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In Reply to: RE: GPS audio master clock posted by eduardoo on July 25, 2012 at 03:16:00
Except for a few (rare) broadcast applications there is absolutely no benefit to using a GPS clock or atomic clock for audio. There is no need for playback to take place at the exactly correct rate and pitch, as it wasn't recorded that way and a tolerance of 0.1% is more than adequate.
The devices are made for laboratory purposes and output 10 MHz. This requires using a frequency synthesizer (including a phase lock loop) to generate the clocks commonly needed for audio. This process will unavoidably add jitter compared to a local free running clock, and hence sound quality will be degraded through use of these clocks.
About the only exception might be streaming applications for continuous operation where low latency is required, such as broadcast audio of sports events. If the streaming source and the receivers were both locked to the same time base then it would be possible to avoid an occasional buffer glitch every few hours. In practice, there would still be glitches caused by Internet glitches, so this "improvement" might not even be noticed.
Tony Lauck
"Diversity is the law of nature; no two entities in this universe are uniform." - P.R. Sarkar
Follow Ups:
Thanks, Tony, for the informative post.
I would think that the frequency synthesizer would take away the benefits of the accuracy upstream, too. Interesting idea anyway.
No, a correctly implemented frequency synthesizer will preserve the long term frequency (timing accuracy) from the GPS or atomic clock. There will be short term variations, but these will get cancelled out. So if you are using one of these puppies to run a clock, it will keep constant time, until the next leap second. :-)
Tony Lauck
"Diversity is the law of nature; no two entities in this universe are uniform." - P.R. Sarkar
If it can keep the accuracy of the GPS, wouldn't it be possibly be better than most internal clocks of CD players (although my Esoteric already claims pretty high accuracy at +/-0.5ppm)?
These specs say nothing about jitter. One can have accuracy without low jitter. It's a case of accuracy without necessarily having precision.
Tony Lauck
"Diversity is the law of nature; no two entities in this universe are uniform." - P.R. Sarkar
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