In article ,
Andy Evans wrote:
What I heard more clearly (or believe I heard if you prefer) was an
improvement in resolution of more highly modulated parts.

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.

--
*Hard work has a future payoff. Laziness pays off NOW.

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

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.

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

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'.

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

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.

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).

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

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).

--
John Phillips

Andy Evans wrote:

Following on from previous posts where I found that various damping materials
affected the sound of my Pioneer CDP used as transport only (I have an outboard
DAC), I've found the same with the CD-Rom I'm now using. I went over to the
CD-Rom because the build was more sturdy and there seemed to be a better sound
in it, which started to happen when I swapped the switch-mode power supply for
a normal toroid PSU. That's the story so far
Latest step was to bolt the CD-Rom down to a 10mm slab of aluminium 9.5" by
6.5". This after seeing the Flatfish which is exactly that. It's sitting on the
carpet as I write - haven't tried any fancy feet yet!
Well, the sound is very noticeably clearer. A CD-Rom vibrates quite a bit in
your hand, so I guess this is dampening it usefully. The most noticeable thing
is that louder passages are less congested and shouty - they have soothed out
audibly.
Now I have no idea why resonances affect CD transports, but this is without any
doubt what I'm hearing - change the damping, change the sound. I suppose this
is back to the debate whether 'bits are bits' or whether the signal is complex
and affected by other factors.
Since it isn't hard to try, maybe somebody else would like to replicate bolting
a CD-rom down to a 10mm slab of alu? I wonder if the measurements would be
different on any parameters. Andy

Unless you are using the analogue outs, there is no possible reason why the sound (
digital data ) should be remotely in the least interested in your choice of power
supply, chassis or whatever. If there is gross damage to / contamination of the
media ( or maybe excessive vibration ) the error-correction will kick in ( CDs have
a *lot* of inbuilt error correction bits of data ).


You might as well suggest that in a PC - you can write better prose by using these
techniques - the 'interference' of the switching PSU etc - interfering with your
writing skills !


Graham

Andy Evans wrote:

No doubt these will be available soon from all good snake oil outlets.

We're talking engineering here - Fays metals, Chiswick. The difference is quite
audible, as I said, so I'm interested in knowing how resonance dampening
affects CD transports. Andy.

It doesn't ! CD transports are designed to tolerate such stuff ( vibration et al ).
How on earth do you think one can work in a car otherwise ?


Graham

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. So far I've had no
explanation. I don't mind if this is outside the subjective technical knowledge
of posters - our knowledge always has its limits.

Are you a troll or a clot ?

Digital data can't in any event be 'sweetened'. The zeroes and ones are either
there or they aren't. A CD mechanism can only read the data on the disc - it can't
change it - as you seem to be suggesting. A CD 'sounds' the way it is - period.
Clearly - converter accuracy will affect the final result ( that's analogue
circuitery ) - but the digital part is either there or it isn't.

Maybe you are experiencing 'error correction' on a poor quality / cheap mechanism ?
That *might* disturb the digital data, but has zero to do with type of power supply
or large lumps of metal.


Graham

"Ian Molton" wrote in message
...
Rob wrote:

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.

Ok, I'll bite.

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

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.

I've even done it whilst playing loud music too.

Will that suffice?

Well, it's one test but even it adds support to the 'vibration matters'
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'. I can think of tempertaure, media - I don't know, gravity,
magnetism, radiation! 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'.

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

Just one thing - would your test show jitter?

Rob

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 ?

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.


Graham

Andy Evans wrote:

I could tell you how to easily do a representative set of measurements(AK)

But evidently you can't explain an obviously audible phenomenon.

Audible to only you matey !

Clowns like you are two a penny. You *admit* you know nothing about digital
data methods and then try and tell us you know more about the stuff sounds !


Graham