5th July 2009
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#4 |
| Lives for gear
Joined: Jun 2009
Posts: 3,397
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According to Lucid, they have better jitter than Big Ben.
From e-mail: Quote: A quick bit about jitter specs and why we (and most others) don’t publish them. First off, there is no standard way of measuring jitter. Since there is no standard, comparing between brands then becomes meaningless, unless the two companies use the exact same test and method…not too likely. Second, if a company gives a jitter spec in print, another company can see what the “number to beat” is, and do whatever test (in whatever way) will produce a number that is lower, regardless of how the clock ACTUALLY performs. It’s kind of like power amps….my car stereo doesn’t really produce 45W in each of the four channels of the little amp that’s built in.
So, we did our tests as fairly as possible, same day, same method, same test, same cables, with normal production units, etc. We needed to know how we stood up, and the short answer is, very well.
Jitter measurements were made using the Stanford 610 Universal Time Counter. Jitter is expressed (in seconds) as the Mean Allan Variance of 10,000 measurements of the positive edge-to-positive edge period of the input clock, running at the frequency indicated. Arming mode is External-Time, positive edge. Both devices and the Stanford counter were allowed to warm up for at least 30 minutes prior to taking the measurements. Both devices used the same inputs and BNC cable, terminated at the counter with 50-ohm termination.
The word clock signals were generated internally by each device.
Word Clock Frequency | GenX192 MAV Jitter (picoseconds) | Apogee Big Ben MAV Jitter (picoseconds)
If you have any questions, I’d be happy to discuss the results on the phone.
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