Computer Audio Asylum

RE: Measuring accuracy - Jpp would be lower

65.19.76.104

In Reply to: RE: Measuring accuracy - Jpp would be lower posted by cics on April 03, 2008 at 10:53:03

What would the result be of such XO synchronization?

Without knowing the details of the circuitry involved I don't believe that it would be possible for anyone to answer your question. I think it would depend very much on the details of the circuitry and the causes of jitter in the two XOs, which would be things on the margin of the original circuit designs. In any event, if it were an obscure circuit design problem, it would be beyond my expertise, as I am a systems person and not a circuit designer.

However, I can take a guess. If the two clocks are synchronized then it becomes possible to consider that some amount of their jitter is correlated. The effect of this correlated jitter could then cancel to the first order. But if the clocks are not synchronized, then the correlated jitter would sometimes be additive and sometimes subtractive and how this appeared in the final results would depend on the method of averaging and the beat frequency between the two sample clocks. If there is no correlated jitter then I don't think it would make any difference whether or not the clocks were synchronized.

You can test for clock synchronization by measuring the relative timing accuracy of the two systems using a recording with two impulses separated by several minutes of silence. If the clocks are not synchronized, you will be able to determine the beat frequency of the sample clocks, which may be something to take into consideration in doing your averaging.

I will think about this some more and if I come up with something I will send you a private email.

Tony Lauck

"Perception, inference and authority are the valid sources of knowledge" - P.R. Sarkar

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