Ian Fritz]

At 12:05 PM 4/16/06, Antti Huovilainen wrote:

>Another problem with single waveform comparison/analysis is that ear is 
>not very sensitive to small spectrum amplitude / phase / frequency 
>differences. However, once you mix two or more oscillators, these errors 
>translate to dynamic errors in the beating a (notch filtering basically) 
>which is much more easily audible.

OK, so I just did this...a sort of audio bridge measurement:

I recorded an inverted sawtooth from one of my good VCOs at a frequency 
very near to the one on Kenneth's file.

Then I took the first digital waveform section from Kenneth's file and 
lined it up in my multitrack editor with the inverted saw so they cancel at 
the middle of the section.  Then I mixed them into a new wav file.  This 
file has narrow negative pulses at the beginning, procedes through 
cancellation and then ends up with narrow positive pulses.

Next I did the same thing with the Moog section from Kenneth's file.

Now if there is all this interesting beating from phase jitter that people 
are suggesting, then the results from the Moog file should show it as an 
irregular progression through the beating region.

But no, the progression is again quite regular and sounds (to me) the 
same.  Makes sense, no?  How much effect should a 0.2% jitter have, anyway?

Conclusion:  Any phase beating effects are going to occur over longer time 
scales due to drifting and wandering, not the bogus phase jitter that Kevin 
claims.

   Ian