For the two decades I've been dealing with digital audio, I've always understood that "word clock" and digital audio were two different entities. One focuses on the AD/DA converters, the other deals with the subject matter "audio". Word Clock just keeps the sample rate for the converters in line or sync'd, so that the audio stream won't get any audible artifacts such as clicks, pops, aliasing, etc.
My understanding is that any digital device has a clock: PCs, Macs, drum machines, samplers, microwave ovens, etc.
The clock is supposed to keep calculations in sync, and not just at the AD/DA stages.
The better the clock, the less jitter (lack of precision). This is why some audio engineers pay big money for high end clocks like the Antelope atomic clock.
The sounds is clearer, more focused, tighter, more defined, the soundstage is usually larger, the bass goes deep without getting muddy, the high end is more refined, etc.
For example, you can run the same ProTools session with the same DA stage and hear differences when switching clocks (I’ve tested it for myself).
So, the MPs definitely have a clock that has an impact on the sound and I was curious as to listen to them slaved to an external one.
But there is no evidence so far that this is possible.
ADAT and AES digital audio are able to carry the clock signal alongside the audio, which SP/DIF doesn’t (thus, probably, the WC option on the SP/DIF card).
It seems to me that the 4k was designed to function as the master but not the slave.