DAB MP2 bitrate question
 

In article , David Looser
wrote:
"Serge Auckland" wrote in message
...


It's also rather interesting to see how much jitter is audible. It's
all very well to say digital is crap because of the jitter, but it
takes a huge amount of jitter before it's audible. As a reference, see

http://audiopages.googlepages.com/JitterAudibility.pdf

Considering that turntables and tape machines have hundreds of time
the jitter of CD players, nobody complains that they sound crap
because of the jitter. Maybe because it's called wow and flutter, and
that sound nice and analogue rather than nasty digital jitter.


The amount of jitter on the audio data entering the DAC of a CD player
is absolutely negligible, because of all the buffering that the data
goes through as it passes through the error checking/correcting system
etc.

It is worth bearing in mind that 'jitter' can come from a variety of forms
of engineering limitation. Examples include inherent phase noise on the
clocks, and the finite bandwidth and response time of the channel feeding
the DAC. All depends on design details. Note the 'data dependent' jitter
used for magazine measurements. But these points may be irrelevant in
practice since so far as I know, no-one has shown in controlled blind tests
that the levels of jitter that are typical can actually be heard. There are
of course, many assertions. But as in some other areas where audibility
claims are made, the 'evidence' generally seems to be on the basis that we
have to take the word of the person making the claim.

As I suggested earlier, the real point about jitter is whether it
produces problems with data recovery. If the jitter is so extreme that
it interferes with that process then there is a problem. In that case
no amount of buffering will make any difference. I'm not aware that CD
players have any particular problem in this area, though if anyone has
any hard evidence (as distinct from statements of the "sound cards
sound better than CD players" variety) I'd be interested to hear it.

Me also. :-)

Alas, there seems little sign that jamie will provide this. So I haven't
yet seen any reason to take his assertions seriously. Since he has
misunderstood and/or ignored the points I made there also seems little
point in trying to discuss this with him.

Given that jitter mechanisms might include things like rail noise, and
channel problems, it isn't clear to me why computer systems as a class
would inherently be superior, let alone audibly so. Although I am sure you
can justify many claims by defining one class as "good" and the other as
"not good" so preloading the claim to fit the selected classes - even if
one happened to be void of members. :-) One usenet debating ploys like
that do seem popular with those unable to employ the normal scientific and
engineering methods to obtain evidence.

Slainte,

Jim

--
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DAB MP2 bitrate question
 

Actually my mistake for not making this that clear!..

Jamie over on alt.radio.digital has asserted that most all CD digital
players sound ****e owing to all the jitter they have.

Has he published the details of how he did any level-matched blind
comparisons and how the stats of the results came out? Ditto for various
other details? Has he attempted to give a useful definition to "most all
digital players" beyond "those that would suit his assertion"? What fraction
of all the CD players in use has he tried, etc?

Doesn't seem so..

--
Tony Sayer