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In Reply to: RE: USB clocking for 44.1k? posted by Thorsten on March 05, 2017 at 20:30:32
Modern mixed signal system routinely have multiple clocks and the wide variety of clocks needed does not make synchronisation across all clocks feasible.
Interesting, it was my understanding that recording studios routinely used one Master clock to sync everything.
Maybe I misunderstood.
> Interesting, it was my understanding that recording studios routinely
> used one Master clock to sync everything.
> Maybe I misunderstood.
Maybe, instead of trying to understand how such systems work, you merely took away what you wanted and ignored most?
You cannot slave/sync the USB (or Wifi, or Ethernet etc. etc.) Clock directly to studio clocks, for the simple reason that the clock frequency is wrong.
The job of the "House Clock" is to synchronise the audio (and often video clocks) of multiple converters, so that multiple devices do not loose "sync".
You can see the need when handling Video & Audio using separate converters. I think you can also appreciate the need if we (say) use three stereo ADC's to make a six channel recording. Each individual Quarz Crystal in a given oscillator will have a frequency that is just a tiny bit different. So if we wait long enough, they will no longer be synchronised.
So while the need to synchronise clocks is obvious, there is a dirty little secret in that. Most Pro-Audio devices perform notably worse on external clocks, than when running on cheap internal crystals.
And of course on top of that any non-audio clock in the system (e.g. USB, Ethernet etc.) will not be synchronised to the audio clock.
You may find this article useful on the studio perspective:
At 20 bits, you are on the verge of dynamic range covering fly-farts-at-20-feet to untolerable pain. Really, what more could we need?
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