Jitter and CD-R

[Guest]

Archived from groups: rec.audio.high-end (More info?)

"Timothy A. Seufert" <tas@mindspring.com> wrote in message
news:<i6XEc.8236$MB3.1645@attbi_s04>...
> In article <3KhEc.126350$eu.114636@attbi_s02>,
> Stereophile_Editor@Compuserve.com (John Atkinson) wrote:
> > "Timothy A. Seufert" <tas@mindspring.com> wrote in message
> > news:<cbq7b701kqb@news3.newsguy.com>...
> > > So let me get this straight: you are arguing that errors in pit
> > > lengths resulting in jitter in the signal read from the disc has
> > > audible effects, even when there are no changes in data values?
> >
> > That is correct. While I wouldn't generalize the audible effect of
> > jitter as "blurs the sound representation and increases the
> > high-frequency noise," I had understood that it was generally
> > accepted that time-base errors in the data read from the disc can
> > result in measurable changes in the recovered analog signal.
>
> If and only if pit length / position errors cause a sufficiently high
> bit error rate in the raw datastream that there are errors in the
> recovered sample values after the C1 and C2 error correction algorithms
> do their work.
>
> In other words, as long as the bitstream delivered to the DAC is the
> same, the recovered analog signal is the same, within the limits of the
> DAC.

I wish that were the case. Stereophile has published quite a lot of work
showing, basically, that jitter propagates through a D/A system. It can be
low-pass filtered but not eliminated unless heroic measures are employed.

> Jitter in the clock used to write a disc cannot propagate to
> playback _as_jitter_, for the simple reason that playback uses an
> entirely independent clock source.

Again I wish that were the case. Yes, the data recovery clock controls the
retrieval of the bitstream from the disc and also controls the word-clock
timing of the DAC. But what may be perfect on paper may well not be in
practice. Time-base error can vary significantly on CDs -- check out some
discs with the Plextools software -- and some players do not eliminate it
as much as one might wish.

John Atkinson
Editor, Stereophile

 

[Guest]

Archived from groups: rec.audio.high-end (More info?)

John Atkinson <Stereophile_Editor@compuserve.com> wrote:
> "Timothy A. Seufert" <tas@mindspring.com> wrote in message
> news:<i6XEc.8236$MB3.1645@attbi_s04>...
> > In article <3KhEc.126350$eu.114636@attbi_s02>,
> > Stereophile_Editor@Compuserve.com (John Atkinson) wrote:
> > > "Timothy A. Seufert" <tas@mindspring.com> wrote in message
> > > news:<cbq7b701kqb@news3.newsguy.com>...
> > > > So let me get this straight: you are arguing that errors in pit
> > > > lengths resulting in jitter in the signal read from the disc has
> > > > audible effects, even when there are no changes in data values?
> > >
> > > That is correct. While I wouldn't generalize the audible effect of
> > > jitter as "blurs the sound representation and increases the
> > > high-frequency noise," I had understood that it was generally
> > > accepted that time-base errors in the data read from the disc can
> > > result in measurable changes in the recovered analog signal.
> >
> > If and only if pit length / position errors cause a sufficiently high
> > bit error rate in the raw datastream that there are errors in the
> > recovered sample values after the C1 and C2 error correction algorithms
> > do their work.
> >
> > In other words, as long as the bitstream delivered to the DAC is the
> > same, the recovered analog signal is the same, within the limits of the
> > DAC.
>
> I wish that were the case. Stereophile has published quite a lot of work
> showing, basically, that jitter propagates through a D/A system. It can be
> low-pass filtered but not eliminated unless heroic measures are employed.
>
> > Jitter in the clock used to write a disc cannot propagate to
> > playback _as_jitter_, for the simple reason that playback uses an
> > entirely independent clock source.
>
> Again I wish that were the case. Yes, the data recovery clock controls the
> retrieval of the bitstream from the disc and also controls the word-clock
> timing of the DAC. But what may be perfect on paper may well not be in
> practice. Time-base error can vary significantly on CDs -- check out some
> discs with the Plextools software -- and some players do not eliminate it
> as much as one might wish.

I note that Timothy was careful to mention *audible effects* up there, in
the post you originally replied to. Has Stereophile published results of
testing for *that*?

--

-S.
Why don't you just admit that you hate music and leave people alone. --
spiffy <thatsright@excite.co>

 

[Guest]

Archived from groups: rec.audio.high-end (More info?)

In article <cc299h01riu@news3.newsguy.com>,
Stereophile_Editor@Compuserve.com (John Atkinson) wrote:

> "Timothy A. Seufert" <tas@mindspring.com> wrote in message
> news:<i6XEc.8236$MB3.1645@attbi_s04>...
> > In article <3KhEc.126350$eu.114636@attbi_s02>,
> > Stereophile_Editor@Compuserve.com (John Atkinson) wrote:
> > > "Timothy A. Seufert" <tas@mindspring.com> wrote in message
> > > news:<cbq7b701kqb@news3.newsguy.com>...
> > > > So let me get this straight: you are arguing that errors in pit
> > > > lengths resulting in jitter in the signal read from the disc has
> > > > audible effects, even when there are no changes in data values?
> > >
> > > That is correct. While I wouldn't generalize the audible effect of
> > > jitter as "blurs the sound representation and increases the
> > > high-frequency noise," I had understood that it was generally
> > > accepted that time-base errors in the data read from the disc can
> > > result in measurable changes in the recovered analog signal.
> >
> > If and only if pit length / position errors cause a sufficiently high
> > bit error rate in the raw datastream that there are errors in the
> > recovered sample values after the C1 and C2 error correction algorithms
> > do their work.
> >
> > In other words, as long as the bitstream delivered to the DAC is the
> > same, the recovered analog signal is the same, within the limits of the
> > DAC.
>
> I wish that were the case. Stereophile has published quite a lot of work
> showing, basically, that jitter propagates through a D/A system. It can be
> low-pass filtered but not eliminated unless heroic measures are employed.

I'm afraid that I'm not inclined to give Stereophile articles much
credence when it comes to technical matters, having read many a howler
whenever said articles are brought to my attention. It's an
enterntainment magazine, not an engineering journal.

> > Jitter in the clock used to write a disc cannot propagate to
> > playback _as_jitter_, for the simple reason that playback uses an
> > entirely independent clock source.
>
> Again I wish that were the case. Yes, the data recovery clock controls the
> retrieval of the bitstream from the disc and also controls the word-clock
> timing of the DAC. But what may be perfect on paper may well not be in
> practice.

The practice is that there is an oscillator feeding the DAC clock input.
In order for your claim to be true, somehow random variations away from
ideal placement of pit/land transitions on the disc must affect that
oscillator's jitter. This strikes me as more than a little unlikely.

The only remotely plausible explanation for such an effect that I've
ever seen put forth is power supply noise, but there are problems with
that idea too. The biggest being, why should there be any more power
supply noise than normal? The number of CMOS switching events in the
digital section of the player should not be any higher on average. This
probably holds true even when there are extra bit errors to correct,
since correction is a decoding step which must be done regardless of
whether there are errors.

--
Tim

 

[Toni]

Archived from groups: rec.audio.high-end (More info?)

Hi all,

En John Atkinson va escriure en 2 Jul 2004 00:12:33 GMT:

>I wish that were the case. Stereophile has published quite a lot of work
>showing, basically, that jitter propagates through a D/A system. It can be
>low-pass filtered but not eliminated unless heroic measures are employed.

AFAIK, for jitter, you only need to read the CD into your laptop
computer and then play it through the optical out to your
amplifier. The stability of your PC clock with any medium quality
digital I/O card will be much greater than the direct read from
the rotating CD.

Toni

 

[Guest]

Archived from groups: rec.audio.high-end (More info?)

Stereophile_Editor@Compuserve.com (John Atkinson) wrote:

>"Timothy A. Seufert" <tas@mindspring.com> wrote in message
>news:<i6XEc.8236$MB3.1645@attbi_s04>...
>> In article <3KhEc.126350$eu.114636@attbi_s02>,
>> Stereophile_Editor@Compuserve.com (John Atkinson) wrote:
>> > "Timothy A. Seufert" <tas@mindspring.com> wrote in message
>> > news:<cbq7b701kqb@news3.newsguy.com>...
>> > > So let me get this straight: you are arguing that errors in pit
>> > > lengths resulting in jitter in the signal read from the disc has
>> > > audible effects, even when there are no changes in data values?
>> >
>> > That is correct. While I wouldn't generalize the audible effect of
>> > jitter as "blurs the sound representation and increases the
>> > high-frequency noise," I had understood that it was generally
>> > accepted that time-base errors in the data read from the disc can
>> > result in measurable changes in the recovered analog signal.
>>
>> If and only if pit length / position errors cause a sufficiently high
>> bit error rate in the raw datastream that there are errors in the
>> recovered sample values after the C1 and C2 error correction algorithms
>> do their work.
>>
>> In other words, as long as the bitstream delivered to the DAC is the
>> same, the recovered analog signal is the same, within the limits of the
>> DAC.
>
>I wish that were the case. Stereophile has published quite a lot of work
>showing, basically, that jitter propagates through a D/A system. It can be
>low-pass filtered but not eliminated unless heroic measures are employed.
>
>> Jitter in the clock used to write a disc cannot propagate to
>> playback _as_jitter_, for the simple reason that playback uses an
>> entirely independent clock source.
>
>Again I wish that were the case. Yes, the data recovery clock controls the
>retrieval of the bitstream from the disc and also controls the word-clock
>timing of the DAC. But what may be perfect on paper may well not be in
>practice. Time-base error can vary significantly on CDs -- check out some
>discs with the Plextools software -- and some players do not eliminate it
>as much as one might wish.
>
>John Atkinson
>Editor, Stereophile

What you say may well be true; I'll ask you if you have any bias-controlled
listening evidence that any of this will matter to a listener using his home
reference system? At anytime with any commercially available recordings?

 

[Guest]

Archived from groups: rec.audio.high-end (More info?)

Steven Sullivan <ssully@panix.com> wrote in message news:<FX3Fc.10987$7t3.2143@attbi_s51>...
> John Atkinson <Stereophile_Editor@compuserve.com> wrote:
> > "Timothy A. Seufert" <tas@mindspring.com> wrote in message
> > news:<i6XEc.8236$MB3.1645@attbi_s04>...
> > > Jitter in the clock used to write a disc cannot propagate to
> > > playback _as_jitter_, for the simple reason that playback uses
> > > an entirely independent clock source.
> >
> > Again I wish that were the case. Yes, the data recovery clock controls
> > the retrieval of the bitstream from the disc and also controls the
> > word-clock timing of the DAC. But what may be perfect on paper may well
> > not be in practice. Time-base error can vary significantly on
> > CDs -- check out some discs with the Plextools software -- and some
> > players do not eliminate it as much as one might wish.
>
> I note that Timothy was careful to mention *audible effects* up there,
> in the post you originally replied to.

I didn't address audibility, except that that if there are measurable
differences in the analog signal, there may well be audible
differences.
In this response I was specifically addressing his statement that:
> > > as long as the bitstream delivered to the DAC is the same, the
> > > recovered analog signal is the same, within the limits of the DAC.

Which is incorrect. There are measurable differences in the
reconstructed
analog signal from the same bitstream, that result from different
anounts and types of word-clock jitter. If they are measurable, they
may
well be audible. For example, I once was a subject in a single-blind
test
comparing the same data on CD and CD-R, where the CD-R sounded
different.

> Has Stereophile published results of testing for [audibility of jitter]?

No formal tests of audibility, but a lot of anecdotal evidence. A 1993
article on the subject will be accessible in the free on-line archives
at www.stereophile.com on Monday July 5.

John Atkinson
Editor, Stereophile

 

[chung]

Archived from groups: rec.audio.high-end (More info?)

John Atkinson wrote:
> "Chelvam" <chelvam@myjaring.net> wrote in message
> news:<x%gEc.173343$3x.86251@attbi_s54>...
>> "Timothy A. Seufert" <tas@mindspring.com> wrote in message
>> news:cbq7b701kqb@news3.newsguy.com...
>> > So let me get this straight: you are arguing that errors in pit
>> > lengths resulting in jitter in the signal read from the disc has
>> > audible effects, even when there are no changes in data values?
>>
>> Not me but OEM http/www.daisy-laser.com, they are pretty reputable in
>> audio industry, aren't they?
>
> As a subsidiary of Philips, I guess they are "pretty reputable." BTW,
> if you have a Plexstor Professional CD-R writer, it comes with a utility
> called Plextools, which enables you to examine the time-base error on
> your CD-Rs, as well as things like BLER (Block Error Rate). Essential
> for mastering.
>

Seems like an ideal tool for checking the green-pen claim. If there was
an effect, it had to affect the block error rate or time-base errors,
no? Has Stereophile tried doing that?

> John Atkinson
> Editor, Stereophile

 

[Guest]

Archived from groups: rec.audio.high-end (More info?)

Toni <post_to_usenet@hotmail.com> wrote in message
news:<xMfFc.13105$%_6.3916@attbi_s01>...
> En John Atkinson va escriure en 2 Jul 2004 00:12:33 GMT:
> >I wish that were the case. Stereophile has published quite a lot of
> > work showing, basically, that jitter propagates through a D/A system.
> > It can be low-pass filtered but not eliminated unless heroic
> > measures are employed.
>
> AFAIK, for jitter, you only need to read the CD into your laptop
> computer and then play it through the optical out to your
> amplifier.

As I said, "heroic" measures. Not many audiophiles will tolerate a
delay of 60+ minutes before they can hear their music.

> The stability of your PC clock with any medium quality digital I/O
> card will be much greater than the direct read from the rotating CD.

Maybe, maybe not. I don't think you can draw such general conclusions.

John Atkinson
Editor, Stereophile

 

[Guest]

Archived from groups: rec.audio.high-end (More info?)

In message <cc3j7f02icj@news2.newsguy.com>
Timothy A. Seufert (tas@mindspring.com) wrote:
> In article <cc299h01riu@news3.newsguy.com>,
> Stereophile_Editor@Compuserve.com (John Atkinson) wrote:
> > "Timothy A. Seufert" <tas@mindspring.com> wrote in message
> > news:<i6XEc.8236$MB3.1645@attbi_s04>...
> > > as long as the bitstream delivered to the DAC is the same, the
> > > recovered analog signal is the same, within the limits of the DAC.
> >
> > I wish that were the case. Stereophile has published quite a lot of
> > work showing, basically, that jitter propagates through a D/A system.
> > It can be low-pass filtered but not eliminated unless heroic measures
> > are employed.
>
> I'm afraid that I'm not inclined to give Stereophile articles much
> credence when it comes to technical matters, having read many a howler
> whenever said articles are brought to my attention.

Arguing by credential is never very productive, Mr. Seufert. I'd
rather
we stick to the issue at hand. I will return to the subject of
"howlers"
at the end of this posting. In the meantime, if you doubt the articles
in Stereophile, I suggest you read Barry Blesser's compendium on
digital
audio in the October 1978 issue of the Journal of the Audio
Engineering
Society, where the problems of word-clock jitter were first described
in an audio context (to the best of my knowledge).

A Stereophile article showing how different analog signals can be
reconstructed from identical bitstreams can be found at
http/www.stereophile.com/reference/1290jitter. This, too, is based
on
an AES paper, this time by Stephen Harris, and a third article can be
found at http/www.stereophile.com/reference/590jitter. A fourth
article,
showing measured differences, goes up in the stereophile.com archives
on
Monday. Before you dismiss all this work as "howlers," I politely
suggest you should read it.

> It's an entertainment magazine, not an engineering journal.

That may well be true, at least partially, but it doesn't mean that
you are entitled to dismiss everything that is published in
Stereophile.
In the case of the effects of word-clock jitter on the reconstructed
analog signal, I am not aware of anything published in Stereophile
that
is at odds with what has been published in academic journals or
textbooks.
(Note that I am not talking about audibility here, but the observable
effect on the analog signal.)

> > > Jitter in the clock used to write a disc cannot propagate to
> > > playback _as_jitter_, for the simple reason that playback uses an
> > > entirely independent clock source.
> >
> > Again I wish that were the case. Yes, the data recovery clock
> > controls the retrieval of the bitstream from the disc and also
> > controls the word-clock timing of the DAC. But what may be perfect
> > on paper may well not be in practice.
>
> The practice is that there is an oscillator feeding the DAC clock input.
> In order for your claim to be true, somehow random variations away from
> ideal placement of pit/land transitions on the disc must affect that
> oscillator's jitter. This strikes me as more than a little unlikely.

You may think it unlikely, Mr. Seufert, but that doesn't mean it
doesn't
exist. The problem is that there is no clock in the disc data. (The
problem of an AES/EBU datastream, where there is a clock embedded in
the data is somewehat different, but manifests itself in a similar
manner in the DAC.) The CD player's crystal oscillator you mention
must
therefore control both the DAC and the disc rotation. The signal
retrieved
from the rotating disc is actually analog in nature. Much processing
is
therefore required to reconstruct a digital bitstream to be fed to the
DAC, including some kind of memory buffer.

As I wrote, timing uncertainties in the raw data retrieval do appear
to
propagate through this system, resulting in measurable effects in the
recovered analog signal. Things like buffers and PLLs low-pass filter
the timing uncertainty but do not eliminate it, unfortunately.

That a CD-R carrying identical data to a CD can sound different is
described in in article at http/www.stereophile.com/asweseeit/523.

> The only remotely plausible explanation for such an effect that I've
> ever seen put forth is power supply noise, but there are problems with
> that idea too. The biggest being, why should there be any more power
> supply noise than normal? The number of CMOS switching events in the
> digital section of the player should not be any higher on average.

Around 12 years ago, this subject was examined by Ed Meitner and Bob
Gendron in an AES paper. To their surprise, they found -- and I
duplicated their work -- that riding on the DC power rail supplying
the
ICs in a DAC was the audio signal described by the data that was being
processed. If you think about it, this is astonishing. Check it out.

Back to the subject of supposed technical "howlers" in Stereophile
magazine. As editor, I try hard to keep the incidence of errors to an
acceptably low level. When the subject has come up before on r.a.h-e
or
other newsgroups, I have therefore asked the posters to be specific.
If,
indeed, there is a factual error in the magazine, I need to be aware
of
it. There are 4 specific examples in the groups.google.com record:

Example 1: A John Busenitz mentioned, as you have just done, Mr.
Seufert,
the purported high incidence of techical errors in Stereophile. It
turned
out that Mr. Busenitz was only able to cite one example of such an
error,
but it didn't actually appear in Stereophile. It was in a book written
by
Stereophile's one-time technical editor, Robert Harley.

Example 2: I wrote in Stereophile a number of years ago that the AC
signal is not carried in the conductor but in the dielectric around
that conductor. A number of posters seized on this as being a
"howler."
Unfortunately for the critics, my description was technically correct.

Example 3: Tom Nousaine correctly criticized a blind amplifier test
published in a 1989 issue of Stereophile on the grounds that there
were a different number of Same and Different presentations.

Example 4: Arny Krueger has repeatedly criticized the listening tests
performed in Stereophile's reviews on the grounds that the majority of
them are performed sighted. He is correct; they are.

All the other examples mentioned on the newsgroups either appeared in
magazines other than Stereophile; were matters of opinion not fact; or
concerned things, such as Shun Mook tweaks, that the poster thought
unworthy of magazine coverage.

So, Mr. Seufert, if you have a specific example of a technical
"howler"
that was published in Stereophile, please let me know what it was, so
I can ensure we don't make the same error in future. Thank you.

John Atkinson
Editor, Stereophile

 

[Guest]

Archived from groups: rec.audio.high-end (More info?)

On 3 Jul 2004 14:55:52 GMT, Stereophile_Editor@Compuserve.com (John
Atkinson) wrote:

>Toni <post_to_usenet@hotmail.com> wrote in message
> news:<xMfFc.13105$%_6.3916@attbi_s01>...
>> En John Atkinson va escriure en 2 Jul 2004 00:12:33 GMT:
>> >I wish that were the case. Stereophile has published quite a lot of
>> > work showing, basically, that jitter propagates through a D/A system.
>> > It can be low-pass filtered but not eliminated unless heroic
>> > measures are employed.
>>
>> AFAIK, for jitter, you only need to read the CD into your laptop
>> computer and then play it through the optical out to your
>> amplifier.
>
>As I said, "heroic" measures. Not many audiophiles will tolerate a
>delay of 60+ minutes before they can hear their music.

Absolute rubbish if you know *anything* about the technology. A delay
of 4 seconds is more than adequate for *total* buffering and
reclocking. Ask Meridian, who do use this technique in their 800
series. One might have hoped that the Editor of Stereophile would be
aware of this. One might also have hoped that he'd be aware of
asynchronous resampling, as used by the superb (and state of the art,
and reviewed by Stereophile) Benchmark DAC-1..............

--

Stewart Pinkerton | Music is Art - Audio is Engineering

 

[Guest]

Archived from groups: rec.audio.high-end (More info?)

chung <chunglau@covad.net> wrote:
> John Atkinson wrote:
> > "Chelvam" <chelvam@myjaring.net> wrote in message
> > news:<x%gEc.173343$3x.86251@attbi_s54>...
> >> "Timothy A. Seufert" <tas@mindspring.com> wrote in message
> >> news:cbq7b701kqb@news3.newsguy.com...
> >> > So let me get this straight: you are arguing that errors in pit
> >> > lengths resulting in jitter in the signal read from the disc has
> >> > audible effects, even when there are no changes in data values?
> >>
> >> Not me but OEM http/www.daisy-laser.com, they are pretty reputable in
> >> audio industry, aren't they?
> >
> > As a subsidiary of Philips, I guess they are "pretty reputable." BTW,
> > if you have a Plexstor Professional CD-R writer, it comes with a utility
> > called Plextools, which enables you to examine the time-base error on
> > your CD-Rs, as well as things like BLER (Block Error Rate). Essential
> > for mastering.
> >

> Seems like an ideal tool for checking the green-pen claim. If there was
> an effect, it had to affect the block error rate or time-base errors,
> no? Has Stereophile tried doing that?

For how many years did the CD Stoplight make the Stereophile 'Recommended
Comnponents' list, anyway?

Plextools came with all (nonprofessional) Plextor CDRW drives I've bought
in the last few years, btw.

--

-S.
"We started to see evidence of the professional groupie in the early 80's.
Alarmingly, these girls bore a striking resemblance to Motley Crue." --
David Lee Roth

 

[Guest]

Archived from groups: rec.audio.high-end (More info?)

On 3 Jul 2004 14:55:52 GMT, Stereophile_Editor@Compuserve.com (John
Atkinson) wrote:

>As I said, "heroic" measures. Not many audiophiles will tolerate a
>delay of 60+ minutes before they can hear their music.

Hm, the RAM of a PC has lots of jitter due to its refresh cycles.
Thus the samples are stored in the playback buffer of a sound card.
The sound card has a local clock which controls its A/D and D/A chips
and any chips for digital audio i/o.

IMHO it is sufficient to buffer the audio for 10 ms in the buffer of
the sound card. A 60+ minutes buffer is not needed.

Do you happen to know the size of the buffers (note plural) in a
(audio) CD player?

Norbert

 

[Guest]

Archived from groups: rec.audio.high-end (More info?)

"John Atkinson" <Stereophile_Editor@compuserve.com> wrote in message
news:ivOFc.20695$%_6.4910@attbi_s01...
In the meantime, if you doubt the articles
> in Stereophile, I suggest you read Barry Blesser's compendium on
> digital
> audio in the October 1978 issue of the Journal of the Audio
> Engineering
> Society, where the problems of word-clock jitter were first described
> in an audio context (to the best of my knowledge).
>
> an AES paper, this time by Stephen Harris, and a third article can be
> found at http/www.stereophile.com/reference/590jitter. A fourth
> article,
> showing measured differences, goes up in the stereophile.com archives
> on
> Monday. Before you dismiss all this work as "howlers," I politely
> suggest you should read it.
>
> > It's an entertainment magazine, not an engineering journal.
>
> That may well be true, at least partially, but it doesn't mean that
> you are entitled to dismiss everything that is published in
> Stereophile.

It's more than a bit annoying to me (at least) that words to the effect of
information having appeared in academic journals are the equivalent of god's
word. It would help to know if *that* journal uses peer review for
acceptance for publication OR if any and all submitted papers are published.
Even if the former be true, however, there are "errata" and retractions, and
although not very common, such do take place. I'm not in favor of tossing
out published papers or dismissing scientific facts, but am simply saying
that just because some data AND their subsequent *interpretation* and
conclusions have appeared therein, one cannot simply accept such as given
immutable truths.

 

[Guest]

Archived from groups: rec.audio.high-end (More info?)

On Sun, 04 Jul 2004 07:39:58 GMT, Stereophile_Editor@compuserve.com
(John Atkinson) wrote:

>A Stereophile article showing how different analog signals can be
>reconstructed from identical bitstreams can be found at
>http/www.stereophile.com/reference/1290jitter. This, too, is based
>on
>an AES paper, this time by Stephen Harris, and a third article can be
>found at http/www.stereophile.com/reference/590jitter. A fourth article,
>showing measured differences, goes up in the stereophile.com archives on
>Monday. Before you dismiss all this work as "howlers," I politely
>suggest you should read it.

Hardly new knowledge. Jitter has been acknowledged as a problem in
digital audio since the '60s - telecomms being several decades ahead
of so-called 'high end' audio, as usual.

>> > > Jitter in the clock used to write a disc cannot propagate to
>> > > playback _as_jitter_, for the simple reason that playback uses an
>> > > entirely independent clock source.
>> >
>> > Again I wish that were the case.

It is...........

>> > Yes, the data recovery clock
>> > controls the retrieval of the bitstream from the disc and also
>> > controls the word-clock timing of the DAC. But what may be perfect
>> > on paper may well not be in practice.
>>
>> The practice is that there is an oscillator feeding the DAC clock input.
>> In order for your claim to be true, somehow random variations away from
>> ideal placement of pit/land transitions on the disc must affect that
>> oscillator's jitter. This strikes me as more than a little unlikely.
>
>You may think it unlikely, Mr. Seufert, but that doesn't mean it doesn't
>exist. The problem is that there is no clock in the disc data.

Exactly! In a standalone player, the only clock is the free-running
DAC clock, which also controls the data-reading servo. Hence, *if*
that clock has vanishingly low phase noise, and *if* the power
supplies are absolutely clean, there can be no jitter in the output
signal, other than that of the A/D converter used to make the original
digital master.

> (The
>problem of an AES/EBU datastream, where there is a clock embedded in
>the data is somewehat different, but manifests itself in a similar
>manner in the DAC.)

No, it manifests itself in an *entirely* different manner.

> The CD player's crystal oscillator you mention must
>therefore control both the DAC and the disc rotation. The signal retrieved
>from the rotating disc is actually analog in nature.

So what? It still produces a stream of ones and zeros, with an error
rate of less than one in ten *million* from any modern transport mech
and associated electronics. Hardly an audible problem........

> Much processing is
>therefore required to reconstruct a digital bitstream to be fed to the
>DAC, including some kind of memory buffer.

Yes, a FIFO buffer timed by the DAC master clock.

>As I wrote, timing uncertainties in the raw data retrieval do appear to
>propagate through this system, resulting in measurable effects in the
>recovered analog signal. Things like buffers and PLLs low-pass filter
>the timing uncertainty but do not eliminate it, unfortunately.

Unfortunately for your theory, there are *no* PLLs in a well-designed
CD player, and the buffer is a FIFO unit, clocked by the free-running
DAC master clock, so there is *no* attenuation involved, simply a
total *lack* of dependence on the jitter of the raw signal as
retrieved from the disc.

>That a CD-R carrying identical data to a CD can sound different is
>described in in article at http/www.stereophile.com/asweseeit/523.
>
>> The only remotely plausible explanation for such an effect that I've
>> ever seen put forth is power supply noise, but there are problems with
>> that idea too. The biggest being, why should there be any more power
>> supply noise than normal? The number of CMOS switching events in the
>> digital section of the player should not be any higher on average.
>
>Around 12 years ago, this subject was examined by Ed Meitner and Bob
>Gendron in an AES paper. To their surprise, they found -- and I
>duplicated their work -- that riding on the DC power rail supplying the
>ICs in a DAC was the audio signal described by the data that was being
>processed. If you think about it, this is astonishing. Check it out.

It's not really astonishing, but it *is* a sign of poor system design.
See any current Meridian player for a fine example of how it should be
done - or just hook up any old transport to a Benchmark DAC-1.

It's unfortunate that your august publication still makes the fatal
error of assuming that a DAC which actually *is* sensitive to
different transports is somehow 'superior', when the plain *fact* is
that it's basically broken.
--

Stewart Pinkerton | Music is Art - Audio is Engineering

 

[chung]

Archived from groups: rec.audio.high-end (More info?)

Steven Sullivan wrote:

> chung <chunglau@covad.net> wrote:
>> John Atkinson wrote:
>> > "Chelvam" <chelvam@myjaring.net> wrote in message
>> > news:<x%gEc.173343$3x.86251@attbi_s54>...
>> >> "Timothy A. Seufert" <tas@mindspring.com> wrote in message
>> >> news:cbq7b701kqb@news3.newsguy.com...
>> >> > So let me get this straight: you are arguing that errors in pit
>> >> > lengths resulting in jitter in the signal read from the disc has
>> >> > audible effects, even when there are no changes in data values?
>> >>
>> >> Not me but OEM http/www.daisy-laser.com, they are pretty reputable in
>> >> audio industry, aren't they?
>> >
>> > As a subsidiary of Philips, I guess they are "pretty reputable." BTW,
>> > if you have a Plexstor Professional CD-R writer, it comes with a utility
>> > called Plextools, which enables you to examine the time-base error on
>> > your CD-Rs, as well as things like BLER (Block Error Rate). Essential
>> > for mastering.
>> >
>
>> Seems like an ideal tool for checking the green-pen claim. If there was
>> an effect, it had to affect the block error rate or time-base errors,
>> no? Has Stereophile tried doing that?
>
> For how many years did the CD Stoplight make the Stereophile 'Recommended
> Comnponents' list, anyway?

I guess this supports the view that Stereophile is an entertainment
magazine. This also really destroys the credibility of the "Recommended
Components" list, IMO.

>
> Plextools came with all (nonprofessional) Plextor CDRW drives I've bought
> in the last few years, btw.
>

 

[Guest]

Archived from groups: rec.audio.high-end (More info?)

Stewart Pinkerton <patent3@dircon.co.uk> wrote in message
news:<R1PFc.22187$Oq2.18326@attbi_s52>...
> On 3 Jul 2004 14:55:52 GMT, Stereophile_Editor@Compuserve.com (John
> Atkinson) wrote:
> >Toni <post_to_usenet@hotmail.com> wrote in message
> > news:<xMfFc.13105$%_6.3916@attbi_s01>...
> >> En John Atkinson va escriure en 2 Jul 2004 00:12:33 GMT:
> >> >I wish that were the case. Stereophile has published quite a lot
> >> > of work showing, basically, that jitter propagates through a
> >> > D/A system. It can be low-pass filtered but not eliminated unless
> >> > heroic measures are employed.
> >>
> >> AFAIK, for jitter, you only need to read the CD into your laptop
> >> computer and then play it through the optical out to your
> >> amplifier.
> >
> >As I said, "heroic" measures. Not many audiophiles will tolerate a
> >delay of 60+ minutes before they can hear their music.
>
> Absolute rubbish if you know *anything* about the technology. A delay
> of 4 seconds is more than adequate for *total* buffering and
> reclocking.

Two points Stewart. First, is that a 4s buffer falls, I think, under
the category of "heroic" measures. However, the buffer output clock
still needs to be tied to the long-term average of the incoming
dataclock and that is the pathway for low-frequency jitter, unless
the circuit topology is optimal. I have just reviewed a DAC designed
by r.a.p. regular Dan Lavry, who has some intersting ideas on this.

Second, is that I was addressing "Toni"'s suggestion that CD playback
jitter would be eliminated if the disc's content were first stored on
hard disk. Yes, it would be possible to start reading the disc, then
start outputting the data after a delay of about 4s, which would perhaps
be sufficent, but again, this falls under the "heroic measure" heading,
IMO.

> Ask Meridian, who do use this technique in their 800 series.

Yes, Meridian does do this. It should be noted that the players are
_very_ expensive. Normal-priced CD players do not have anything like
4s' worth of FIFO, though with memory as cheap as it is I do not know
why.

John Atkinson
Editor, Stereophile

 

[Guest]

Archived from groups: rec.audio.high-end (More info?)

On Mon, 05 Jul 2004 05:08:41 GMT, Stereophile_Editor@compuserve.com
(John Atkinson) wrote:

>Stewart Pinkerton <patent3@dircon.co.uk> wrote in message
>news:<R1PFc.22187$Oq2.18326@attbi_s52>...
>> On 3 Jul 2004 14:55:52 GMT, Stereophile_Editor@Compuserve.com (John
>> Atkinson) wrote:
>> >Toni <post_to_usenet@hotmail.com> wrote in message
>> > news:<xMfFc.13105$%_6.3916@attbi_s01>...
>> >> En John Atkinson va escriure en 2 Jul 2004 00:12:33 GMT:
>> >> >I wish that were the case. Stereophile has published quite a lot
>> >> > of work showing, basically, that jitter propagates through a
>> >> > D/A system. It can be low-pass filtered but not eliminated unless
>> >> > heroic measures are employed.
>> >>
>> >> AFAIK, for jitter, you only need to read the CD into your laptop
>> >> computer and then play it through the optical out to your
>> >> amplifier.
>> >
>> >As I said, "heroic" measures. Not many audiophiles will tolerate a
>> >delay of 60+ minutes before they can hear their music.
>>
>> Absolute rubbish if you know *anything* about the technology. A delay
>> of 4 seconds is more than adequate for *total* buffering and
>> reclocking.
>
>Two points Stewart. First, is that a 4s buffer falls, I think, under
>the category of "heroic" measures.

Agreed - but not what you said above.

>However, the buffer output clock
>still needs to be tied to the long-term average of the incoming
>dataclock and that is the pathway for low-frequency jitter, unless
>the circuit topology is optimal.

No, it doesn't - that is the whole *point* of genuine reclocking. The
allowable clock frequency tolerance for CDs is such that a 4 second
buffer is adequate to avoid overrun or underrun after 80 minutes. Of
course, Benchmark have shown in the DAC-1 that an asynchronous
re-sampler can provide an equally good solution to incoming jitter,
with no such delay.

>I have just reviewed a DAC designed
>by r.a.p. regular Dan Lavry, who has some intersting ideas on this.
>
>Second, is that I was addressing "Toni"'s suggestion that CD playback
>jitter would be eliminated if the disc's content were first stored on
>hard disk. Yes, it would be possible to start reading the disc, then
>start outputting the data after a delay of about 4s, which would perhaps
>be sufficent, but again, this falls under the "heroic measure" heading,
>IMO.

In terms of applying a 'brute force' solution, yes, but not much of a
drawback to any typical audiophile. Compare and contrast with the time
it takes to put on an LP............

>> Ask Meridian, who do use this technique in their 800 series.
>
>Yes, Meridian does do this. It should be noted that the players are
>_very_ expensive. Normal-priced CD players do not have anything like
>4s' worth of FIFO, though with memory as cheap as it is I do not know
>why.

OTOH, the Benchmark DAC-1, which I believe has been reviewed by
Stereophile, is equally immune to jitter in the incoming datastream,
and costs less than $1,000 - i.e. less than many of your recommended
cables!
--

Stewart Pinkerton | Music is Art - Audio is Engineering

 

[Toni]

Archived from groups: rec.audio.high-end (More info?)

Hi Atkinson and Norbert,

(Oops, and hello to everybody as I just "jumped in" without
presenting me to the group)

please let answer to both in the same post:

En Norbert Hahn va escriure en 4 Jul 2004 14:56:02 GMT:

>On 3 Jul 2004 14:55:52 GMT, Stereophile_Editor@Compuserve.com (John
>Atkinson) wrote:
>
>>As I said, "heroic" measures. Not many audiophiles will tolerate a
>>delay of 60+ minutes before they can hear their music.

A delay of 60+' is not realistic. Most PCs will read a CD in < 8'
+ once you have loaded it it can stay in your hard disk for as
long as you / Windows want.

As for the heroic measure I'm not so sure. A laptop is in the
price range of medium to good speakers and surely less expansive
than what some call "true high-end" transports.

Another advantage, if you want to give the time to it is, that
you can extract the audio with one of those programs that will
re-read the audio blocks as many times as required to guarantee
that they match and there are no bit read errors. This is
impossible to do in real-time in a normal CD reader. This I would
accept in the "heroic measure".

>Hm, the RAM of a PC has lots of jitter due to its refresh cycles.
>Thus the samples are stored in the playback buffer of a sound card.
>The sound card has a local clock which controls its A/D and D/A chips
>and any chips for digital audio i/o.
>
>IMHO it is sufficient to buffer the audio for 10 ms in the buffer of
>the sound card. A 60+ minutes buffer is not needed.

This is completely true. Thinking of it, you don't even need to
pre-read the CD, as the PC is able to read the CD faster than
real time and buffer in RAM. An external USB SPDIF card would
guarantee a second _externally_clocked_ buffer not influenced by
the PC's internal electrical noise. The maniacs could even
replace the card's crystal by a high-quality custom-made one (not
very expensive, most electronics shops will order them for you).

Toni

 

[Guest]

Archived from groups: rec.audio.high-end (More info?)

"Norman Schwartz" <nmsz1@att.net> wrote in message
news:<CvYFc.23081$%_6.1517@attbi_s01>...
> "John Atkinson" <Stereophile_Editor@compuserve.com> wrote in message
> news:ivOFc.20695$%_6.4910@attbi_s01...
> In the meantime, if you doubt the articles
> > in Stereophile, I suggest you read Barry Blesser's compendium on
> > digital audio in the October 1978 issue of the Journal of the
> > Audio Engineering Society, where the problems of word-clock jitter
> > were first described in an audio context (to the best of my
> > knowledge)...
>
> It's more than a bit annoying to me (at least) that words to the
> effect of information having appeared in academic journals are the
> equivalent of god's word. It would help to know if *that* journal uses
> peer review for acceptance for publication...

Papers that are published in the Journal of the AUdio Engineering
Society are indeed peer-reviewed.

John Atkinson
Editor, Stereophile
(Member AES)

 

[Guest]

Archived from groups: rec.audio.high-end (More info?)

In article <_CdGc.27466$IQ4.7481@attbi_s02>,
Toni <post_to_usenet@hotmail.com> wrote:

>The maniacs could even
> replace the card's crystal by a high-quality custom-made one (not
> very expensive, most electronics shops will order them for you).

Curious as to what you mean by "high quality" in this context?

What, exactly, is "low quality" about the stock one?

Isaac