CD transports and resonance
 

"Stewart Pinkerton" wrote in message
...
On Sat, 6 Nov 2004 19:42:58 -0000, "Rob"
wrote:


"Stewart Pinkerton" wrote in message
. ..
On 06 Nov 2004 11:27:16 GMT, ohawker (Andy
Evans) wrote:

I have no wish to 'endow' (DP) anything. I'm reporting less distortion
in
highly modulated passages when a transport is damped.

No, you're reporting that you *think* something is happening. You have
as yet shown no indication that anything *real* is occuring.
--

If I were Andy I'd be feeling like someone asked to prove, for ever,
evidence of something that doesn't exist in the empirical world. Andy
can't
prove what he hears, and I'm inclined to think he (of all people) is aware
of placebo-type effects. Why can't you turn this round - instead of asking
him to prove it, you disprove it.

Why? Because common sense and engineering knowledge suggests that
there is no physical effect occuring. Hence, it's up to the person
making the extraordinary claim to provide proof of his claim. We've
seen the 'but I *heard* it!' claim far too often for things like
cables, to simply accept it on faith.

Simple hypothesis - test it and see what
happens.

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? If it is,
you've run out of avenues and reached the sides of your box. No problem with
that. Just say, sorry Andy, I don't know.

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

Rob

CD transports and resonance
 

John Philips) Thank you John for an interesting post. In response to your
question, my CD-rom is a Creative 36X-mx. I don't know if it is single or three
beam - it's probably ten years old I think. Andy

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

CD transports and resonance
 

On Sat, 06 Nov 2004 20:13:49 +0000 (GMT), "Dave Plowman (News)"
wrote:

In article ,
Rob wrote:
Andy can't prove what he hears, and I'm inclined to think he (of all
people) is aware of placebo-type effects.

Yet is continually offering up for comments things he can 'hear' that
others wouldn't.

And thinks that SS amps somehow remove something from the music which
valve amps retain, while all available evidence shows that 'valve'
sound is simply *added* artifacts. Perhaps he doesn't like to apply
his working scientific rigour to his playtime pursuits............

--

Stewart Pinkerton | Music is Art - Audio is Engineering

CD transports and resonance
 

In article , Rob
wrote:

"Stewart Pinkerton" wrote in message
...
On 06 Nov 2004 11:27:16 GMT, ohawker (Andy
Evans) wrote:

I have no wish to 'endow' (DP) anything. I'm reporting less distortion
in highly modulated passages when a transport is damped.

No, you're reporting that you *think* something is happening. You have
as yet shown no indication that anything *real* is occuring. --

If I were Andy I'd be feeling like someone asked to prove, for ever,
evidence of something that doesn't exist in the empirical world. Andy
can't prove what he hears, and I'm inclined to think he (of all people)
is aware of placebo-type effects. Why can't you turn this round -
instead of asking him to prove it, you disprove it. Simple hypothesis -
test it and see what happens.

Alternatively, lets ask for some evidence that might help one way or the
others.

e.g.s

1) Perform the test Ian has suggested. Play the same CD twice, and read the
bitstream and compare the bit/sample patterns. If they are the same we can
then conclude that the player is reliably reading the actual data and
feeding it to the DAC as the same series of values in each case.

2) If the result of the above shows the same patterns in each case. Repeat
with a suitable CD-A that would show up dither as sidebands/intermod on the
replayed waveform. Collect two copies again, and compare. If they are the
same, we can then reasonably think that the CDROM is feeding the same data
in the same way to the DAC in each case.

Hence by carrying out the above tests we would be able to get some idea if
Andy's belief that he can hear a difference is supported by tests. If the
test do show a difference, then the results would aid us in suggesting a
solution. However if both tests show no changes that correlate with the
cause he is suggesting we can reasonably assume that he is mistaken in some
way.

I suspect that behind your rather abrupt manner and bluster is a
charitable soul trying to dissuade people from throwing time and money
at what you see to be a pointless grail. I can't prove it though ;-).

Can't speak for Stewart. My intention is to encourage/help people to
develop in a more systematic manner, based upon developing a more reliable
understanding of what is actually going on. Doing this by performing
relevant tests whose results can be used for this purpose.

The problem at the moment is that I/we can make *guesses* as to what might
be happening, but without relevant data these remain just guesswork.

The Scientific Method has been around for some time now. My recommendation
is to employ it for questions like this. Might help a bit... :-)

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 , Rob
wrote:

"Stewart Pinkerton" wrote in message
...
On 06 Nov 2004 15:15:40 GMT, ohawker (Andy
Evans) wrote:

To resolve, employ suitable measurements. Otherwise we (including you)
have no real idea if the effects you describe have anything to do
with the 'causes' you assume.

Hello Jim - I'm open minded - my assumption is that it's to do with
resonance, I suppose, but I've been very clear in saying I don't
understand how this happens. I'm not in a position to measure, so my
next step is to find others who have observed similar things and
others who can offer some kind of explanation based on their own
empirical knowledge. Andy

Actually, your assumption is that there *is* a real effect. --

No, I read that as a finding.

No, the 'finding' is that Andy thinks he hears a difference. This does not
mean that we have 'found' either that the effect is produced by
'resonance' or to the actual CD player. To establish that, more tests of a
systematic and controlled nature would be required.

The assumption - and I think it's not unreasonable - is that stabilising
a cd mechanism brings audible benefits.

As a vague and unspecific generalisation that is fine. However it does not
establish that this *is* the case in this specific instance. For that we
require suitable tests to obtain relevant evidence.

I would find that assumption reasonable, in the sense that it's worthy
of test, because of the massive engineering you see in some CDPs and
stated preferences for particular mechanisms. I have no idea why, btw,
but I'd be curious if I could be bothered.

Agreed.

FWIW as I've already pointed out earlier in this thread, I have also had
reason to find that applying samping to quite a decent transport caused
what I feel was a slight but audible improvement. However this was for
reasons quite different to those being assumed here! I also think it
possible that I was mistaken, being human.

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
 

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.

CD transports and resonance
 

Jim wrote: "The subjective 'discription' you give has no clear information
content for anyone who was not using your ears at the time, or who does not
already by some other means know exactly what you are talking about.This does
not mean that we can all be certain the difference is entirely
imaginary. Simply that we have no real way of telling much beyond noting
that you think you hear something.

That's entirely correct, and well put. We do know incontravertibly that I
fastened a 10mm slab of alu size 6.5" by 9.5" with four 3M bolts to the
underside of a Creative 36X-xm CD-Rom, sat down in what I took to be the same
listening position after the delay it took to bolt the slab on, and listened to
the same test tracks again. The rest, as you say, we don't know accurately.
Andy

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

CD transports and resonance
 

In article , Dave Plowman (News)
wrote:
In article , Rob
wrote:
The assumption - and I think it's not unreasonable - is that
stabilising a cd mechanism brings audible benefits.

It would do if a record player. They can suffer from all sorts of
vibration influenced effects.

But a CD player is surprisingly digital. Assuming that digital signal
can still be read it will work normally. If it is subjected to severe
vibration it will stop - or at least produce some alarming noises.
Nothing really in between.

In principle this is not quite correct. Vibration and other effects may
cause some data loss at the reading level. Most of this will be corrected
by the redundancy, etc. But there is a risk that occasional sample values
with be incorrect. In a decent player, with a decent disc, this should be
very rare. But in an unknown transport with dubious support it may become
more common.

In principle, a CDROM drive can repeatedly re-read, but even then,
something might go wrong.

The difficulty, though, is that without some reliable and relevant evidence
we have no way to know if this is happening in Andy's case. Thus given that
the CD system is designed to work OK when vibration, etc, *are* present at
some level, we can't take it as established that this is a cause in this
case.

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
 

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? If it is,
you've run out of avenues and reached the sides of your box. No problem with
that. Just say, sorry Andy, I don't know.

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

Rob


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.

CD transports and resonance
 

On 07 Nov 2004 03:04:58 GMT, 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.

Timing doesn't matter, if it's a competent DAC.

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.

This is solved by using a competent DAC, not messing with the already
competent transport.

Contrariwise, a good DAC (from an engineering POV anyway) will deal
properly with input jitter up to some level and have a D/A converter clock
whose jitter is independent. (Although the threshold of audibility of
jitter was still not well established the last time I looked - but this
might have changed as it was a long time ago).

Quite so.

Nevertheless there is a hypothesis which could be tested which could
explain Andy's observation.

Indeed so, but Andy seems uninterested in investigating the
probability that there is nothing to hear.

If so I can disprove andys theory by ripping a CD on my PC at 30ish
speed and comparing the bitstreams.

I've done this before, with some pretty manky CDs, and have successfully
extracted identical bitstreams on two consecutive runs.

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.

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.

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).

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).

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).

Andy does not however seem to be interested in such testing, so what
to do?

--

Stewart Pinkerton | Music is Art - Audio is Engineering