[sdiy] jitter analysis

[Czech Martin]

> That the ear is band limited to 20 kHz or there about does 
> not mean the
> resolution at lower frequencies is limited to 50us steps. 
> Well, it could be,
> but it doesn't follow from the band limitation. So even a 
> small jitter could
> be (at least subliminally) perceptible. In my understanding 
> (which could be
> completely wrong), band limitation says nothing about the 
> resolution within
> the pass band.


I'm pretty sure that this is wrong. We know from the properties
of frequency transformations (Laplace or Fourier or other)
that delta t ~ k * 1/delta f.

That is: any system that is band limited to f can not have better
time resolution then k* 1/delta f. k depends on the actual 
transform, but it doesn't really matter.
So, a very rough estimation is, that any system limited to 22KHz
can not have better then 50us time resolution.

It is simply another version of Heisenbergs unvertaincy principle.

We do not have to argue about the real limitation of the human ear.
At some frequency all perception will be lost. My ears can go as far
as 16-17 kHz, others may reach 22kHz. But not much more.

My assumption is that the noise component which is interesting here
is very low in frequency, < 10Hz.
After all, we do not percieve those waves as noisy, but drifting.

As long as the sampling system goes down to DC, I assume there is no problem.

btw.: I expect that very old transistors have a lot of 1/f noise,
and also shot noise. New transistors have improved a lot, simply because
of general semiconductor advancements over the last 40 years or so.
This would mean that replicas with new hardware are not the same!

http://astronomy.swin.edu.au/~pbourke/fractals/1onfnoise/
is also interesting for experiments.

m.c.