Hi Chris,
I have to agree with Rick.
I assume you agree with me that the quality of the analog signal depends on the
ATRAC decoder, the DAC and the analog stage.
I can come up with theories that explains why disc A sounds better than disc
B. But then again, this theory only applies to a unit that has the same clock
and the same power-supply for the entire unit. Ie, when you use a external DAC,
the theory doesn't apply.
There are a few things that could cause some sort of interference. Interference
that could get audible in the Analog stage. Most of these things are due to bad
design of the unit, but not the disc.
1) A disc that produces errors will activate some error correction algorithm.
Therefore it is possible that the ATRAC chip draws more power. Thus less
power for the analog stage. This will certainly degrade the sound. But in
what extend? I'm sure the only way to find out is to actually mesure
signals in the analog stage with the same data on several types of discs.
Note that the JA20ES has seperated power-supplies for the digital and the
analog stage. Thus this theory doesn't apply to your setup!
2) Each disc has the so-called "wide-groove sputtered magneto-optical recording
layer. The wide groove is wobbled by a 22.05kHz carrier modulated by the
address data. This type of pre-groove modulation helps the drive system to
control not only the tracking servo, but also supports the constant linear
velocity (CLV) control and access control during record mode." (Copied from
'The Rewritable Minidisc System' document found on the community pages.)
I can imagine that this carier could be used to produce the clock for the
whole digital system. Thus if this carier is not constant....
However, the 'read-ahead-for-6-seconds-standby-read-ahead...' that is
featured in EACH minidisc player, makes it impossible to use a clock derived
from this signal. Since a minidisc is read at 5x speed during a certain
amount of time ( enough to fill the 6 second buffer). It's than up to the
rest of the system to playback the buffer.
Ie, no matter how bad this wide-groove is implemented, due to the buffering
mechanism, there is no chance that the data on the disc is played back in
a not constant way.
Again the only thing that could influence the sound is the extra current
that will be used in order to track the disc if the wboling frequency isn't
constant.
Than again, it's impossible to hear this with a seperate DAC since it
doesn't use the same powersupply!
3) Vibrations in the disc can give tracking problems. Giving the same problems
with the analog stage as described before. Than again a DAC that has a
different power supply will solve all problems.
In howfar all of these theories can be prooven and mesured is unknown. Sony,
Sharp
and friends don't give us enough inside information to realy analyse the system
for faults. Thus it stays a theory. However, I've yet to see the first theory
that
holds up and explains why some discs sounds better than others.
Cheers,
Ralph -> was my answer to long?
[EMAIL PROTECTED] wrote:
>
> Hi Chris,
>
> Thanks for the note, and I hope you don't mind if I reply to
> MD-L, it's a topic that comes up every so often.
>
> "Chris Lloyd" <[EMAIL PROTECTED]> writes:
>
> > Being a seasoned minidisc and hi-fi user (in general), I feel that I
> > must write regarding the Minidisc Community Page position on the
> > 'minidisc blank' sound quality issue. Rather than rubbishing claims of
> > well (and some not quite so well) respected hi-fi magazines, why not do
> > your own investigations scientifically. I draw your attention to the
> > excellent article in Hi-fi Choice (October 1999) regarding minidisc
> > blanks. I believe that, although there is little (perhaps even no)
> > difference in the nature of the quality of data storage (and hence the
> > playback sound) due to the actual optical surface of the minidiscs in
> > question, in practise there is an audible difference in sound quality
> > between discs. It is the combination of the design of IC, be it Sony,
> > Sharp or whoever (and whatever quality of deck), that is at the heart of
> > the number crunching of every md recorder, and the quality of mechanism
> > that surrounds the disc that allows variations in tracking accuracy,
> > whilst recording, for any individual design of disc and, hence, allows
> > different levels of digital distortion to result on the disc (causing
> > variations in soundstage depth and other subtleties).
>
> > I know from experience that Sony ES mds sound far superior to TDK MJs,
> > ON A SONY JA20ES for example.
>
> Any search for differences would likely include:
>
> 1) good experimental work (serious double blind A/B/X type tests).
> 2) measurement of the error rate, after error correction.
> 3) a theoretical explanation for where differences might lie.
>
> I admit to not having done (1), but perhaps someone should try it.
> Even without doing (1), if (2) showed no differences after error
> correction (as my simple check of block error rates implied [see the
> FAQ, http://www.minidisc.org/minidisc_faq.html#mdquality]) there would
> seem to be no point in doing (1). But my main problem in any case is
> that I cannot imagine an explanation (3) that would hold up to any
> serious scrutiny.
>
> Yes, I have heard of differences being reported due to disc tracking
> problems causing noise in the analog stage of some [cheap] MD players.
> But this is not a problem with the discs so much as it is a problem
> with the playback units. If the experiment is repeated with an
> external DAC, the problem will not appear (this is presumably even
> admitted by the folks who conduct such experiments).
>
> If you want to pursue it further, please first give a plausible
> explanation for how certain discs can sound better. I find the claims
> that some discs have certain general characteristics (e.g. "better
> bass", "better top end") to be comletely at odds with how audio
> information is stored digitally and give them a summary dismissal.
>
> Regards,
> Rick
--
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"For many years, mankind lived just like the animals. And then
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We learned to talk."
-- Stephen Hawking, later used by Pink Floyd --
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