[LAU] open hw soundcard (was Re: status usb2 for sound)

[fons at kokkinizita.net]

On Fri, Nov 13, 2009 at 11:21:47PM +0000, Folderol wrote:

> Looking up the AES spec quickly reveals 48kHz +/- 10ppm. If the
> card's master oscillator has that kind of stability, it would surely
> require only very tiny slow adjustments to keep two of them in sync.
> Worst case would be them consistently drifting the maximum allowance in
> opposite directions, which if my maths is up to scratch results in
> about a second before they would actually get out of step by 1 cycle.

And the PLL would be needed only for word-clock sync, so
it can be left out at the start.
 
> A quick google reveals 5ppm temp compensated oscillators with a a 7ppm
> voltage controlled pull-in - no idea how much these cost though.

When I was with Alcatel Space, canned of-the-shelf VCXOs 
were regarded as 'cheap' components. I guess they still
are unless you want some odd frequency. 

Apart from stability and tuning range, the parameter to
check is the phase noise spectrum. Most of these things
are designed for digital applications where is matters
less.

Ciao,

-- 
FA

Io lo dico sempre: l'Italia è troppo stretta e lunga.