13 Nov
2009
13 Nov
'09
7:53 p.m.
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.