Clock measurements are a tricky thing. Comparing clock measurements is nearly impossible. Everyone quotes the lowest jitter numbers they can, which are the time interval error show in this textbook illustration below. But this error is very frequency dependent so usually this number is quoted for a very high frequency, where the clock is very good. They do not mention the jitter at lower frequencies where clocks are not so good, and where jitter is more relevant to audio sound quality.
A more useful measurement is phase noise. Phase noise shows clock jitter in the frequency domain. We look at the undesired power of the clock at various frequency ranges away from the primary clock frequency. The red lines in the actual clock measurements below show the noise 1 Hz away from the clock frequency. This specification is very relevant to audio performance.
The MSB Galaxy Clock has amazing noise performance with a guaranteed jitter measurement at the worse case of just 1 Hz away from the ideal clock frequency of less than 77 femtoseconds (0.077 picoseconds). OK, so here is another pretty unbelievable jitter specification. We better stop right here and share our ideas about specifications.
Here are our measurements at 24.576 MHz:
* at CMOS output levels (For reference, at normal +13 dB levels the noise would be -170 dB).
** Calculated on the web site JitterTime.com
The MSB Galaxy Clock must be installed very close to the DAC or ADC as jitter increases with distance. We can help you design the best interface for your product.
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