CD transports and resonance
 

In article , Pooh Bear
wrote:

mick wrote:

I read somewhere (sorry, can't give a ref) that the error correction
on transports intended for audio is more lax than on those intended
for data, as your ears are incapable of detecting low error rates but
are more sensitive to the gaps caused by error correction. If that is
so, then using a data drive for audio may give a different sound, but
not one that is necessarily "better" as it will contain a different
sort of inaccuracy! I'm sure someone will be able to correct me on
this if I'm wrong.

There's a lot of error correction capability on a CD. Hamming encoded
IIRC. Forget how many bits of error it can correct transparently.
Philips / Sony expected early CDs to have lots of errors so needed them
to be correctable.

Bear in mind that it was expected that early CDs would *need* error
correction. I'm sure they are much better now.

I can't recall if the CD standard includes 'error concealment'. Anyone
know ?

Nominally left to the player. The system will use the redundancy to correct
errors. Where the relevant correction data is inconsistent and this can't
be resolved interpolation may be employed. Details at the choice of the
player manufacturer.

The German broadcaster WDR ( IIRC) found that subjective differences
between *DAT* transports was due to head misalignment causing error
concealment to kick in. Some units suffered more than others. Error
*concealment* kicks in when there aren't enough valid bits to
transparently *correct*.

Error *concealment* is *not* audibly transparent.

I doubt that CDs are troubled by this though.

In general, I'd agree. But I have enountered some CDs where the error
levels produce obvious audible problems in some/all players. In my
experience this is rare, though.

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
 

In article , Andy Evans
wrote:
you will keep encountering effects which will seem like "mysteries of
science" until you put the required time and effort into tests and
evidence that would allow a systematic explanation. Without this info,
there is not much others can guess. (JL)

That's a completely reasonable point. I've already pointed out some real
world considerations, however. I do have a scope but I've never used it
yet, and I have a raft of things that will come before that as a matter
of urgency. For those without scopes - and there are a few on this ng -
reports of building experiments will be aural. That's a fact of life.

Not really. It is a choice that you (and some others) make.

My own choice is to develop and test using appropriate test gear and
diagnosis methods *as well as* listening. Also to base development on
trying to understand what is actually happening in terms of the physics and
engineering involved.

I'm afraid, though, that the situation remains that many such things may
well remain 'mysteries' to you until such time as you proceed in more
systematic manner in collecting relevant data. Until then, I'm afraid that
your asking for 'help' isn't useful when you then disregard what actual
help is offerred.

The 'help' I can offer is to explain how you can investigate. Your choice
to use this, or disregard it. But if you disregard it, then the resulting
lack of understanding stems from your choice, I'm afraid.


Now, commonly builders report on projects for many reasons: a) to get
help if things go wrong b) to report particular changes which appear to
be sonic improvements in case others want to consider or try them.This
may not be any more significant than "I heard this, don't really know
why" c) in motivational terms to get support and positive feedback from
fellow enthusiasts for several hours at the drill press and soldering
iron. This is completely reasonable.

It is completely reasonable for people to ask for advice and information.

However it is, in turn, completely reasonable for those who are invited to
assist to point out what may be required in order for progress to be made.

Without said info I can only speculate as to what *might* be occurring, but
without relevant evidence, we can't get beyond that point.

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
 

In article , Tat Chan
wrote:
Pooh Bear wrote:

There's a lot of error correction capability on a CD. Hamming encoded
IIRC. Forget how many bits of error it can correct transparently.
Philips / Sony expected early CDs to have lots of errors so needed
them to be correctable.


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

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
 

In article , Tat Chan
wrote:
Rob wrote:


Rob, getting the 'data off the disk' in a reliable manner is the only
thing that matters in this context. If the output stream of 1s and 0s
from an undamped and damped transport is exactly the same, then the
damping doesn't make a difference.

Slight quibble. The above assumes we can then convey the bitstream to the
DAC with no unintended spurious effects. The most well-publicised version
of this is 'jitter' in various forms.

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.

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
 

John Phillips wrote:
In article , Ian Molton wrote:

will you accept that two identical bitstreams will reproduce identically
through a given DAC?


It is not clear if this include timing as well as data. I assume both.
However, for the sake of clarity if the jitter on the bitstreams were
different and the DAC merely replicated the incoming clock on its D/A
converter there could be an audible difference.

Indeed, we've had a jitter thread before and the (predictable)
conclusions we

1) a good dac is (to all reasonable limits) immune to all but the worst
jitter
2) a source of even marginal quality will still have jitter far below
audible limits even on a poor DAC
3) full reclocking is the only way to fully reconstruct the signal
jitter free (to the limits of the reclocking units clock)

CD transports and resonance
 

Rob wrote:

Well, it's one test but even it adds support to the 'vibration matters'

Huh? Its a test in full-on-vibration conditions - have you ever heard a
CDROM spin a disc for 50x thats such a poor quality disc it keeps
slipping to 10x or less?

hypothesis it wouldn't necessarily explain what's happening. The hypothesis
(antithesis if you like) is that 'metal blocks strapped to CD ROMs affect
sound'.

It was suggested that 'metal blocks improve sound', actually. since not
using metal blocks results in perfect extraction, I dont think theres
any validity to the theory.

I can think of tempertaure, media - I don't know, gravity,
magnetism, radiation!

gravity?! are you suggesting the difference in gravitational field over
2 inches height of the player will even be detectable?! or did you mean
andy should drop the player?

radiation is also damn unlikely, given andy appears to still be alive
and cacner free...

I just have no idea. My problem with this is a
reaction to the absolute dogma of positivist approaches: 'if it measures,
it's real'.

Im certainly willing to accept a weird hypothesis, but if any wants some
credibility he will have to *at least* perform the most basic tests of
all - not techinical tests at all, but the psychological bare minimum to
establish the effect is real.

I have absoltely no technical understanding of the issue. I've read a few
articles and follow Jim Lesurf's contributions with interest. JL is probably
the most qualified to explain things from the
technical/quantitative/positivist viewpoints - and you will note his reply
in this context is slightly equivocal - there is 'wiggle room'

Indeed - Jim has graciously allowed andy to admit defeat by saying the
effect is due to noise from the player and nothing to do with digital
adio at all. I note Andy still hasnt bitten though...

- and, IIRC,
he is/has been a user of dedicated transports, although this may have been
to do with DACs, can't remember.

Actually hes said over and over that one of his players is using a
standard PC transport and sounds no different.

Just one thing - would your test show jitter?

No, it wouldnt, however if jitter was great enough to be audible then
either his DAC or transport, or both, would be broken.

CD transports and resonance
 

Tat Chan wrote:

Pooh Bear wrote:

There's a lot of error correction capability on a CD. Hamming encoded IIRC.
Forget how many bits of error it can correct transparently. Philips / Sony
expected early CDs to have lots of errors so needed them to be correctable.


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

Thanks for refreshing my memory on that point.


Graham ;-)

CD transports and resonance
 

In article ,
Dodge McRodgered wrote:
Even if that's the case, you accept that Andy "hears" what he says he
can hear?

No. All I'm prepared to accept is that he *thinks* he can hear a
difference. The other alternative doesn't bear thinking about. ;-)

--
*Not all men are annoying. Some are dead.

Dave Plowman London SW
To e-mail, change noise into sound.

CD transports and resonance
 

I think this has been a useful thread for raising some of the issues about
measurement and non measurement. Just to go over this ground again, we know
that this ng is used both by those with measuring equipment and those without.
At the moment I'm without - not by choice particularly, I just haven't made
time to learn how to use my scope. I'm far from against measurement, and indeed
I take my gear round, once finished, to a friends to have it measured by quite
sophisticated equipment. Anyway, the point I'm making is that there are those
on this ng without access to measuring equipment and they have as much right to
make comments about their systems using the measuring equipment they do have,
which is their ears. In return the engineers needing measured data are quite
entitled to dismiss the results as unproven. I have no difficulty with that.
But this is not the whole story. Let us now take the case of a person who makes
a statement on the ng "I hear phenomenon A". If the response is "If you don't
have mesurements to prove it I won't believe it", then that's fine. But that
frequently isn't the response. If the response is "If you can't measure it you
should not have made that statement". Since we know in advance that there are
those on the ng wthout measuring equipment, to imply that they should not have
made a statement without measured data would be effectively to gag them. They
have as much right to make observations as the next man, so I would regard
gagging ng members as wholly unacceptable, even elitist. And if in the same
post we have "the poster should abide by the Scientific Method" and "the poster
is an idiot", we know that posters are not idiots so we must further level the
charge of hypocrasy to add to elitism. To recap these points:
1) this ng is for those who measure with equipment and who measure with their
ears
2) anybody has the right to disbelieve anything
3) to imply that somebody without measuring equipment should not post opinions
that can't be measured is elitist
4) to simultaneously ask for scientific methods and make fundamental mistakes
in measuring the intelligence of others is hypoctitical.

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

CD transports and resonance
 

On 08 Nov 2004 09:20:43 GMT, ohawker (Andy
Evans) wrote:

I think this has been a useful thread for raising some of the issues about
measurement and non measurement. Just to go over this ground again, we know
that this ng is used both by those with measuring equipment and those without.
At the moment I'm without - not by choice particularly, I just haven't made
time to learn how to use my scope. I'm far from against measurement, and indeed
I take my gear round, once finished, to a friends to have it measured by quite
sophisticated equipment. Anyway, the point I'm making is that there are those
on this ng without access to measuring equipment and they have as much right to
make comments about their systems using the measuring equipment they do have,
which is their ears. In return the engineers needing measured data are quite
entitled to dismiss the results as unproven. I have no difficulty with that.
But this is not the whole story. Let us now take the case of a person who makes
a statement on the ng "I hear phenomenon A". If the response is "If you don't
have mesurements to prove it I won't believe it", then that's fine. But that
frequently isn't the response. If the response is "If you can't measure it you
should not have made that statement". Since we know in advance that there are
those on the ng wthout measuring equipment, to imply that they should not have
made a statement without measured data would be effectively to gag them. They
have as much right to make observations as the next man, so I would regard
gagging ng members as wholly unacceptable, even elitist. And if in the same
post we have "the poster should abide by the Scientific Method" and "the poster
is an idiot", we know that posters are not idiots so we must further level the
charge of hypocrasy to add to elitism. To recap these points:
1) this ng is for those who measure with equipment and who measure with their
ears
2) anybody has the right to disbelieve anything
3) to imply that somebody without measuring equipment should not post opinions
that can't be measured is elitist
4) to simultaneously ask for scientific methods and make fundamental mistakes
in measuring the intelligence of others is hypoctitical.

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

Andy, why do you misrepresent what we have been saying. Certainly in
respect to your resonance damping claims we have said precisely what
you say here - *use your ears*. This doesn't require any special
equipment whatever - all it needs is for you to listen to your
equipment, not look and listen. There is no hypocrisy here, and those
of us who are saying it are notably those who understand the balance
between measuring and listening, particularly the ways in which they
support each other in the design of hi fi equipment. If you are a
designer you do actually need both at all stages of the design
process. And it is the fact that we understand how various bits of the
system work, and what factors can have which effects that allows us to
dismiss so readily your claims regarding CD resonance.

When we ask you to do the real *listening* tests, it is not in
expectation that you will come back here with some wonderful new
scientific principle that we were unaware of, but in the hope that you
can move your understanding on a bit. Patronising? I hope you don't
see it that way.

So to answer your points as you raise them

1. Most emphatically no. Listen any way you like, and post whatever
opinions you like, but if you announce the discovery of some effect
that the rest of us believe to be impossible - be prepared to defend
it, not moan about being challenged.

2. Not sure what you mean by having the right. Believe or disbelieve
what you like - it is not a question of rights. But if you make an
assertion, be prepared to offer a defence of your position.

3. Post whatever opinions you like - nobody is worried. Post an
assertion that you have discovered a new effect, and you must be
prepared to defend your claim.

4. Just do what you know to be right. You have training in psychology,
and it shouldn't be necessary to explain this to you. Is it not fair
to call somebody who wilfully fails to follow a method he knows to be
the only one that yields a true result unintelligent?

d
Pearce Consulting
http://www.pearce.uk.com