26 Jan
2013
26 Jan
'13
6:09 p.m.
On Sat, January 26, 2013 4:52 am, Fons Adriaensen wrote:
Word clock only at 48 kHz seems to be a limitation of
some particular
equipment. It's not clear to me why things should be that way, I can't
see a good technical reason for it.
Maybe, it has to do with the boxes I was looking at being ADAT boxes.
I don't think there is a 'standard
practice' for audio clock distribution,
it will very much depend on the nature of the installation. If there's
anything video in house as well the primary source is likely to be video,
with audio derived from it. I a large facility with many studios the
system will be layered - a GPS driven master with an atomic standard as
backup driving a second level master generator in each studio. In such
a case the signal between the primary and secondaries could be video or
just 1, 5, or 10 MHz if no video sync is needed.
So with video master the audio clock would be derived from the colour
sub-carrier then? (horizontal seems kinda low) It seems odd that for a
non-video source an even ten based frequency would be used rather than
something like 1.536M for example, that divides evenly.
A few years ago that could have made sense as there
were few MADI routers.
But e.g. <http://www.directout.eu/en/products/m.1k2.html> will allow per
channel routing between 16 MADI ins and outs. Of course a wall of AES3
connectors looks cool... In practice the choice may be driven by any
existing wiring and in-house standards if e.g. a studio is upgraded.
1024 channels of routing seems like more than anyone could need, but I
remember terminating a wall full of audio lines at one of my first jobs in
a small town radio station, so I am sure there are places with more than
one of these boxes.
Probably yes, AES3 (known as AES/EBU here) surely is
free. AES 3 allows
unbalanced connections using coax and BNC, this may be a good option for
installations that have existing video wiring. But if the connector is
XLR the signal MUST be transformer balanced.
So AES10 (MADI) should be just as free? Or am I missing something? I know
there is a charge for the documentation for both AES 3 and AES 10, but is
there a use fee as well?
--
Len Ovens
www.OvenWerks.net