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Old 15th March 2004, 08:45 AM   #1
CJAVIER is offline CJAVIER  Spain
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Default Accuracy and Jitter

Hi,
Im looking for and oscilator to upgrade my CD Sony. I found some oscilators, but there are two concepts :
- Absolute accuracy : +- 50pp
- Jitter 3 ps

Can anybody explain me the accuracy stand for ?

Regards
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Old 15th March 2004, 09:33 AM   #2
OliverD is offline OliverD  Germany
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Accuracy means how far the oscillator might be off from the spec'ed frequency (long-term). A wrong frequency in the master clock will effect the pitch of the audio signal (a recorded 1kHz tone might be reproduced as 999.9999 Hz), but even the cheap standard crystal's specs are just too good to be concerned.

The jitter spec provides an information about very short-time inaccuracies (phase noise), which is much more audible. There are some very good threads with lots of valuable information on jitter. Do a search.

There are different kinds of jitter, and the total RMS jitter spec is usually worthless for evaluation. A CD player clock should be optimized by listening tests, as Elso Kwak did it. There is a schematic of his "Kwak clock 6" on the forum, and I suggest you consider it. It doesn't need exotic parts, and Elso even provides a kit and PCB (as I recall).
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Old 16th March 2004, 01:12 PM   #3
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Quote:
Originally posted by AMT-freak

There are different kinds of jitter, and the total RMS jitter spec is usually worthless for evaluation.

lower jitter = better

What is lacking in rms spec is

- sigma value
- spectral content

It is not easy to measure though

optimising clocks on perception may lead to a satisfying clock, but it does not have to have lowest jitter - it is just what you are after.......

cheers

Guido

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