Re: [Jack-Devel] Ethernet-based audio interface using (net)jack idea

Thanks for the info on the TC DICE chip John - I've been checking it out,
and also noticed that the JetPLL 'code' is available on license. Of course
that would add expense, so I understand why you would use just that part of
the chip for the timing. As yet, I've not found 'the' JetPLL chip (if they
make it), so I'll dig a bit further into TC's website.

The abilities of even the DICE mini chip are impressive, and somewhat
relevant to this project. It's definitely worth keeping in mind!

Whilst doing a bit of Googling, I came across this manufacturer:

http://www.vectron.com/products/vcxo/vcxo_index.htm

Would some of their ICs be of use for this project? I can't find the price
of a DICE chip, but it may be possible to find a more specific solution, so
maybe we wouldn't need to compromise with a more expensive option.

I'll also take a look at the circuit boards of the video capture cards we
have at work, and see what they have. It may also be worth us studying some
of the other audio manufacturers' implementations, to see if there's a
particular trend, and why.

On Wed, Aug 17, 2011 at 12:07 PM, John Rigg <[hidden]> wrote:

> On Wed, Aug 17, 2011 at 12:41:00PM +0200, Jeroen Van den Keybus wrote:
> > What jitter performance would actually be required by pro-audio ?
>
> Putting hard numbers on this is difficult because jitter specs given
> by many converter and clock manufacturers are effectively meaningless
> due to insufficient information about how the figure was derived.
>
> There's an AES paper about this by Bruno Putzeys which should be required
> reading for anyone designing converter clocks IMO. A copy is available
> at the Grimm site:
> http://www.grimmaudio.com/whitepapers
> It's the "clock jitter spec.pdf".
>
> What would be acceptable for consumer audio wouldn't necessarily be
> good enough for pro audio. For example, many consumer grade interfaces
> use the raw clock output from an S/PDIF receiver chip like the CS8414
> as the converter clock source when syncing to an S/PDIF input. This is
> audibly inferior to a using decent crystal oscillator. For a pro work
> additional jitter reduction would be required to reduce the jitter to
> an acceptable level in this example.
>
> The holy grail for designers is a converter that sounds uniformly
> excellent whatever the clock sync source. Even some well known pro level
> converters fail in this regard.
>
> John
> 
> Jack-Devel mailing list
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> http://lists.jackaudio.org/listinfo.cgi/jack-devel-jackaudio.org
>

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