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In Reply to: RE: USB clocking for 44.1k? posted by Dynobot on March 04, 2017 at 08:47:39
Hi,
> Is it possible to slave the USB Bit-Bucket clock and the Audio
> Bit-Bucket clock to 'one' master clock?
That is called "Asynchronous USB Audio".
It actually does not directly slave the clocks (that is not possible in that sense), but it makes sure the audio clocks determine audio timing.
Modern mixed signal system routinely have multiple clocks and the wide variety of clocks needed does not make synchronisation across all clocks feasible.
The important part then becomes to make sure each individual clock is correct for the job and performs adequately and that the audio conversion uses one high quality clock after a short memory buffer (to handle any data flow control).
Ciao T
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?
Follow Ups:
For some reason I was thinking someone could use something like this Black Lion Micro Clock MkIII XB, to sync up their digital from end [Rpi for exampe, their USB card and their Dac's internal DSP processor...or everything else. Provided, of course, that these items had the proper connection....likely a DIY project, but should be doable.Not Feasible??
Edits: 03/06/17
Hi,
> Not Feasible??
Not really.
You can sync the audio clocks, but Async USB operates the audio section from a local clock anyway and the USB clock is needed for the USB operation and not directly linked to the audio side.
It probably is worthwhile for you to truly understand how Asynchronous USB works and what the implications are. This article may be of help:
http://www.edn.com/design/consumer/4376143/Fundamentals-of-USB-Audio
Ciao T
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?
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.
Hi,
> 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:
http://www.soundonsound.com/techniques/does-your-studio-need-digital-master-clock
Ciao T
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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