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

Both are valid techniques, which I don't believe has ever been argued.

2) anybody has the right to disbelieve anything

Indeed so, and it would be instructive if more people raised their
disbelief thresholds! :-)

3) to imply that somebody without measuring equipment should not post opinions
that can't be measured is elitist

I don't recall anyone having posted any such suggestion.

4) to simultaneously ask for scientific methods and make fundamental mistakes
in measuring the intelligence of others is hypoctitical.

That would be 'hypocritical'................... :-)

But again, I don't recall anyone having posted any such suggestion.


So, let's cut to the chase:

Despite much whining and strawman-building by their opponents, the
'engineers' do *not* demand 'measurements', they simply request that
anyone making claims which fly in the face of 'common knowledge',
provide some *proof* of those extraordinary claims. This need not
involve *any* measurements in many cases, and in others will only
involve a simple voltmeter to equalise levels in a *listening* test.

Please note that the 'objectivists' in actual fact always ask for
*listening* tests, i.e. not objective tests at all, just subjective
test which are controlled to eliminate bias problems which
psychologists have known about for more than half a century. Bottom
line, the 'objectivists' are the ones who are asking people to
*really* trust their ears. We remain surprised that the
'subjectivists' steadfastly refuse to do this. Why do they so refuse?

In the context of this particular thread, it's certainly been
suggested that technology be employed to compare digital files
produced by the transport under various conditions, but that's because
the output of a CD transport is *entirely* definable by examination of
its digital datastream, given a competent jitter-crushing DAC.
--

Stewart Pinkerton | Music is Art - Audio is Engineering

CD transports and resonance
 

Stewart Pinkerton wrote:

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


Jim Lesurf wrote:



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! :-_

All that work to correct burst errors (CIRC) and ensure that the bits
can be read off the disc in a practical way (EFM), eh?

I suppose the mathematicians laid the foundation to ensure the data on
the disc would be self-correcting (up to a certain number of bits) and
the engineers found a practical way of getting the data off the disc in
real time!

;)

CD transports and resonance
 

Jim Lesurf wrote:
In article , Ian Molton
wrote:

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"... :-)

Again though, the CD is read as fast as required to keep the read-buffer
half full, which is, in turn drained at a constant rate. I cant see how
jitter filling that buffer could manifest on the output unless it was
great enough to drain the buffer or cause a read error that wasnt
correctable, neither of which would really be 'normal operating
conditions'...

CD transports and resonance
 

In article ,
Paul Dormer wrote:
A well worn disc is also likely to produce higher error rates
(naturally).

Wear suggests something which occurs normally with use - as happens with
an LP. CDs don't appear to wear as such - my very first one ever still
plays as new.

Damage would be a better term.

--
*No radio - Already stolen.

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

CD transports and resonance
 

"Ian Molton" wrote in message


Again though, the CD is read as fast as required to keep the
read-buffer half full, which is, in turn drained at a constant rate.
I cant see how jitter filling that buffer could manifest on the
output unless it was great enough to drain the buffer or cause a read
error that wasnt correctable, neither of which would really be
'normal operating conditions'...

You've got things right. The buffered read technique used by *every* optical
disc transport is in essence, a massive anti-jitter box. The jitter of the
digital data stream coming out of an optical disc transport is set by the
output clock, not mechanical vibration in the transport.

I've done experiements in which I measured the jitter coming out of a CD
player suspended a few inches above a large woofer playing various
frequencies at loud levels. The jitter showed no increase right up to the
point where mistracking started.

CD transports and resonance
 

"Kurt Hamster" wrote in message

On Sat, 06 Nov 2004 09:57:26 +0000 (GMT), Dave Plowman (News) used
to say...

In article ,
Andy Evans wrote:
But evidently you can't explain an obviously audible phenomenon.

Trouble is, Andy, most of your posts concern 'audible phenomenon'
that only you can hear...

If only one person can hear it then by definition it's audible is it
not?

Since sighted evaluations are being used, it is unclear whether or not
hearing is even involved.

CD transports and resonance
 

In article ,
Paul Dormer wrote:
Wear suggests something which occurs normally with use - as happens with
an LP. CDs don't appear to wear as such - my very first one ever still
plays as new.

Damage would be a better term.

Well I did say "well worn", by which I meant to infer scratched or
grazed, but OK I accept your correction..

Does a properly setup turntable actually cause audible wear with each
and every use?? I've never owned a high end turntable long enough to
know.

I'd say anything in mechanical contact must wear. My LPs certainly have.
;-)

I do have a few elderly CD's which have gained pinholes in the
metal layer just sitting on the shelf.. :-(

I've heard of this but not experienced it.

--
*Why don't you ever see the headline "Psychic Wins Lottery"?

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

CD transports and resonance
 

In article ,
Kurt Hamster wrote:
But evidently you can't explain an obviously audible phenomenon.

Trouble is, Andy, most of your posts concern 'audible phenomenon' that
only you can hear...

If only one person can hear it then by definition it's audible is it
not?

To some, yes. Are the voices still troubling you?

--
*How can I miss you if you won't go away?

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

CD transports and resonance
 

In article ,
Paul Dormer wrote:
A legendary Nimbus rot job..

Didn't Nimbus develop their own manufacturing facility - much to the
amazement of the majors? Considering how difficult this must have been a
few flaws aren't surprising.

--
*Sorry, I don't date outside my species.

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

CD transports and resonance
 

"Paul Dormer" wrote in message


For sake of argument, wouldn't it be quicker and more fun for Andy to
just make whatever changes he feels improves his CD drive to his ears,
and get on with his life rather than conducting a series of boring
tests?? ;-) I mean.. permutations of stabilization technique could be
very long winded. Eg, try some feet under it.. does it sound better?
Yes/No... OK let's move on...

Not scientific but less tedious... :-)

A great opportunity for Andy to intellectually spin his wheels. Show him
how, Paul its what you're good at.