In article , Don Pearce
wrote:
On Fri, 14 Jan 2011 17:13:42 +0000 (GMT), Jim Lesurf
wrote:

In article , Don Pearce
wrote:
On Fri, 14 Jan 2011 09:57:44 -0500, "Arny Krueger"

No, this simply isn't so. Matching a cable properly results in a flat
frequency response and a flat group delay. This reshapes the signal
perfectly.

Not if the cable loss changes with frequency. You can optimise by
playing with the matching, but not necessarily get a perfect output.

Over the kinds of frequency we are dealing with in audio, cables are
sensibly flat regards loss.

However I was picking up your unqualified statement that mathcing would
give a 'perfect output'. I agree the departure from perfection should not
normally be an *audible* problem. Indeed, if peoplw want to worry about
they should worry about the LF cable impedance departing from the nominal
value at high freqencies. :-)

Sure there will still be errors, but of minuscule magnitude. I don't
think I've ever seen a cable that wasn't good for hundreds of MHz if
used properly.

What spdif cable bandwidth is required for, say 100 ps of jitter with the
J-test? I'm curious about this as I'm wondering about transferring
192k/24bit as well as ye olde 44.1k/16bit.

As I'm currently looking at some DACs I've noticed statements that optical
spdif is limited to 48k. That isn't coax of course, but it made me wonder
where this stated limit is coming from, or even if it is true. That in turn
makes me wonder about jitter and transfer bandwidth/dispersion when people
are using higher sample rates, etc, than the now-traditional CD standard.

Slainte,

Jim

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