The FemtoSecond Clock Measurements
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 Femtosecond Clocks have amazing noise performance with a guaranteed jitter measurement at the worse case of 1 Hz to 1Mhz away from the ideal clock frequency of less than 33 femtoseconds (0.033 picoseconds). We are making 4 clocks with various jitter specs.
Here are our measurements on our top two at 24.576 MHz:
- MSB CLOCK MEASURED: Galaxy Femto 33
- Phase Noise at 0.1 Hz -67 db -72 db
- Phase Noise at 1 Hz -99 db -114 db
- Phase Noise at 10 Hz -134 db -145 db
- Phase Noise at 1 kHz -157 db -157 db
- Phase Noise at 10 kHz* -157 db -170 db
- Phase Noise at 100 kHz* -157 db -170 db
- Guaranteed TIE (1Hz - 1Mhz) 77 fs 33 femtoseconds**.
* 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.