Posted by Matthew L. Martin on 11/10/06 12:36

G-squared wrote:
> Matthew L. Martin wrote:
> > Randy Yates wrote:
> > > Tom Stiller <tomstiller@comcast.net> writes:
> > >
> <snip 'guest'>
> >
> > > Actually, it can. I'll have to back-peddle a little here.
> > >
> > > S/PDIF is a single-wire interface that embeds the clock with the
> data.
> > > Because of this, problems with the interface that aren't serious
> > > enough to cause bit errors can still affect the sound by affecting
> the
> > > quality of the recovered clock. A PLL is used to recover the
> clock,
> > > and depending on the type of loop filter used in the PLL, input
> noise
> > > from cable degradations could introduce jitter into the digital
> clock
> > > and thus the reconstructed analog signal.
> > >
> > > How audible is it? That is a whole dissertation unto its own.
> >
> > According to test I did years ago when I had access to the proper
> > equipment the jitter induced sidebands on an impaired cable were
> 85dB
> > below the program material (CD test tones). One golden eared guy
> > duplicated my results with similar equipment, but he claimed he
> could
> > hear 85dB below the program material, so the jitter was audible to
> him.
> >
> > Matthew
>
> Matthew, on your jitter tests, did the hardware have the PLL clock
> recovery Stiller mentions ?

Of course.

> If so, was there any way to monitor the PLL
> error signal to see any relation to the jitter sideband issue ?

That is what the spectrum analyzer was for.

> Should
> we expect more recent hardware to behave better and if so, how much
> better in your estimation ?

Any design, new or old, that uses a large enough shift register to
buffer the incoming signal should have close to no jitter induced side
bands.

> Just curious and thanks

Note, "large enough" is pretty small.

Matthew

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You can't win
You can't break even
You can't get out of the game

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