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Is CD burning at slower speeds better?

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June 26, 2004 8:47:38 AM

Archived from groups: rec.audio.tech (More info?)

I was told that burning audio CDs at slower speeds is somehow better
and produces more reliable recordings- is there any truth to this?

More about : burning slower speeds

Anonymous
June 26, 2004 1:44:27 PM

Archived from groups: rec.audio.tech (More info?)

"Jezza" <jezza2412@yahoo.co.uk> wrote in message
news:621c9d53.0406260347.285bb666@posting.google.com...
> I was told that burning audio CDs at slower speeds is somehow better
> and produces more reliable recordings- is there any truth to this?

I have seen tests of various burners and CD's. They usually record with
fewer errors at a speed less than the maximum, but higher than the minimum
for a particular recorder. I think these tests are on the web somewhere, but
don't recall where.
Anonymous
June 26, 2004 5:17:20 PM

Archived from groups: rec.audio.tech (More info?)

On 26 Jun 2004 04:47:38 -0700, jezza2412@yahoo.co.uk (Jezza) wrote:

>I was told that burning audio CDs at slower speeds is somehow better
>and produces more reliable recordings- is there any truth to this?

With older drives, yes. Most modern ones are perfectly capable of
making a good recording at high speed. The manual should give you some
info. Different brands of CDR also give different results, so a bit of
experimentation may be called for.

d
Pearce Consulting
http://www.pearce.uk.com
Related resources
Anonymous
June 26, 2004 6:41:32 PM

Archived from groups: rec.audio.tech (More info?)

On 26 Jun 2004 04:47:38 -0700, jezza2412@yahoo.co.uk (Jezza) wrote:

>I was told that burning audio CDs at slower speeds is somehow better
>and produces more reliable recordings- is there any truth to this?

An optimum speed for older recorders and media used to be 2X. Now I
find it's around 8X.

Sensible hardware and software won't offer inappropriate slow burn
speeds. They may well offer inappropriate high ones - the marketing
department insists on it :-) Find a mid-range speed that produces
reliable results with your hardware and choice of media.

Some stand-alone audio CD burners may still be optimised for slow
burns. Suitable media is becoming rare. Time to move to computer
burning, perhaps :_)
June 26, 2004 10:11:24 PM

Archived from groups: rec.audio.tech (More info?)

"Jezza" <jezza2412@yahoo.co.uk> wrote in message
news:621c9d53.0406260347.285bb666@posting.google.com...
> I was told that burning audio CDs at slower speeds is somehow better
> and produces more reliable recordings- is there any truth to this?

If your criteria in question was to see if slower
speed increases playing probability on more
CD players, answer is yes. Many of the older CD
players may not be ablke to play CDs produced at
speeds 4x and higher speeds. Media type and
burber type also are a factor.

Bubba
Anonymous
June 26, 2004 10:39:07 PM

Archived from groups: rec.audio.tech (More info?)

Jezza wrote:
>
> I was told that burning audio CDs at slower speeds is somehow better
> and produces more reliable recordings- is there any truth to this?


Well, not necessarily more reliable, but occasionally, more accurate.

Let me try to explain :-)

For burning CDs of any sort there is an issue of errors when
writing to disk. If I understand corectly, this is normally not a
big issue at all since the writer shouldn't be rated at a speed
that it cannot write without errors. Error correction is used
when played back. In general, data accuracy can always be
maintained fairly well, even on Audio disks.

However, the real issue that relates to the the OP's question is
a second issue specific to Audio CDs and applies even if there
are no read errors during playback. When playing back an Audio
CD, it is done in real time. A clock signal is recovered from the
bits comeing off of the CD and it is used to convert the digital
signal back to an analog one. all Conversion is done relative to
this clock signal. If the pits burned into the CD aren't spaced
prefectly, this clock signal "jumps around" a little. In the
digital world this is called "jitter". Depending on how the
digital to analog conversion is done in the sound equipment, this
jitter can cause the output analog signal to reproduce with
slight time domain distortions in it. This effect is extremly
small and tends to only be noticable on highly resolving audio systems.

An analogy might be a record player that varies from moment to
moment in speed. The mechanical information on the record is all
there but it's not being converted to analog audio well. The
"time" element of converting the mechanical data into analog
music is being corrupted. There is a type of "time domain
distortion" being introduced in the conversion process.

Obviously, if you are pushing the writer to its maximum speed,
there might be subtle variations in the spacing of the pits. The
data on the disk is exact (i.e., "reliable") but the inconsistent
spacing when played back in an audio system might not produce as
"accurate" a sound. Using a lower write speed just allows the
writer to operated well within its capability and produce a more
even (accurate) spacing of the pits. Again, you can get the
correct data off of the disk, the problem is in converting it to
real time analog music.

An interesting side here is that some audiophiles have discovered
that when they made a duplicate of a store purchased CD, the
duplicate seemed to sound "better" for some reason. The
explanation seems to be that commercial CDs are "pressed" rather
than "burned". The edges of the pits on a pressed CD may not have
the clean edges and spacing that a burned CD run at lower speed
has resulting in potentially higher jitter than the duplicate
might generate. Since the actual data values on the original are
copied exactly onto the duplicate, it's 100% reliable and no data
is lost, however, the duplicat CD may have less jitter when
played back in real time.

Note again that this effect is very subtle and in general is not
going to be detected on many systems, even if the difference the
writer has in accuracy between fastest and slowest speeds is
great. On highly resolving systems, jitter's effects can be
noticed, however, the difference in jitter from a CD burned at 2x
and one at 12x on a 12x burner (all other things being equal)
might still be quite subtle and as a result is subject to much
discussion in the high end audio forums :-)

Bottom line? My opinion is that the effects are subtle enough
that it is more a matter of how much time I have to wait for the
thing to burn :-) If you have a fairly high quality sound system,
knock the burn rate down a notch or so it you have the time, but
if the CDs are for playing in the car or a walkman, blast away as
fast as you can.

All this is only IMHO of course!

- Jeff
Anonymous
June 27, 2004 12:36:23 AM

Archived from groups: rec.audio.tech (More info?)

Jeff Wiseman <wisemanja@earthlink.net> wrote in
news:40DDC277.975C87C4@earthlink.net:


> Well, not necessarily more reliable, but occasionally, more accurate.
>
> Let me try to explain :-)

Only if your explanation is accurate -- this one isn't even close. If the
data is retrievable without errors, then the burner was running at an
acceptable speed.

> [snip]
> A clock signal is recovered from the bits comeing off of the CD

This is false -- there are no clock signals contained in the CD data. The
clock signal is generated by the CD player's circuitry. The CD itself
contains encoded data and correction information only, and even that
information is intentionally scattered across the disk.

> If the pits burned into the CD aren't spaced prefectly,

A CD-ROM doesn't contain any "pits" -- the burning process only changes the
optical properties of the media.

> this clock signal "jumps around" a little. In the
> digital world this is called "jitter". Depending on how the
> digital to analog conversion is done in the sound equipment, this
> jitter can cause the output analog signal to reproduce with
> slight time domain distortions in it. This effect is extremly
> small and tends to only be noticable on highly resolving audio systems.
> [snip]

CDs don't work this way at all. The data on a CD isn't even in the correct
order when read back by the player -- blocks of data are intentionally
scattered and interleaved with error correction data, and the data itslef
is encoded to a different form.

It really isn't possible for "pit spacing" to have any effect on the D/A
jitter. The *only* way to read data from a CD requires that the data be
read into memory buffers, de-interleaved, and decoded back into the
original 16 bit samples. Only then is the data in a form to be fed into
the D/A converter, and only at that point does clock timing (and jitter)
come into play.

The "pit spacing" is completely irrelevant -- the data represented by those
pits is a mathematical encoding, which must be decoded and error corrected
before being fed to the D/A converter. The timing of the raw data is
completely separate from the timing of the final data being fed to the D/A.

Here is a web page that explains some of the details:
http://www.ee.washington.edu/conselec/CE/kuhn/cdaudio2/...

In particular, read part II, which describes how the data is encoded and
interleaved before being written to the disk.


> An analogy might be a record player that varies from moment to
> moment in speed. The mechanical information on the record is all
> there but it's not being converted to analog audio well. The
> "time" element of converting the mechanical data into analog
> music is being corrupted. There is a type of "time domain
> distortion" being introduced in the conversion process.

This analogy is completely useless -- the only way for a CD to be read
involves changing the speed of the read head on a continuous basis. CD
players contain read buffers, and the disk will speed up or slow down in
order to keep those buffers full. From there, the data is fed into the
decoding circuitry, which decodes the raw EFM data, removes the
interleaving, performs error checking and correction, and finally feeds the
resulting 16 bit samples into buffers for feeding to the D/A converter.
Any jitter arises from poor clock circuitry that is taking the data from
those final buffers and feeding it into the D/A converter, and has nothing
to do with how the data is being read from the disk.

> An interesting side here is that some audiophiles have discovered
> that when they made a duplicate of a store purchased CD, the
> duplicate seemed to sound "better" for some reason.

Probably for the same reason that they hear improvements when supporting
their speaker cables on blocks of exotic woods (no, I am not joking here --
some of them actually believe this).
Anonymous
June 27, 2004 2:41:21 AM

Archived from groups: rec.audio.tech (More info?)

"Jezza" <jezza2412@yahoo.co.uk> ha scritto nel messaggio
news:621c9d53.0406260347.285bb666@posting.google.com...
> I was told that burning audio CDs at slower speeds is somehow better
> and produces more reliable recordings- is there any truth to this?

I tested that cds burned at 8x max plays on every cdplayer.

16x or over don't.

bye
stef
Anonymous
June 27, 2004 6:49:53 AM

Archived from groups: rec.audio.tech (More info?)

"Jeff Wiseman" <wisemanja@earthlink.net> wrote in message
news:40DDC277.975C87C4@earthlink.net...
>
>
> Jezza wrote:
> >
> > I was told that burning audio CDs at slower speeds is somehow better
> > and produces more reliable recordings- is there any truth to this?
>
>
> Well, not necessarily more reliable, but occasionally, more accurate.
>
> Let me try to explain :-)
>
> For burning CDs of any sort there is an issue of errors when
> writing to disk. If I understand corectly, this is normally not a
> big issue at all since the writer shouldn't be rated at a speed
> that it cannot write without errors. Error correction is used
> when played back. In general, data accuracy can always be
> maintained fairly well, even on Audio disks.
>
> However, the real issue that relates to the the OP's question is
> a second issue specific to Audio CDs and applies even if there
> are no read errors during playback. When playing back an Audio
> CD, it is done in real time. A clock signal is recovered from the
> bits comeing off of the CD and it is used to convert the digital
> signal back to an analog one. all Conversion is done relative to
> this clock signal. If the pits burned into the CD aren't spaced
> prefectly, this clock signal "jumps around" a little. In the
> digital world this is called "jitter". Depending on how the
> digital to analog conversion is done in the sound equipment, this
> jitter can cause the output analog signal to reproduce with
> slight time domain distortions in it. This effect is extremly
> small and tends to only be noticable on highly resolving audio systems.

It is not real time. The data is read into a small buffer where it is
processed by the CPU. The spindle motor is constantly changing speed so,
real time would be an issue. The CPU must have a storage space to fix data
errors and allow time to recover from the speed adjustments and mistracks
from minor bumps and such.
John


> An analogy might be a record player that varies from moment to
> moment in speed. The mechanical information on the record is all
> there but it's not being converted to analog audio well. The
> "time" element of converting the mechanical data into analog
> music is being corrupted. There is a type of "time domain
> distortion" being introduced in the conversion process.
>
> Obviously, if you are pushing the writer to its maximum speed,
> there might be subtle variations in the spacing of the pits. The
> data on the disk is exact (i.e., "reliable") but the inconsistent
> spacing when played back in an audio system might not produce as
> "accurate" a sound. Using a lower write speed just allows the
> writer to operated well within its capability and produce a more
> even (accurate) spacing of the pits. Again, you can get the
> correct data off of the disk, the problem is in converting it to
> real time analog music.
>
> An interesting side here is that some audiophiles have discovered
> that when they made a duplicate of a store purchased CD, the
> duplicate seemed to sound "better" for some reason. The
> explanation seems to be that commercial CDs are "pressed" rather
> than "burned". The edges of the pits on a pressed CD may not have
> the clean edges and spacing that a burned CD run at lower speed
> has resulting in potentially higher jitter than the duplicate
> might generate. Since the actual data values on the original are
> copied exactly onto the duplicate, it's 100% reliable and no data
> is lost, however, the duplicat CD may have less jitter when
> played back in real time.
>
> Note again that this effect is very subtle and in general is not
> going to be detected on many systems, even if the difference the
> writer has in accuracy between fastest and slowest speeds is
> great. On highly resolving systems, jitter's effects can be
> noticed, however, the difference in jitter from a CD burned at 2x
> and one at 12x on a 12x burner (all other things being equal)
> might still be quite subtle and as a result is subject to much
> discussion in the high end audio forums :-)
>
> Bottom line? My opinion is that the effects are subtle enough
> that it is more a matter of how much time I have to wait for the
> thing to burn :-) If you have a fairly high quality sound system,
> knock the burn rate down a notch or so it you have the time, but
> if the CDs are for playing in the car or a walkman, blast away as
> fast as you can.
>
> All this is only IMHO of course!
>
> - Jeff
Anonymous
June 27, 2004 8:38:49 AM

Archived from groups: rec.audio.tech (More info?)

Murray Peterson wrote:
>
> Jeff Wiseman <wisemanja@earthlink.net> wrote in
> news:40DDC277.975C87C4@earthlink.net:
>
> > Well, not necessarily more reliable, but occasionally, more accurate.
> >
> > Let me try to explain :-)
>
> Only if your explanation is accurate -- this one isn't even close. If the
> data is retrievable without errors, then the burner was running at an
> acceptable speed.


As I mentioned further down in my note, the issue has nothing to
do with correctly reading the data. My entire issue had to do
with converting it back to an analog signal.


> > A clock signal is recovered from the bits comeing off of the CD
>
> This is false -- there are no clock signals contained in the CD data. The
> clock signal is generated by the CD player's circuitry. The CD itself
> contains encoded data and correction information only, and even that
> information is intentionally scattered across the disk.


I might be really missing the mark here but this statement of
yours seems to indicate that you don't have a clue what clock
recovery and jitter issues involve. Yes, the clock signal is
generated by the CD player's circuitry, but it is NOT free
running, otherwise you would be constantly overrunning or
underrunning your data buffers. The term "clock recovery" is the
standard term for this process. In reality, the clock is
"derived" from the flow of data bits being read. It is
semi-locked in a way with the databits coming off of the CD.
That's how it knows how fast to run. If the average rate of music
data samples coming off of the disk is a bit slow or fast, the
clock must adjust to compensate. The clock is constantly
adjusting by design based on the timeing of the leading edge of
pits. If the edge spacing varys a lot, the clock also adjusts lot
(jitter).

I may be mistaking in some of my understanding of these things
and I invite correction. However, it does appear that you may
need to read up some on the concepts of clock recovery, jitter,
and their effects on real time D/A conversion.


> > If the pits burned into the CD aren't spaced prefectly,
>
> A CD-ROM doesn't contain any "pits" -- the burning process only changes the
> optical properties of the media.


I stand corrected. On a CD-ROM I believe that the laser burns a
"hole" in the reflective area instead of the pit that exists in a
pressed CD. For all intents and purposes, the function of the pit
and/or hole is the same for discussion on jitter and I carelessly
used them interchangebly.


> > this clock signal "jumps around" a little. In the
> > digital world this is called "jitter". Depending on how the
> > digital to analog conversion is done in the sound equipment, this
> > jitter can cause the output analog signal to reproduce with
> > slight time domain distortions in it. This effect is extremly
> > small and tends to only be noticable on highly resolving audio systems.
> > [snip]
>
> CDs don't work this way at all. The data on a CD isn't even in the correct
> order when read back by the player -- blocks of data are intentionally
> scattered and interleaved with error correction data, and the data itslef
> is encoded to a different form.


I disagree, CDs DO work this way (with some variances in design).
It's not about where the data is on disk and how it comes off,
it's about the rate that it comes off and how it affects the clock.


> It really isn't possible for "pit spacing" to have any effect on the D/A
> jitter. The *only* way to read data from a CD requires that the data be
> read into memory buffers, de-interleaved, and decoded back into the
> original 16 bit samples. Only then is the data in a form to be fed into
> the D/A converter, and only at that point does clock timing (and jitter)
> come into play.


My understanding was always that the clock is derived directly
from pit spacing. If jitter doesn't come from that, where does it
come from? Also, clock timeing is used to drive ALL of the
buffering, de-interleaving, etc. functions that were just
mentioned, not just the D/A conversion.



> The "pit spacing" is completely irrelevant -- the data represented by those
> pits is a mathematical encoding, which must be decoded and error corrected
> before being fed to the D/A converter. The timing of the raw data is
> completely separate from the timing of the final data being fed to the D/A.


If so, then how do you prevent buffer over/underuns in all of the
functions that you just mentioned above?


> Here is a web page that explains some of the details:
> http://www.ee.washington.edu/conselec/CE/kuhn/cdaudio2/...
>
> In particular, read part II, which describes how the data is encoded and
> interleaved before being written to the disk.


I don't see how any of that article changes anything. Jitter is
introduced as a real time product of taking the data off the disk
and converting it. In fact, jitter can be seen in the eye
pattern. According to the article, that comes from the pit
frequency of different bit streams, right?

If I'm totally in left field here, fine I need to know. But give
me a article on jitter introduction in the CD play'er circuitry
and clock recovery. Not one that just talks about data
distribution and redundancy encoding. That doesn't tell me
anything about the issue here in question.


> > An analogy might be a record player that varies from moment to
> > moment in speed. The mechanical information on the record is all
> > there but it's not being converted to analog audio well. The
> > "time" element of converting the mechanical data into analog
> > music is being corrupted. There is a type of "time domain
> > distortion" being introduced in the conversion process.
>
> This analogy is completely useless -- the only way for a CD to be read
> involves changing the speed of the read head on a continuous basis. CD
> players contain read buffers, and the disk will speed up or slow down in
> order to keep those buffers full. From there, the data is fed into the
> decoding circuitry, which decodes the raw EFM data, removes the
> interleaving, performs error checking and correction, and finally feeds the
> resulting 16 bit samples into buffers for feeding to the D/A converter.
> Any jitter arises from poor clock circuitry that is taking the data from
> those final buffers and feeding it into the D/A converter, and has nothing
> to do with how the data is being read from the disk.


Maybe not as useless as you think. The transport drive is all
controlled off the clock and in some systems, the transport
mechanism itself originates the clock.

So I'm still not sure where you are saying that you think jitter
originates. From the above statement it sounds like you believe
it originates somewhere when the reconstructed data is passed to
the D/A. It's the same clock that drives all of the transport and
decoding functions. Jitter is introduced at wherever the clock is
derived from. If the clock is free-wheeling, Then it's the clock
crystal/oscillator itself. But that's not possible because it has
to adjust for read speed variations (at a bit level). So where is
the clock synching/adjusting occur?


> > An interesting side here is that some audiophiles have discovered
> > that when they made a duplicate of a store purchased CD, the
> > duplicate seemed to sound "better" for some reason.
>
> Probably for the same reason that they hear improvements when supporting
> their speaker cables on blocks of exotic woods (no, I am not joking here --
> some of them actually believe this).


Very highly resolving audio equipment can reveal a lot, many
things of which is hard to describe so like anything else, there
is a lot of snake oil there. However, as an original critic
myself, I've spent a lot of hours listening to some very well
matched systems and it's NOT all bogus. Cables can make a
SUBSTANTIAL difference on many systems, but they make no
noticable difference at all on many more mediocre type systems.
Be careful of judging purely on assumed logic without actually
sitting down and exploring it first in an unbiased fashion. I
have no idea of why cables might make such a major difference in
some cases and no noticable difference in others. I have my
theories and other have theirs. All I know is that in fact it
does occur is fascinating and the effects are desirable to those
who experience them.

I also know that a lot of people pass up the opportunity to have
unique experiences because they've already convinced themselves
that some things are impossible.

- Jeff
Anonymous
June 27, 2004 9:11:47 AM

Archived from groups: rec.audio.tech (More info?)

In article <40DE4F12.F3337BEF@earthlink.net>,
Jeff Wiseman <wisemanja@earthlink.net> wrote:

>> This is false -- there are no clock signals contained in the CD data. The
>> clock signal is generated by the CD player's circuitry. The CD itself
>> contains encoded data and correction information only, and even that
>> information is intentionally scattered across the disk.
>
>
>I might be really missing the mark here but this statement of
>yours seems to indicate that you don't have a clue what clock
>recovery and jitter issues involve. Yes, the clock signal is
>generated by the CD player's circuitry, but it is NOT free
>running, otherwise you would be constantly overrunning or
>underrunning your data buffers. The term "clock recovery" is the
>standard term for this process. In reality, the clock is
>"derived" from the flow of data bits being read. It is
>semi-locked in a way with the databits coming off of the CD.
>That's how it knows how fast to run. If the average rate of music
>data samples coming off of the disk is a bit slow or fast, the
>clock must adjust to compensate. The clock is constantly
>adjusting by design based on the timeing of the leading edge of
>pits. If the edge spacing varys a lot, the clock also adjusts lot
>(jitter).
>
>I may be mistaking in some of my understanding of these things
>and I invite correction. However, it does appear that you may
>need to read up some on the concepts of clock recovery, jitter,
>and their effects on real time D/A conversion.

You are mistaken in at least some of your understanding. I'd suggest
referring to a basic text on digital audio, such as one of Ken
Pohlmann's, for the details.

Briefly, though: there are two interesting cases to look at -
single-box CD players, and transport/DAC systems connected by S/PDIF
or similar path. Let's look at the single-box CD player first, as
it's the simpler case.

In a single-box player of competent design, the timing of the
conversion between the final digital samples, and analog voltages, is
controlled by a quartz-crystal operator running at a fixed speed...
period. The conversion rate is _not_ derived from a clock recovered
from the data arriving from the spinning disc - the disc speed does
not control the conversion process. It's very much the other way
around. The data is clocked out of the Reed-Solomon C2/C2 error
correction and de-interleaving chip at a very predictable rate
(controlled by the fixed-speed quartz oscillator). Raw data arriving
from the CD is fed into the de-interleaver at whatever rate it's
happening to arrive.

As you point out, this can cause buffer underflow/overflow in the
correction chip, due to the difference in the clock rates between
"data arriving" and "data leaving". The CD player controller prevents
this, by adjusting the rate at which the CD is spinning (in rather
coarse increments), so that the "data arriving" rate varies as needed
to keep the buffer's fill level within acceptable bounds. The "data
leaving the chip and being converted to analog" rate does _not_
change.

As a result of this process, a single-box player of good design is (or
should be) quite immune to small variations in the pit/land timing.
The clock recovered from the raw pit/land data is used only to control
the feeding of the data _into_ the error-correction chip - when the
data comes out of the chip, it's under the control of a much more
stable, fixed-speed, as-low-in-jitter-as-you-care-to-engineer-it
oscillator. Timing jitter in the incoming-data data is simply
stripped out by the de-interleaving process.

Things get a bit more complicated in the case of a transport/DAC
two-box system. The process works much as above, until the data is
clocked out of the error-correction chip. In this case, instead of it
going right into a DAC chip, it's fed to an S/PDIF encoder/transmitter
chip, which Manchester-encodes (I think) the data and sents it out the
optical or RCA or XLR connector.

The DAC-box must then receive this encoded data, recover a clock
signal from it, recover the data, and convert the data to analog. A
lot of DAC-boxes do a rather poor job of the clock recovery and
conversion, and the conversion timing is rather jitter-prone. This
jitter is from the S/PDIF encoding/decoding process, _not_ from the
jitter in the pit/land timings, though - as in the case of a
single-box player, the pit/land timing jitter was stripped out when
the data was fed through the error-correction and de-interleaving
process.

The jitter in the S/PDIF process occurs for a number of reasons... the
finite rise and fall time of the S/PDIF electrical or optical signal,
electrical noise, the sensitivity of certain S/PDIF receivers to the
pattern of the data arriving, and to the electrical behavior of the
the phase-locked loop circuits often used in clock recovery.

It's possible for an external DAC box to do a good job of clock
recovery (or re-creation), but many do not.

>> A CD-ROM doesn't contain any "pits" -- the burning process only changes the
>> optical properties of the media.
>
>
>I stand corrected. On a CD-ROM I believe that the laser burns a
>"hole" in the reflective area instead of the pit that exists in a
>pressed CD. For all intents and purposes, the function of the pit
>and/or hole is the same for discussion on jitter and I carelessly
>used them interchangebly.

My undererstanding is that in a "manufactured" CD (whether
digital-audio or CD-ROM) there actually are physical pits and lands.
They're created by an injection-molding process, with the "negatives"
of the pits and lands having been formed in the mold/stamper.

In a CD-R, the laser makes physical changes in a layer of organic dye
on the disc... I don't know whether this actually "burns" it away, or
just changes it from reflective to nonreflective.

In a CD-RW, the laser changes the phase of a thin layer of rare-earth
alloy from crystalline to amorphous, or vice versa, and thus changes
its reflectivity.

>My understanding was always that the clock is derived directly
>from pit spacing.

The _first_ clock, used to transfer the data into the Reed-Solomon
error correction chip, is derived from the pit spacing. However, this
clock is _not_ used in the actual digital-to-analog conversion
process... it plays no further role once the data has started its way
into the error corrector / de-interleaver.

The clock which controls the D-to-A step is a separate, independent
one.

--
Dave Platt <dplatt@radagast.org> AE6EO
Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!
Anonymous
June 27, 2004 10:07:35 AM

Archived from groups: rec.audio.tech (More info?)

dplatt@radagast.org (Dave Platt) wrote in
news:10dsloj82vmb695@corp.supernews.com:

> [snip]

Nice post -- I'll forgo any response of my own, since yours covers the
details so nicely.
Anonymous
June 27, 2004 2:01:37 PM

Archived from groups: rec.audio.tech (More info?)

Jezza wrote:

> I was told that burning audio CDs at slower speeds is somehow better
> and produces more reliable recordings- is there any truth to this?

Error rate is likely to be lowest at some speed setting for some
combination of media and burner, but you need to determine actual error
rate with actual media and actual burner to have knowledge. If you want
to assume: don't use the fastest setting, don't use the slowest setting,
use a "moderately slow" setting, on an old burner that cold be X2, on a
new it could be X8 or x12 .... note: examples from thin air, not
verified except that I know that a "problem cd player" is more likely to
play things that are burned x2 on my no longer new Plextor than things
that are burned at max speed, x8.


Kind regards

Peter Larsen

--
*******************************************
* My site is at: http://www.muyiovatki.dk *
*******************************************
Anonymous
June 27, 2004 2:01:54 PM

Archived from groups: rec.audio.tech (More info?)

Dave,

> the "data arriving" rate varies as needed to keep the buffer's fill level
within acceptable bounds. <

I agree with Murray, that really was a great post.

Apparently it's a very common misconception that errors in the data spacing
on a CD surface create jitter, because I see this wrongly stated all the
time. All modern CD drives can read fast enough to keep the buffer full. And
once the data is in a buffer, the CD's clock can send it out as accurately
as it's capable of.

--Ethan
Anonymous
June 27, 2004 3:48:50 PM

Archived from groups: rec.audio.tech (More info?)

On Sat, 26 Jun 2004 22:41:21 GMT, "s.stef" <COMEILNOME@libero.it>
wrote:

>> I was told that burning audio CDs at slower speeds is somehow better
>> and produces more reliable recordings- is there any truth to this?
>
>I tested that cds burned at 8x max plays on every cdplayer.
>
>16x or over don't.

That agrees with my experience.

Want to carry on? Does your burner/software/media offer slower burn
speeds? If you CAN burn at 2X (maybe even 1X) are the results good?
Anonymous
June 27, 2004 3:51:54 PM

Archived from groups: rec.audio.tech (More info?)

On Sun, 27 Jun 2004 10:01:37 +0200, Peter Larsen
<SPAMSHIELD_plarsen@mail.tele.dk> wrote:

>note: examples from thin air, not
>verified except that I know that a "problem cd player" is more likely to
>play things that are burned x2 on my no longer new Plextor than things
>that are burned at max speed, x8.

Whereas on my newer Plextor, using "high speed" media, I get failures
at speeds both higher and lower than the (apparently) optimal 8X.

We've all got to find our own "sweet spot" it appears.
June 27, 2004 8:22:25 PM

Archived from groups: rec.audio.tech (More info?)

"Jeff Wiseman" <wisemanja@earthlink.net> wrote in message
news:40DE4F12.F3337BEF@earthlink.net...
>
>
>
> I might be really missing the mark here but this statement of
> yours seems to indicate that you don't have a clue what clock
> recovery and jitter issues involve. Yes, the clock signal is
> generated by the CD player's circuitry, but it is NOT free
> running, otherwise you would be constantly overrunning or
> underrunning your data buffers. The term "clock recovery" is the
> standard term for this process. In reality, the clock is
> "derived" from the flow of data bits being read. It is
> semi-locked in a way with the databits coming off of the CD.
> That's how it knows how fast to run. If the average rate of music
> data samples coming off of the disk is a bit slow or fast, the
> clock must adjust to compensate. The clock is constantly
> adjusting by design based on the timeing of the leading edge of
> pits. If the edge spacing varys a lot, the clock also adjusts lot
> (jitter).

Let em ask a stupid question based on your thesis of clock speed
from the data flow. Can I burn some tracks of an audio CD at speed X,
not finalize the CD, burn more tracks at speed Y and then finalize the CD.
Would it play correctly in a CD player?

>
> - Jeff
Anonymous
June 27, 2004 8:59:06 PM

Archived from groups: rec.audio.tech (More info?)

> That agrees with my experience.
>
> Want to carry on? Does your burner/software/media offer slower burn
> speeds? If you CAN burn at 2X (maybe even 1X) are the results good?

I think not.

4x to 8x are good speeds.
probably 8x is the best choise

bye
Anonymous
June 27, 2004 11:26:23 PM

Archived from groups: rec.audio.tech (More info?)

Dave Platt wrote:
>
> You are mistaken in at least some of your understanding. I'd suggest
> referring to a basic text on digital audio, such as one of Ken
> Pohlmann's, for the details.


Thanks for that. I think I'm getting more of a handle on this...


> The clock recovered from the raw pit/land data is used only to control
> the feeding of the data _into_ the error-correction chip - when the
> data comes out of the chip, it's under the control of a much more
> stable, fixed-speed, as-low-in-jitter-as-you-care-to-engineer-it
> oscillator


Ok, so data being passed to the D/A in general should always
convert on an accurate timing basis. The clock running the
converter also controls the transport speed to prevent
overflow/underflow problems. This is where I missed the point as
most of my experience in telecomm systems and separate DACs don't
have this clock feedback mechanism (i.e., the rate of reception
cannot be controlled). The D/A clock recovery came from the
incoming data stream as you've described for the separate D/A
scenario. One clock ran it all.


> Timing jitter in the incoming-data data is simply
> stripped out by the de-interleaving process.


And hopefully, the read errors introduced by jitter in the clock
recovered from the bit reads of the disc have been all corrected
in the de-interleaving and error correction circuits prior to the D/A.


> The _first_ clock, used to transfer the data into the Reed-Solomon
> error correction chip, is derived from the pit spacing. However, this
> clock is _not_ used in the actual digital-to-analog conversion
> process... it plays no further role once the data has started its way
> into the error corrector / de-interleaver.


OK, so jitter in the clock recovered from pit spacing does not
affect the D/A conversion process itself. However, I know that
read errors due to jitter, misalignment/laser focus, etc., can
become great enough that even after "read error correction", the
read data may still have errors in it when passed off to the D/A
converter. Error correction algorithms are likely done in a way
to minimize these "bad data samples" but none-the-less bad values
can occasionally be sent to the DAC.

So uneven pit spacing causes jitter which causes read errors...

Now this is an area that I'm not really familiar with. How bad
does jitter have to be before read errors start affecting the
data stream to the DACs? How often does data samples with minor
faults occur? Unlike a non-real time arrangment like reading a
data file off of a hard disk where a signal from the decoding
circuitry can indicate a failed read so another attempt can be
made, when you get data off an audio disk you only have a fixed
amount of time to take care of this. Even with "skip-protection"
you only have so many reads for majority voting before you run
out of time. With a bad piece of sample data that can't be
totally corrected, you have to eventually send something to the DAC.

I've seen two distinct sets of opinions on this but not a lot of
evidence. One group says that once the data is read ,
de-interleaved, error corrected, etc., it will never, never,
ever, ever be a wrong value because it has been "error
corrected". Error correction algorithms are limited in many ways
and when you are limited in time and read passes, I find it
difficult to believe that every sample will be error-free at all
times. Also, I've listened to systems that seemed to have a
slight noise problem and occasionally skipped before being fixed
with a realignment and readjustment for tracking of the laser
heads to reduce read errors. They can sound different. Sometimes
when errors exist, some can get through to affect the sound. I've
heard it.

Again, we're talking about typical CD players here, not the type
that can read at 12x and do real time majority voting to ensure
accurate reads before even starting the error-correction process.

So am I missing something here? Does anyone have the experience
to show that worst case jitter due to pit timing for a standard
red book CD can NEVER reach the point of showing up as false data
in the output stream? Or is my original statement true where
significant pit spacing uneveness CAN show up in the output in
some form or another?

- Jeff
Anonymous
June 27, 2004 11:46:06 PM

Archived from groups: rec.audio.tech (More info?)

On Sat, 26 Jun 2004 20:36:23 GMT, Murray Peterson
<mwp@home.com.invalid> wrote:

>> [snip]
>> A clock signal is recovered from the bits comeing off of the CD
>
>This is false -- there are no clock signals contained in the CD data. The
>clock signal is generated by the CD player's circuitry. The CD itself
>contains encoded data and correction information only, and even that
>information is intentionally scattered across the disk.

The CD contains an imbedded clock which needs to be recoverd in
the receiver circuit and it is used to clock the input circuit of the
de-interleave buffer. Failing to synch to this clock causes mis-reads
of the CD, jitter in the pit spacing will increase the read error rate
(C11 errors).

The embedded clock signal is de-coupled from other CD clocks and
thusly from the D/A converter clock by the de-interleave buffer.

Norbert
Anonymous
June 28, 2004 2:28:00 AM

Archived from groups: rec.audio.tech (More info?)

Jeff Wiseman <wisemanja@earthlink.net> wrote in
news:40DF1F17.E925002@earthlink.net:

> OK, so jitter in the clock recovered from pit spacing does not
> affect the D/A conversion process itself. However, I know that
> read errors due to jitter, misalignment/laser focus, etc., can
> become great enough that even after "read error correction", the
> read data may still have errors in it when passed off to the D/A
> converter. Error correction algorithms are likely done in a way
> to minimize these "bad data samples" but none-the-less bad values
> can occasionally be sent to the DAC.

Yes.

> So uneven pit spacing causes jitter which causes read errors...

It's possible, but unlikely, at least in the way you are describing it.
Each pit or land on a CD doesn't represent a single bit. The data on a CD
is in EFM (eight to fourteen modulation), which is used to minimize the
number of 1 to 0 or 0 to 1 transitions. Using EFM ensures that each pit
comes in a length of 3 to 11 bits -- you should think of the pits as
something more like "stripes". Spacing errors can therefore only occur
every 3 to 11 bits, the remainder of the data within one of these stripes
has no leading edge.

Here is a quick description of EFM:
http://www.ee.washington.edu/conselec/CE/kuhn/cdmulti/9...


> Now this is an area that I'm not really familiar with. How bad
> does jitter have to be before read errors start affecting the
> data stream to the DACs?

Bad enough to cause the reading circuitry to completely misread the value
of a bit, and even then, the error correction circuitry can easily correct
most of these errors. To have an effect on the data being fed to the DAC,
the error rate has to be very bad indeed.

If you want a detailed analysis of the error correction capabilities of a
CD, google for "cross interleaved Reed Solomon" (CIRC in short).

> How often does data samples with minor faults occur?

Errors occur quite frequently, but they are almost always correctable.
Here are some tests done for various CD burners:
www.cdrinfo.com/Sections/Articles/Specific.asp?ArticleH...
832S&index=9

> I've seen two distinct sets of opinions on this but not a lot of
> evidence. One group says that once the data is read ,
> de-interleaved, error corrected, etc., it will never, never,
> ever, ever be a wrong value because it has been "error
> corrected".

CDs are very good at correcting errors, but anyone can take an Exacto knife
and force it to have uncorrectable errors. However, if the errors were
corrected, then the data is definitely perfect -- that's what data
correction is for.

> So am I missing something here? Does anyone have the experience
> to show that worst case jitter due to pit timing for a standard
> red book CD can NEVER reach the point of showing up as false data
> in the output stream? Or is my original statement true where
> significant pit spacing uneveness CAN show up in the output in
> some form or another?

"never" is too absolute. However, the error detection and correction
abilities of a CD are amazing; for example, the CIRC code can correct burst
errors of up to 3500 bits. That's more than a few simple bit errors, and
for pit spacing to cause uncorrectable errors, the entire CD would have to
be considered as faulty. I would also expect it to sound positively
horrible -- clicks, interpolated sections, and muted sections don't make
for a good listening experience.
Anonymous
June 28, 2004 5:00:24 PM

Archived from groups: rec.audio.tech (More info?)

Sat, 26 Jun 2004 09:44:27 -0600, "Mark A" <nobody@switchboard.net>
pisze:

>I have seen tests of various burners and CD's. They usually record with
>fewer errors at a speed less than the maximum, but higher than the minimum
>for a particular recorder. I think these tests are on the web somewhere, but
>don't recall where.

http://www.cdrinfo.com/Sections/Hardware/All.asp


--
Pozdrowienia

Andrzej Popowski
Anonymous
June 28, 2004 9:10:29 PM

Archived from groups: rec.audio.tech (More info?)

On Sun, 27 Jun 2004 16:59:06 GMT, "s.stef" <COMEILNOME@libero.it>
wrote:

>> Want to carry on? Does your burner/software/media offer slower burn
>> speeds? If you CAN burn at 2X (maybe even 1X) are the results good?
>
>I think not.
>
>4x to 8x are good speeds.
>probably 8x is the best choise


You think? Have you tried?
Anonymous
June 30, 2004 1:25:45 AM

Archived from groups: rec.audio.tech (More info?)

Laurence Payne wrote:
> On Sun, 27 Jun 2004 16:59:06 GMT, "s.stef" <COMEILNOME@libero.it>
> wrote:
>
>>> Want to carry on? Does your burner/software/media offer slower
>>> burn speeds? If you CAN burn at 2X (maybe even 1X) are the results
>>> good?
>>
>> I think not.
>>
>> 4x to 8x are good speeds.
>> probably 8x is the best choise
>
>
> You think? Have you tried?

I have, and I do.

geoff
Anonymous
July 14, 2004 9:37:52 AM

Archived from groups: rec.audio.tech (More info?)

Steven Sullivan wrote:
<<stuff deleted>>
> <sigh>
> I suspect it's more likely just bad comparison techniques.
> If they improved those, changing cables probably wouldn't
> yield much in the way of statistically significant perceived
> differences.
>
> But I would still like to know if any *measurements*, at least,
> have been done to verify that many two-box systems still do not do
> clock recovery well. At what point their measurable performance
> translates to an audible difference, is another issue.


would be most interesting...


> I'm sorry, Jeff, but as you might have realized by now,
> you can throw sighted comparison anecdotes at me until
> doomsday, but unless there's some good *independent*
> reason to believe such reports, they aren't of much use
> to me.


Understood. Ol' Arny's just raked me over the coals over in the
"Audioquest power cord" thread straightening me out over the need
for proper DBT :-) I'll never be the same...

Still, I have developed some personal techniques that I'm
comfortable with that aren't as exotic and time consuming. For
example, with a source that has two outputs, you can run both
sets of cables to your preamp and set them up so they select on
the tape loop. I can close my eyes, hit the loop button on the
remote quickly many times and then listen, guess, and then check.
Do that one or two dozen times and then swap the physical cables
(to account for differences of output/input circuitry) and repeat
the tests. It's not really a DBT since its only me but when I can
correctly pick 25 out of 25 and someone tells me I'm imagining
it, I have a problem with that :-)

Again though, I understand your target. Good luck and let us know
if you do find anything.

- Jeff
Anonymous
July 14, 2004 12:04:10 PM

Archived from groups: rec.audio.tech (More info?)

"Jeff Wiseman" <wisemanja@earthlink.net> wrote in message
news:40F4C633.CC37698D@earthlink.net

> Steven Sullivan wrote:
> <<stuff deleted>>
>> <sigh>

>> I suspect it's more likely just bad comparison techniques.
>> If they improved those, changing cables probably wouldn't
>> yield much in the way of statistically significant perceived
>> differences.

>> But I would still like to know if any *measurements*, at least,
>> have been done to verify that many two-box systems still do not do
>> clock recovery well.

I don't think that there is going to be a lot of real enthusiasm for new
tests of high end two box CD players, because for all practical purposes the
home CD player is a dead product.

Ironically, the two-box optical player as a technical concept is alive and
well. It has been reborn as a DVD player with digital output attached to a
surround-sound receiver. IME these generally work well, due to the advanced
buffering and reclocking in the receiver's DSP-based surround decoders.

> would be most interesting...

....would be beating a dead horse.

>> At what point their measurable performance
>> translates to an audible difference, is another issue.

...one that is well-treated by the well-known Benjamin and Gannon AES paper.
Cut to the chase: audible jitter in properly-designed (i.e., those that were
not gratuitously cut into two half-witted boxes by the high end in order to
increase perceived complexity and therefore revenues) was never a problem.

>> I'm sorry, Jeff, but as you might have realized by now,
>> you can throw sighted comparison anecdotes at me until
>> doomsday, but unless there's some good *independent*
>> reason to believe such reports, they aren't of much use
>> to me.

> Understood. Ol' Arny's just raked me over the coals over in the
> "Audioquest power cord" thread straightening me out over the need
> for proper DBT :-) I'll never be the same...

Hopefully...

Asking the ages-old question, can an old dog be taught new tricks.

> Still, I have developed some personal techniques that I'm
> comfortable with that aren't as exotic and time consuming.

DBTs are exotic? GMAB! They are as exotic as downloading a few files from
www.pcabx.com and listening to them.

> For example, with a source that has two outputs, you can run both
> sets of cables to your preamp and set them up so they select on
> the tape loop. I can close my eyes, hit the loop button on the
> remote quickly many times and then listen, guess, and then check.

(1) Ignores the need for level-matching
(2) Provides no assistance for time-synching which is the tough problem to
solve when comparing media players of any kind
(3) Ain't double blind.

Three strikes and you're out, Jeff!

> Do that one or two dozen times and then swap the physical cables
> (to account for differences of output/input circuitry) and repeat
> the tests. It's not really a DBT since its only me but when I can
> correctly pick 25 out of 25 and someone tells me I'm imagining
> it, I have a problem with that :-)

A total waste of time and effort.

> Again though, I understand your target. Good luck and let us know
> if you do find anything.

Or for more fun, let's start worrying about something that really matters
like recording, speakers, and rooms.
Anonymous
July 14, 2004 9:16:20 PM

Archived from groups: rec.audio.tech (More info?)

Arny Krueger wrote:
>
> "Jeff Wiseman" <wisemanja@earthlink.net> wrote in message
> news:40F4C633.CC37698D@earthlink.net
>
> > Steven Sullivan wrote:
> >> I'm sorry, Jeff, but as you might have realized by now,
> >> you can throw sighted comparison anecdotes at me until
> >> doomsday, but unless there's some good *independent*
> >> reason to believe such reports, they aren't of much use
> >> to me.
>
> > Understood. Ol' Arny's just raked me over the coals over in the
> > "Audioquest power cord" thread straightening me out over the need
> > for proper DBT :-) I'll never be the same...
>
> Hopefully...
>
> Asking the ages-old question, can an old dog be taught new tricks.


I would sure like to think so. How old are you Arny? You recently
admitted in another thread as being bald, is that from age or
just from tearing it out over some of the rec.audio discussions? :-)


> > Still, I have developed some personal techniques that I'm
> > comfortable with that aren't as exotic and time consuming.
>
> DBTs are exotic? GMAB! They are as exotic as downloading a few files from
> www.pcabx.com and listening to them.


Exotic is relative, isn't it? For the average joe listening to
different speakers at the audio store to decide which ones to
buy, the complication of setting things up for DBT would be kind
of exotic, wouldn't it?


> > For example, with a source that has two outputs, you can run both
> > sets of cables to your preamp and set them up so they select on
> > the tape loop. I can close my eyes, hit the loop button on the
> > remote quickly many times and then listen, guess, and then check.
>
> (1) Ignores the need for level-matching


True, but the gain differences between the preamp sections is
minor enough for many practical purposes.


> (2) Provides no assistance for time-synching which is the tough problem to
> solve when comparing media players of any kind


Again quite true. However, if I don't hear any difference that's
obvious, I'll make my purchase based on cost or looks of the equipment.


> (3) Ain't double blind.


'Course it is. My eyes are closed and there is no-one else in the
room! :-)


> Three strikes and you're out, Jeff!


Arny, be nice to me, I'm a sensitive type of guy! Out of your
league, yes I admit it :-) but I think it's more because my goals
may be different from yours. My intent is to build the nicest (to
me only) sounding system for as little money as I can.
Unfortunately, I don't have the funds to build a system that
really sounds like what I want anyway, so it's always a
compromise. If an item doesn't provide a significant enough
improvement for me, I can't justify trying to raise the funds for
it. Those types of differences would not normally require me to
use very sensitive test methods. In fact, I've changed components
in the past where the new one sounded just like the old except
the new one matched my wife's decore better. That's OK for me
because that's where I wanted to spend my money at the time.

Now, on the other hand, I do also have an interest in some of the
more subtle improvements that I may make from time to time. When
I start this again, I will be coming back here to get your
suggestions on practical ways to accomplish this without
short-circuiting my own efforts. Don't let me down! :-)

BTW, I used to work in the Telecom industry (in fact, I sat in
the cubicle right next to one of RAHE's moderators. He's going
bald too you know...) I lost my job quite a while back and have
been forced to sell all of my audio equipment. The only real
thing I have left is a pair of Hales Rev 1 speakers. Everything
else I have has something wrong with it where I can't afford to
fix it in order to sell it (so at least I've been justified in
keeping those items). Anyway, it's going to be quite a while
before I can get back to doing these types of comparisons so I'm
quite looking forward to it.


> > Do that one or two dozen times and then swap the physical cables
> > (to account for differences of output/input circuitry) and repeat
> > the tests. It's not really a DBT since its only me but when I can
> > correctly pick 25 out of 25 and someone tells me I'm imagining
> > it, I have a problem with that :-)
>
> A total waste of time and effort.


True ONLY if your goal is to PROVE that the differences exist.
Again, that is not my goal. It is to only help me determine what
I like. Even if it is only a preconceived psychological
difference, for my intents and purposes, I'm happy with it.

When I reach the point that I can continue to explore the
differences in comparing techniques (which I do plan on exploring
once I again have the facilities to do so) I plan to personally
do some comparisons using both DBT and the less involved
techniques I've used in the past. I want to prove to myself that
the methods I've always used are "A total waste of time and
effort" as you so clearly put it :-) I'm guessing that they will
still prove to hold value in some applications, but I will
reserve judgement on that until I am able see for myself.

- Jeff
Anonymous
July 14, 2004 9:16:21 PM

Archived from groups: rec.audio.tech (More info?)

"Jeff Wiseman" <wisemanja@earthlink.net> wrote in message
news:40F569E6.B7C54FEE@earthlink.net
> Arny Krueger wrote:
>>
>> "Jeff Wiseman" <wisemanja@earthlink.net> wrote in message
>> news:40F4C633.CC37698D@earthlink.net
>>
>>> Steven Sullivan wrote:
>>>> I'm sorry, Jeff, but as you might have realized by now,
>>>> you can throw sighted comparison anecdotes at me until
>>>> doomsday, but unless there's some good *independent*
>>>> reason to believe such reports, they aren't of much use
>>>> to me.
>>
>>> Understood. Ol' Arny's just raked me over the coals over in the
>>> "Audioquest power cord" thread straightening me out over the need
>>> for proper DBT :-) I'll never be the same...
>>
>> Hopefully...
>>
>> Asking the ages-old question, can an old dog be taught new tricks.

> I would sure like to think so. How old are you Arny?

A little shy of 60.

>You recently
> admitted in another thread as being bald, is that from age or
> just from tearing it out over some of the rec.audio discussions? :-)

Male pattern baldness is due to excess testosterone affecting the hair
follicles.

>>> Still, I have developed some personal techniques that I'm
>>> comfortable with that aren't as exotic and time consuming.

>> DBTs are exotic? GMAB! They are as exotic as downloading a few
>> files from www.pcabx.com and listening to them.

> Exotic is relative, isn't it? For the average joe listening to
> different speakers at the audio store to decide which ones to
> buy, the complication of setting things up for DBT would be kind
> of exotic, wouldn't it?

DBTs are difficult to use for comparing speakers because the differences due
to the speaker's inability to be co-located, are large compared to the small
differences that can be readily heard in a DBT. For this reason among
others, auditioning speakers in an audio store is almost universally a bad
idea.

>>> For example, with a source that has two outputs, you can run both
>>> sets of cables to your preamp and set them up so they select on
>>> the tape loop. I can close my eyes, hit the loop button on the
>>> remote quickly many times and then listen, guess, and then check.

>> (1) Ignores the need for level-matching

> True, but the gain differences between the preamp sections is
> minor enough for many practical purposes.

Absolutely wrong. Preamps have volume controls with a large range of
adjustments, and they are highly unlikely to have their settings matched
closely enough unless done using test equipment.


>> (2) Provides no assistance for time-synching which is the tough
>> problem to solve when comparing media players of any kind

> Again quite true. However, if I don't hear any difference that's
> obvious, I'll make my purchase based on cost or looks of the
> equipment.

Unless you address this problem, the difference will be so obvious that it
swamps all other possible differences. Hey, if there is a difference it sure
would be nice to hear it!

>> (3) Ain't double blind.

> 'Course it is. My eyes are closed and there is no-one else in the
> room! :-)

yawn.

>> Three strikes and you're out, Jeff!

> Arny, be nice to me, I'm a sensitive type of guy! Out of your
> league, yes I admit it :-) but I think it's more because my goals
> may be different from yours.

So its your goal to do an invalid listening test where uncontrolled (and
often random) influences dictate the outcome of the so-called test?

>My intent is to build the nicest (to
> me only) sounding system for as little money as I can.

Then forget listening tests at all.

> Unfortunately, I don't have the funds to build a system that
> really sounds like what I want anyway, so it's always a
> compromise.

One of the things most people find out from DBTs is that with many kinds of
components, reasonble expense need not force any kind of compromise at all.

>If an item doesn't provide a significant enough
> improvement for me, I can't justify trying to raise the funds for
> it.

I submit that most of the *improvements* you have heard in your life were
caused by the kind of random or bias-caused influences that I've been
talking about.

>Those types of differences would not normally require me to
> use very sensitive test methods.

But Jeff, you've been using test methods that are arguably randomized or
highly influenced by your beliefs, not actual sound quality.

>n fact, I've changed components
> in the past where the new one sounded just like the old except
> the new one matched my wife's decore better. That's OK for me
> because that's where I wanted to spend my money at the time.

If your tests are highly influenced by random influences and your personal
beliefs, how can you know that anything sounds the same?

> Now, on the other hand, I do also have an interest in some of the
> more subtle improvements that I may make from time to time. When
> I start this again, I will be coming back here to get your
> suggestions on practical ways to accomplish this without
> short-circuiting my own efforts. Don't let me down! :-)

At this time you can probably learn quite a bit *on the cheap* at
www.pcabx.com .


> BTW, I used to work in the Telecom industry (in fact, I sat in
> the cubicle right next to one of RAHE's moderators. He's going
> bald too you know...)

Don't get me started about RAHE moderators.

> I lost my job quite a while back and have
> been forced to sell all of my audio equipment. The only real
> thing I have left is a pair of Hales Rev 1 speakers. Everything
> else I have has something wrong with it where I can't afford to
> fix it in order to sell it (so at least I've been justified in
> keeping those items). Anyway, it's going to be quite a while
> before I can get back to doing these types of comparisons so I'm
> quite looking forward to it.

I'm sorry to hear about your difficulties.

>>> Do that one or two dozen times and then swap the physical cables
>>> (to account for differences of output/input circuitry) and repeat
>>> the tests. It's not really a DBT since its only me but when I can
>>> correctly pick 25 out of 25 and someone tells me I'm imagining
>>> it, I have a problem with that :-)

>> A total waste of time and effort.

> True ONLY if your goal is to PROVE that the differences exist.

No, as I've shown above, its even a waste if you want to prove that the
differences don't exist.

> Again, that is not my goal. It is to only help me determine what
> I like. Even if it is only a preconceived psychological
> difference, for my intents and purposes, I'm happy with it.

Random influences and influence based on prejudice aren't criteria that I
exactly favor.

> When I reach the point that I can continue to explore the
> differences in comparing techniques (which I do plan on exploring
> once I again have the facilities to do so) I plan to personally
> do some comparisons using both DBT and the less involved
> techniques I've used in the past.

>I want to prove to myself that
> the methods I've always used are "A total waste of time and
> effort" as you so clearly put it :-) I'm guessing that they will
> still prove to hold value in some applications, but I will
> reserve judgement on that until I am able see for myself.

Try www.pcabx.com. The price is right!
Anonymous
July 14, 2004 9:34:00 PM

Archived from groups: rec.audio.tech (More info?)

Arny Krueger <arnyk@hotpop.com> wrote:
> "Jeff Wiseman" <wisemanja@earthlink.net> wrote in message
> news:40F4C633.CC37698D@earthlink.net

> > Steven Sullivan wrote:
> > <<stuff deleted>>
> >> <sigh>

> >> I suspect it's more likely just bad comparison techniques.
> >> If they improved those, changing cables probably wouldn't
> >> yield much in the way of statistically significant perceived
> >> differences.

> >> But I would still like to know if any *measurements*, at least,
> >> have been done to verify that many two-box systems still do not do
> >> clock recovery well.

> I don't think that there is going to be a lot of real enthusiasm for new
> tests of high end two box CD players, because for all practical purposes the
> home CD player is a dead product.

I'm not even talkign about high-end two-box players -- I'm talking about
taking a sample of the now-ubiquitous DVD player-->AV receiver setups.

> Ironically, the two-box optical player as a technical concept is alive and
> well. It has been reborn as a DVD player with digital output attached to a
> surround-sound receiver. IME these generally work well, due to the advanced
> buffering and reclocking in the receiver's DSP-based surround decoders.

That's the sort of data I'd like to see. So, if that's generally true, and given that these
setups *enormously* outnumber high-end transport-->DAC CD setups in the marketplace,
should the idea that 'many two-box setups' do poorly at clock recovery continue to be
circulated, or should it be retired? How does the DVD-->AVR performance compare to a
good one-box setup when DSPs are bypassed (i.e., when using the setup for 'straight'
two-channel CD playback via the digital link?)

> > would be most interesting...

> ...would be beating a dead horse.


Not if the claim that two-box setups are inferior to one-box setups continues to
have currency. The dead horse is still alive, in audiophile-land, at least.
And it 'impugns' the vast majority of setups in existence.

> >> At what point their measurable performance
> >> translates to an audible difference, is another issue.

> ..one that is well-treated by the well-known Benjamin and Gannon AES paper.
> Cut to the chase: audible jitter in properly-designed (i.e., those that were
> not gratuitously cut into two half-witted boxes by the high end in order to
> increase perceived complexity and therefore revenues) was never a problem.

How do we know that modern commodity two-box setups (DVD-->AVR) tend to
be properly designed in that regard? What sort of measurement would one look for in the
'bench test' section of an audio magazine review to verify this?
Do you have measurement data available?

> >> to me.

> > Understood. Ol' Arny's just raked me over the coals over in the
> > "Audioquest power cord" thread straightening me out over the need
> > for proper DBT :-) I'll never be the same...

> Hopefully...

> Asking the ages-old question, can an old dog be taught new tricks.

> > Still, I have developed some personal techniques that I'm
> > comfortable with that aren't as exotic and time consuming.

> DBTs are exotic? GMAB! They are as exotic as downloading a few files from
> www.pcabx.com and listening to them.

> > For example, with a source that has two outputs, you can run both
> > sets of cables to your preamp and set them up so they select on
> > the tape loop. I can close my eyes, hit the loop button on the
> > remote quickly many times and then listen, guess, and then check.

> (1) Ignores the need for level-matching
> (2) Provides no assistance for time-synching which is the tough problem to
> solve when comparing media players of any kind
> (3) Ain't double blind.

> Three strikes and you're out, Jeff!

> > Do that one or two dozen times and then swap the physical cables
> > (to account for differences of output/input circuitry) and repeat
> > the tests. It's not really a DBT since its only me but when I can
> > correctly pick 25 out of 25 and someone tells me I'm imagining
> > it, I have a problem with that :-)

> A total waste of time and effort.

> > Again though, I understand your target. Good luck and let us know
> > if you do find anything.

> Or for more fun, let's start worrying about something that really matters
> like recording, speakers, and rooms.



--

-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
Anonymous
July 14, 2004 9:34:01 PM

Archived from groups: rec.audio.tech (More info?)

"Steven Sullivan" <ssully@panix.com> wrote in message
news:cd3qq8$skq$1@reader2.panix.com
> Arny Krueger <arnyk@hotpop.com> wrote:

> I'm not even talkign about high-end two-box players -- I'm talking
> about taking a sample of the now-ubiquitous DVD player-->AV receiver
> setups.

>> Ironically, the two-box optical player as a technical concept is
>> alive and well. It has been reborn as a DVD player with digital
>> output attached to a surround-sound receiver. IME these generally
>> work well, due to the advanced buffering and reclocking in the
>> receiver's DSP-based surround decoders.

> That's the sort of data I'd like to see. So, if that's generally
> true, and given that these setups *enormously* outnumber high-end
> transport-->DAC CD setups in the marketplace, should the idea that
> 'many two-box setups' do poorly at clock recovery continue to be
> circulated, or should it be retired?

That idea appears to be at least partially based on the poor engineering
that the concept often received when it was a high end only thing.

> How does the DVD-->AVR
> performance compare to a good one-box setup when DSPs are bypassed
> (i.e., when using the setup for 'straight' two-channel CD playback
> via the digital link?)

IME, very good.

> How do we know that modern commodity two-box setups (DVD-->AVR) tend
> to be properly designed in that regard?

We test them.

>What sort of measurement
> would one look for in the 'bench test' section of an audio magazine
> review to verify this?

Jitter resistance. Ideally, a digital signal would be pre-jittered and then
the output of the UUT would be tested for jitter.

>Do you have measurement data available?

I haven't done exhaustive testing, but the tests of DVD->DD mid fi decoder
that I have done, showed that jitter was very low in normal use, and
remained very low even when huge amounts of jitter were added to the
digital data stream coming into the DD decoder.

The UUT was earlier tested with the results posted at
http://www.pcavtech.com/adc-dac/shac300/index.htm . Even with huge amounts
of jitter added to the input stream in a later test, the results were the
same as shown in the earlier test. I believe that the SHAC300 was based on
the surround decoder circuitry in Technics contemporaneous surround sound
receivers.
Anonymous
July 14, 2004 11:42:00 PM

Archived from groups: rec.audio.tech (More info?)

Arny Krueger <arnyk@hotpop.com> wrote:
> "Steven Sullivan" <ssully@panix.com> wrote in message

> I haven't done exhaustive testing, but the tests of DVD->DD mid fi decoder
> that I have done, showed that jitter was very low in normal use, and
> remained very low even when huge amounts of jitter were added to the
> digital data stream coming into the DD decoder.

> The UUT was earlier tested with the results posted at
> http://www.pcavtech.com/adc-dac/shac300/index.htm . Even with huge amounts
> of jitter added to the input stream in a later test, the results were the
> same as shown in the earlier test. I believe that the SHAC300 was based on
> the surround decoder circuitry in Technics contemporaneous surround sound
> receivers.



Thanks!


--

-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
May 15, 2014 4:44:16 AM

Jezza said:
Archived from groups: rec.audio.tech (More info?)

I was told that burning audio CDs at slower speeds is somehow better
and produces more reliable recordings- is there any truth to this?


It has been my experience, particularly considering that manufacturers like to cut corners, that high-speed burns can be very unreliable, often only readable in the drive that burned them. I was given a database that spanned 30 DVDs burned at 22*. Every disc failed at 15% of copying and I had to lug hardware to the site to do a network copy instead.

There are numerous Region Blockers out there for reading "foreign" discs, but I've yet to find a utility that can slow down the burn speed without interfering with the drive's BIOS. If your burning software has a verify function, use it!

!