There are 3 factors involved here;
I. Master Clocks 10 Mhz 75 or 50 Ohm
2.Word Clocks which have to be manually switched to the frequency of the source recording e.g. 44.1, 48, 192 kHz etc.
3.Re-Clockers which reprocess and de-jitter a signal between the source and DAC. A re-clocker usually benefits from a stable signal from a Master Clock.
A clock without a linear and preferably regulated DC power supply is like a ship on the high seas, whereas a good power supply brings it onto dry land.
Imagine your family all used different clocks no one would get to school/work/whatever on time. All your digital equipment connected to the same Master Clock keeps everything in synch.