CD transports and resonance
 

On 06 Nov 2004 22:57:54 GMT, ohawker (Andy
Evans) wrote:

I enclose what appears to be other people saying similar things. I am not
saying any of these opinions are causally linked to the same phenomenon, and I
have no way of knowing what they heard or didn't hear, so this is purely for
information. (Audio Asylum search)

All you are quoting are equally spurious claims and suppositions, with
not *one* single example of someone who has actually tried comparing
two output files from treated and untreated transports.


--

Stewart Pinkerton | Music is Art - Audio is Engineering

CD transports and resonance
 

On 07 Nov 2004 00:06:08 GMT, ohawker (Andy
Evans) wrote:

Given the time taken in fitting the plate this could easily be explained
by listening at a higher level or the ambient noise being lower. Or the
coffee or alcohol kicking in. There are so many variables with a time
lapse both in circumstances and your hearing that I'm surprised you can't
see this.

All the above are, indeed, factors that you would want to ask about. I don't
drink more than occasionally and never to excess, and I drink decaff so that
rules them out, but you're absolutely quite right to ask. I didn't change the
level at all, but ambient noise in London is always present. Another factor I'd
suggest is tweeter/ear height - if you get up and sit down, you're unlikely to
be in the exact same listening position, particularly since in my case the
front panel of the speakers is 6'6" from my ears. The difference in ear
position could be 2 to 4" I guess, even sitting in the same place, which would
have an effect on the sound. These questions are certainly relevant, and much
more constructive than saying 'it's all in your head'.


What would be constructive would be to rip files to hard disc and
compare them, for loud/quiet and damped/undamped. Until you do this
and find a difference, the overwhelming probability is that it *is*
all in your head. Any properly trained psychologist would choose this
as the most likely answer, before chasing arcane 'resonances'.

--

Stewart Pinkerton | Music is Art - Audio is Engineering

CD transports and resonance
 

On Sun, 07 Nov 2004 06:51:16 +0000, Dodge McRodgered
wrote:

"Dave Plowman (News)" emitted :

there's no assurance that there is in fact an audible phenomenon.

Apart from the fact that I can hear it.

I'm afraid that's only a 'fact' to you. To be certain it's not just your
imagination requires proper testing.

Fooling oneself that a 'tweak' produces an audible improvement is as old
as tweaks themselves.

Even if that's the case, you accept that Andy "hears" what he says he
can hear?

Is that what the voices tell you? :-)
--

Stewart Pinkerton | Music is Art - Audio is Engineering

CD transports and resonance
 

On 07 Nov 2004 09:52:31 GMT, ohawker (Andy
Evans) wrote:

Jim says: "we have no assurance that your descriptions are a reliable guide
to what actually may be occurring."

That's entirely correct. Andy


So please, Andy. Go and establish that the effect you describe is one
with physical substance, and is not a simply a psychologic delusion,
then come back here and report whether we do, or do not have something
worth discussing.

Use your knowledge and experience in psychological testing in
establishing the facts. Describe to us your protocol so that we can
agree the validity of the procedure.

If in the face of all this, the phenomenon persists, you can still
discern the difference, then you have something to present. At the
moment you have nothing.

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

CD transports and resonance
 

In article , Andy Evans
wrote:
All it takes is for somebody independent to change between two sources
in a random fashion.(snip).. the minimum you would do before even
considering reporting to the world.

Hello Don - now, are you seriously suggesting that I buy another
identical transport (which is an obsolete model), set up a switching
device and go out of my way to get a third party to operate it just in
order to make an observation to a recreational newsgroup?

I had thought you were asking for advice and information on the possible
cause of what you beleive you hear, and by implication, how it could best
be dealt with. To do this, you require suitable evidence you can give to
others.


Some parties on this newsgroups seem to think that before stating
anything you should set up a complex DBT which would probably take
several days of one's time and require a variety of equipment and third
parties. Now if I were saying "I have discovered something new, I'm
confident that I'm the first to discover it and I'll be applying for a
patent this week and sending my findings to three scientific journals
once validation is complete" - then, and only then, would I consider
that such demands for DBTs etc had any place on a recreational
newsgroup. Andy

Not really a question of "discovering something new" but of testing if you
have discovered anything at all, and if so, what.

Slainte,

jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
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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:
Bolting a plate to the case is likely to alter the resonance of *that
case*. Why should that make a difference to the drive or electronics?
(DP)

Hello Dave - that's exactly the question I'm asking.

To find an answer, you have to perform the relevent tests, and collect the
data which you can then use as a basis for understanding. Your choice if
you wish to do this or not. I, and others, have suggested some test methods
that seem relevant. Up to you to choose to employ them or not. However if
you can't be bothered, then why ask for help?

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
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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 , John Phillips
wrote:
In article , Ian Molton wrote:

There may be some quirks to consider here too.

AIUI, a few years ago only CD-ROM transports used to have three-beam
lasers (as opposed to CD-DA transports with a single beam) and were
reported to have rather lower first-stage soft read error rates due to
better tracking of the CD.

My understanding is that the Philips mechanisms for CD-A started off with
single beam dither tracking, but the Sony ones started as three-beam. I
think this continued for many years, but am less sure of that.

So, maybe there is a hypothesis to test here concerning the error
performance of the CD transport.

This may well have been behind Meridian's use of CD-ROM transports in
their CD players years ago when others were still using CD-DA
transports. This seems to have changed over the last few years as many
audio CD players have come to use three-beam transports too.

My understanding is that they stayed with the transports they were familiar
with as they'd put a lot of work into developing their own in-house servo
control software, etc. So far as I know, the main distinction, though was
not between dither tracking and 3-beam, but between x1 and xN with
re-reads.

However, for low enough raw error rates (hard plus soft) this should all
get corrected anyway (although, again, CD-DA format error correction is
not as good as CD-ROM format error correction). My experience
recovering the data from physically damanged audio CDs is the same as
Ian M's: until a CD is really bad, multiple extractions on a three-beam
CD-ROM transport produce completely identical bitstreams (I'm not
including timing here).

My experience is the same as the above.

I have not followed the thread well enough to recall just what CD
transport was being used for Andy's initial observation but it is
certainly my observation that some transports are audibly worse than
others with damaged CDs. I can demonstrate that with the three current
transports I have (four including the car player).

My experience is similar. Indeed, I have had some faulty discs which
produced quite obvious clicks/pops/swishes in one player but not another.
This included players like the Quad 67 and the Meridian 200/263.

However I can also demonstrate to myself that the additional vibration
isolation I have tried (not the same thing as Andy tried) on my main CD
player - a three-beam transport - makes no audible difference for all
CDs I have tested (including the damaged ones).

My experience is the same as the above. I *have* felt that damping can
help, but for reasons that do not have anything to do with the actual
digital output of the transport.

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
 

On Sun, 07 Nov 2004 09:27:06 +0000, 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 ?

It does. Uncorrected errors may be concealed, i.e. the system takes a
'best guess' at what the missing sample(s) should have been, or
unconcealed 'mute' errors where the output is silenced - usually for
less than a millisecond. The general consensus is that with a standard
commercial CD you get one sub-millisecond concealed error about once
every five minutes, and somewhat less than one 'mute' error per disc.
Anyone here think that either of those will be audible? Otherwise, the
datastream is *perfect*.
--

Stewart Pinkerton | Music is Art - Audio is Engineering

CD transports and resonance
 

On Sun, 07 Nov 2004 21:07:43 +1100, Tat Chan
wrote:

Rob wrote:

"Stewart Pinkerton" wrote in message
...

Exactly! Just rip files from that transport in the four sensible
conditions - music on and off, large 'damping' mass attached and not
attached. Check to see if the files differ. If they do, investigate.
If they don't, forget it.

No no no SP! Try it my way, in a measured manner. Or, is the
'data-on-the-disk' the *only* thing that matters in this context?

Sure it is - what else would possibly matter in a device which outputs
a digital datastream? That's what makes this such an easy thing to
verify!

If it is,
you've run out of avenues and reached the sides of your box.

It's a box which has been well defined for twenty years - as has
auditory hallucination and expectation effects, which Andy *should*
know about, but is conveniently ignoring. Shrink, shrink thyself!
Also, Andy is reporting audio-related effects from a device which
outputs a coded datastream which is not in any direct way related to
the final audio signal.

No problem with
that. Just say, sorry Andy, I don't know.

(Having said this, the data might be different!)

Indeed it might, but this would indicate a seriously underperforming
transport.

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.

Quite so, also if it is not affected by acoustic feedback from loud
music playing. Heck, put the damn thing right in front of the speakers
if you like!
--

Stewart Pinkerton | Music is Art - Audio is Engineering

CD transports and resonance
 

In article , Rob
wrote:


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

Dunno about that. My views should be treated as being as potentially
fallible, just like anyone else's. :-)


- and you will note his reply in this context is slightly equivocal -
there is 'wiggle room' - and, IIRC, he is/has been a user of dedicated
transports, although this may have been to do with DACs, can't remember.

There are some 'potential' problems with data recovery, jitter, etc.
However:

1) They should not really matter in decent players, with decent discs, etc.

2) Can't reliably assess anything about Andy's reports without relevant
data.

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