CD transports and resonance
 

Jim Lesurf wrote:

In principle this should not be a problem. In practice it probably is not a
problem for most systems/disc. But it *might* be a problem in some cases
where the player/disc/DAC arrangement is unusually poor for some reason.

surely (massive) jitter from the *disc* end of things would manifest as
read errors rather than jitter in the output stream?

CD transports and resonance
 

I'm talking about listening in an environment where tester bias is not a
factor. (DP)

That's a fair point.

=== Andy Evans ===
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CD transports and resonance
 

I think the question here is what constitutes a measurement. If you
have hung a scope on an output, you have made a measurement. If you
have made a double blind, level matched test between two items, and
found a significant (chi squared) difference, then you have made a
measurement every bit as valid as the first.

Again, a fair point.

=== Andy Evans ===
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Audio, music and health pages and interesting links.

CD transports and resonance
 

you don't need any particularly specialised equipment to do comparison testing
at its most basic level. All that's needed really is
not to have sight of what the combination is you're testing. After all, if the
'improvement' really is there, it will disappear after the 'tweak' is reversed,
and re-appear when it's reinstated

This is what Don is saying, and I think it's entirely reasonable. Clearly I
could do this with some third party, so I accept that I have been "wilfully
negligent" purely in listening (without going into the question of measuring
equipment). I'm not sure what third party I can press gang into this - I have
nobody handy, but it's a reasonable point that listening tests can be done much
better than I did.

=== Andy Evans ===
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Audio, music and health pages and interesting links.

CD transports and resonance
 

"Andy Evans" wrote in message

CD transports are designed to tolerate such stuff ( vibration et al
). How on earth do you think one can work in a car otherwise ?

Hello there - I never said it didn't work - that's not the issue.
Also the changes are subtle, and not something you'd have a hope in
hell of hearing in a car. As I've constantly said, this is quite
paradoxical.

No, it's imaginary.

I suppose you are enjoying all the attention you are getting, Andy.

CD transports and resonance
 

In article , Tat Chan
wrote:
Jim Lesurf wrote:
In article , Tat Chan
wrote:



Actually, CD uses a form of the Reed Solomon code. Though the Hamming
code would provide error correction as well.



Not sure of all the details, but yes IIRC it is a form of cross
interleaved RS code. I think this is a 'block' code equivalent to a
hamming code.

I haven't done this in a while, but IIRC the Reed Solomon code is a type
of BCH code, which itself is a cyclic code.

I'm struggling to recall the details as it is ages since I read the info.
However I think the above is correct. Also, the data is processed via 'EFM'
(8 to 4 modulation). This essentially adds 6 extra bits of redundancy to
each 8bit byte of data. Thus redundancy (for error correction) is added at
more than one level in the process.


However the channel bit stream is encoded on a number of levels
between the sample data and the disc.


did you mean 'cross interleaved code' when you said 'encoded on a number
of levels between the sample data and the disc'?

Not quite. The interleaving and RS is one 'layer' of this. The interleaving
being to make that level's redundancy be for different sets of 'bits' than
the EFM additional bits. The process involves at least 2 or 3 'levels' of
re-encoding or re-arranging of the data. The details are in the relevant
Philips papers (and some in my textbook on this) but I can't recall all the
details!

Slainte,

Jim

--
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Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

CD transports and resonance
 

In article , Ian Molton
wrote:
Jim Lesurf wrote:

In principle this should not be a problem. In practice it probably is
not a problem for most systems/disc. But it *might* be a problem in
some cases where the player/disc/DAC arrangement is unusually poor for
some reason.

surely (massive) jitter from the *disc* end of things would manifest as
read errors rather than jitter in the output stream?


The usual academic response. "Depends what you mean by..." :-)

Jitter when trying to read the channel bit steam off the disc might mean
some bits were lost or repeated.

However (in principle) the player might accomodate that, but in doing so
end up jittering the 'correct' bit series it outputs so much as to annoy or
confuse a following DAC/receiver.

So "yes or no"... :-)

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

CD transports and resonance
 

"Don Pearce" wrote in message


Andy surprises me rather with his claims because he is fairly uniquely
positioned in his psychological training to understand the reasoning
and processes, yet chooses to ignore all his training and experience.

IME its not unusual to find people with psychological training who seem to
be completely oblivious to the need for well-designed subjective testing of
audio gear. Bruce Richman over in RAO seems to be one such person, and
Michael M. Gindi of the late unlamented FI magazine would be naother.

CD transports and resonance
 

I'd particularly like to thank Jim, Don and Dave Plowman for their
contributions to this thread - they have been helpful, patient and
constructive, and I've certainly learned quite a lot about the whole theory and
practice of measurement in the contentious area of what we call 'audio'. Andy

=== Andy Evans ===
Visit our Website:- http://www.artsandmedia.com
Audio, music and health pages and interesting links.

CD transports and resonance
 

On Mon, 08 Nov 2004 21:30:27 +1100, Tat Chan
wrote:

Jim Lesurf wrote:
In article , Tat Chan
wrote:

Actually, CD uses a form of the Reed Solomon code. Though the Hamming
code would provide error correction as well.

Not sure of all the details, but yes IIRC it is a form of cross interleaved
RS code. I think this is a 'block' code equivalent to a hamming code.

I haven't done this in a while, but IIRC the Reed Solomon code is a type of BCH
code, which itself is a cyclic code.

However the channel bit stream is encoded on a number of levels between the
sample data and the disc.

did you mean 'cross interleaved code' when you said 'encoded on a number of
levels between the sample data and the disc'?

It's a cross-interleaved Reed-Solomon (CIRC) code, using eight to
fourteen (EFM) modulation. Pick your preferred alphabet soup! :-_
--

Stewart Pinkerton | Music is Art - Audio is Engineering