diyAudio Forums Archive - Why does CD sound better copied?

diyAudio Forums Archive > Top > Source > Digital

Pages: [1] 2

Why does CD sound better copied? - Click HERE for Original Thread

Gabevee

Hello all,

Now... I must say that I am a computer professional by trade. So I am totally taken aback by this interesting phenomenon.

As you all well know, data is data and bits are bits and unless the code for recreating the analog from the digital has undergone changes, all else being equal the sound of my CD's should be the same when I copy it to another disc. However, I have experienced that when I burn a copy of a CD (and I have done this four times) the sound of the newly burned CD is very noticably better than the original.

I hear more details, more music, more solid bass (notes are more individual), warmer voice, clearer highs.

I would like to believe that the new disc has "deeper pits" with less ringing or less "jitter" (a very moot point since stability is very superior these days) or less whatever. To me, again, data is data and once it is read into memory those other "problems" are nonexistent. And I am 100% sure that the data does not go through the A/D conversion, so that the sound can undergo the analog modifications of better analog devices.

I am burning my CDs on a Compaq laptop running W2K, using Roxio's CD Copier, with a TEAC burner, just in case this matters. I play them throguh a Sony auto stereo deck through a highly modified power amplifier. I have listened to these CDs for at least 1.5 years before copying them. I even hear a difference on the computers sound system (I have a pair of amplified speakers. Sound is pleasant enough).

So... what then is it????????

Thanks all in advance,
Gabe:confused:

Peter Daniel

I listen to the copies on my main system and I don't think they are better. It seems like they are more compressed and they don't have high frequency extention of the originals.

Last two years I made probably 500 copies. For me it's the only way to get new music.

There was other thread dealing with that http://www.diyaudio.com/forums/show...=&threadid=2341

Leo V

My copied CDs also sound better, for a simple reason. The originals were scratched and the CD player obviously couldn't retrieve up all the data. However, when I used Exact Audio Copy along with Plextor's CD burner to read the contents of the CD, it would re-read every suspicious position and retrieve almost everything possible. (CD burners tend to read scatched CDs much better than any CD-ROM or CD player, in my experience.) Thus, the CD copy had almost all of the original data, and it could be read 100% unlike the original.
--Leo

PS: I should add that I'm using high-quality Ricoh media, not el-cheapo CDR spindles.

nar

In my opinion a copy is not like to sound better than the original.But sound is different;a litlle more vulgar,so prehaps yes big bass and presence of treble,too much I think.

In fact seems to be less liquid and loose the charm of analog (that your ears feel)...

Peter Daniel

I'm using Pioneer CD Recorder PDR 509. It's not compatible with computer CD-Rs and I have to use CD-Rs for audio. They are 3 times more expensive than the regular ones, but I always thought that this is a better way to copy CDs (especially when using good transport).

Wombat

alfsch has done some tests here:

http://www.diyaudio.com/forums/show...hlight=verbatim

Wombat

LaMa

I've also some good experiences with exact audio copy. I would say try it folks because it's freeware :) (for private usage)http://www.exactaudiocopy.de/ So the question is what makes the better copy, one made with a computer cd-r drive or a copy which is made with an audio cd recorder?

Peter Daniel

quote:

Originally posted by LaMa
So the question is what makes the better copy, one made with a computer cd-r drive or a copy which is made with an audio cd recorder?

I guess you will have an answer pretty soon as I'm making copies for comparison.;)

Wombat

With a properly set up Exactaudiocopy and a good reader you will
get Bit-perfect copies, i think it will be superior to an Audio
recorder due to its error recovery. An Audio Recorder won´t try
to correct an suspicious part as long as EAC, cause the stream
would broke. I use an Asus 50x as reader.
I only heard really bad sound when i copied to Bestmedia CDRs.
Since then i use black Intenso and had no problem since. I only
burn 2x speed with my Teac 512EB.

Wombat

Gabevee

OK,

Sorry I seem to have posted a repeat subjct, I did a search but couldn't find that reference. I guess I used a different wording.

At any rate... I like what I hear. More detail, less harsh high end. Better defined bass, not overbearing bass.

I tend to doubt the jitter thing because in the early 80's I used to align hard drives and jitter, once it was aligned, was very stable. That with "discrete" technology. That is, there were five boards with gates, regulators, buffers and processors, versus the one chip with everything.

With today's LSI technology, laser trimmed quartz crystal timing, etc. Jitter shouldn't even be thought of, let alone the error correction etc. Also, I would think that in a computer, the switching power supply would reak havok in everything, especially the very delicate programming in memory (ever zap the old computers with static electricity from your fingers?) and processor chip. So.. that said... It is fascinating.

Also, I copied a couple of brand spanking new disks just to avoid that possibility. So there goes the scratched up CD theory.

Now, the compression factor may be what it is. But... wouldn't that be a change in algorythm?

Weird.

Thanks for the input!
Gabe

gigatron

I'm not sure if this is related but certain cds have copy protections they distort the actual audio... not entirely certain how certain programs copy afterwards though.

Cobra2

Hi, Peter!

Seen this?

http://www.ue-consult.de/ue_cdr.htm

Regards

Arne K
NORWAY

Peter Daniel

Cobra,

Interesting link. I would be more interested in circuit that allows make copies from a copie, since I have a big collection on DATs.

I did a computer copy of a disk using Toshiba drive, recorded on Matsushita drive, using Nero 5.

The copy sounds different and I might be biased, but for my ears the original has more microdynamics and 3 dimentionality. The midreange is better defined, while a copy produces more laid back presentation with softened treble. I didn't see any difference in bass.

Overall, however, not bad and I had some trouble deciding which one sounds better. Considering that my drives are pretty cheap and the blank disk is average quality, not bad again.

I'm gonna do more copies using same blank disk for both computer and Pioneer audio burner.

I downloaded Exact Copy, but the interface seems to be not clear. What do I have to do to make a copy?:confused:

Wombat

Here are some tutorials:

http://www.ping.be/satcp/tutorials.htm

In general you don´t copy directly. You extract the tracks to HD,
create a Cue-Sheet with all Gap infos and then burn the tracks back
with the Cue info. I always add CD-Text into this process.

Most important is to set up the reading drive correctly.

Wombat

Peter Daniel

Wouldn't copying "on the fly", omitting hard drive be better? That's what I always do.

Wombat

This doesn´t work as EAC needs time to correct small
scratches. The datastream would cut.

Omitting the HD brings nothing. The data must be delivered to the
Cashe-Ram of the burner, it doesn´t matter what source.

You can copy a CD to HD to CD to HD and the music itself is
always Bit identical. The only hearable effect brings the accuracy
of the burner and the CDR media. So choosing good medias and a good
burner is very important. Also slower writing speeds increase the
quality.

Wombat

Wombat

Something to the headline of this thread.

Todays quality of CD-Burners is better than 10 years
ago some masters for CD production.
So copying an old CD to a CDR may improve over the original.

As todays masters are from superior quality you hardly will reach
the quality with any burner.

Wombat

Peter Daniel

I remember when in the beginning of '90s Pioneer introuduced first CD audio recorder and blanks cost $20. The Stereophile reviewers claimed that copies sounded better. Since paying $20 for blank CD didn't make sense I bought Sony portable DAT. At that time I didn't hear any difference in sound quality between original disk and DAT tape copy.

Today, after reading previous claims I thought that maybe I'm not doing everything right and computer copies sound better indeed. So I did both. My computer copy listening impressions I posted already and here is my opinion on Pioneer audio burner.

I used Fuji CD-R Audio blank. The copy is closer to original then computer copy. Actually everything is the same, except the highs. There is some degradation or softening of trebles, they are not razor sharp like the original, but slightly dull.

Please note, that my comparisons were not done on car stereo, or computer, but on a top notch transport ( CD_PRO ) and a processor based on parallel Burr Brown 1704 DACs, with almost any tweak possible.;)

Wombat

I know your impressing system, half of the forum is full of it!

But this is very interesting.

Could you waste another CDR and burn it at single speed?
The Audio Recorder only writes single speed also if i´m right.

Would be very interesting if you could here different writing speeds with your burner.

Wombat

Peter Daniel

I always record with single speed. If you e-mail me your address I can send you both copies for comparison.;)

mrfeedback

I have tried copying an original audio cd to a 'black' cdr disc (black looking disc just like an original playstation game disc) and I reckon it sounds a little calmer than the original on my cd players.
Peter, I have heard a multi-track master tape of a local high profile band in three modes.
Mixed down to two tracks through the desk and fed to monitors and at the same time fed to a PC cd-burner and a dat recorder.
Neither of the copies had much of the life and air of the live mix down, with the dat copy coming in third place.
This was most illuminating (and disturbing) to hear the differences and damage that digital recording record/playback does WRT the original multitrack.
Missing was microdynamics, life, air and pleasant and extended highs.

Eric.

Leo V

Exact Audio Copy should be run in "Secure" mode to actually look for errors. To my surprise, error correction was invoked (you can watch it happen in EAC secure mode) even on shiny new CDs--and this was using my Plextor. Using lesser CD readers, I bet many new CDs would invoke error correction quite a bit more.
--Leo

Peter Daniel

I only copy brand new and shiny CDs. It would be interesting how many error corrections are invoked while making copies from EAC copied CDs.

My impression was the same as Eric's:

"Missing was microdynamics, life, air and pleasant and extended highs."

Wombat

No, Peter you don´t have to send me. I believe every word of you.

So what we know for sure is that your Matsushita recorded CDRs,
with this brand and Nero 5 sounds worse than a copy in your Audio
recorder. Both not as good as the original.

Wombat

navin

I made 2 copis of some of the CDs I have.

one copy made using my Marantz CD R (DR 6000) using TDK Audio CDR.
one copy made using HP 8250i CDR on my desktop using Maxell computer CDR.

Both CDRs were bough in spindles from Frys.

The computer copy was made using one drive (I only have a CDR on the desktop no CD reader). The Audio CD copy was made using a Phonosophie CD player.

both copies were then heard via 3 systems. one is my home made system, the other is my brother in law's system. Both systems are quite good (I can provide details if needed but that is another thread) the 3rd system was a Creative speaker 3 piece speaker system used with my desktop.

result?

There were slight differences between the Audio CD copy and computer CD copy on the 2 audio systems - the Audio CD copies were better. Not much. On the computer audio system (Creative) the computer copy sounded better! It must got to do with what each system was expecting.

The Audio copies sounded a bit dull on the computer system. The computer copies sounded a bit harsh on the Audio system. Both copies did not have as much air as the orignal but the Audio copies on the Audio systems were very close.

If you ask me I will stick to making copies using my Audio CD recorder for 2 reasons. 1. I bought one. 2. it is simpler. My nephew and BIL use their computers to make copies. I find nothing wrong with that their copies cost 1/3 mine and they get 80% of the sound. Not a bad trade off.

Cheers.

janneman

quote:

Originally posted by Leo V
Exact Audio Copy should be run in "Secure" mode to actually look for errors. To my surprise, error correction was invoked (you can watch it happen in EAC secure mode) even on shiny new CDs--and this was using my Plextor. Using lesser CD readers, I bet many new CDs would invoke error correction quite a bit more.
--Leo

I would be very surprised if error correction *was not* invoked! Error correction makes CD technology possible. Note that error correction produces an exact copy of the original and cannot be a cause of difference in sound.

There is also a thing called 'error concealment', which *will* cause differences between original and copy, which then may account for sound differences. Error concealment is quite rare, and would indicate serious problems either on the replay or on the recording side.

Jan Didden

Edwin Dorre

quote:

Originally posted by Peter Daniel

Last two years I made probably 500 copies. For me it's the only way to get new music.

I am a bit shocked.... Can you please explain me your above statement a bit???

Edwin

Leo V

What I meant by error correction was EAC re-reading a position on the CD many times in some places, because it had difficulty retrieving the correct information. My implication was that, if EAC has trouble reading these parts, then a CD player would probably have at least as much trouble. Except the CD player wouldn't go back and re-read, rather it would "fill in the blanks" at a cost to sound quality.
--Leo

Christer

quote:

Originally posted by Peter Daniel
I'm using Pioneer CD Recorder PDR 509. It's not compatible with computer CD-Rs and I have to use CD-Rs for audio. They are 3 times more expensive than the regular ones, but I always thought that this is a better way to copy CDs (especially when using good transport).

I am not sure if you mean to make any claims about media differences,
but it might be appropriate to point out a common misconception
about Audio CDR. Many people think they are better than other
CDRs for recording music, and salesmen usually claim that.
Although there might be certain brands that have better quality
on their Audio CDRs this is not generally true. The only reason
there are special Audio CDRs is that in the US there is a tax on
Audio CDRs but not on computer CDRs. An audio CD REcorder
will refuse to record or play a CDR unless it contains a special
code, indicating that it is an Audio CDR with prepaid tax. Audio
CDR have this code already from factory, while a computer
CD recorder will add that code to the media when it writes a
CDR for audio usage. According to Kodak there is no difference
in the actual media between their Audio Gold and their Ultima.
It is even recommended not to use Audio Gold if recording music
on a computer, where Ultima is labelled as excellent instead.

You might compare the media at
http://www.kodak.com/US/en/digital/...h/compare.jhtml

Although the info is still on the web, Kodak has unfortunately
stopped producing CDR as far as I know.

Now, back to Peters post. There could of course still be
differences between recording on an audio recorder and
a computer one, even if it does not depend on the media.
An audio recorder is probably of higher quality, less susceptible
to vibrations etc. A computer recorder (most of them) live its
live in an envoronment that is full of electric noise, vibrations
from hard disk and fans etc.

janneman

quote:

Originally posted by Leo V
What I meant by error correction was EAC re-reading a position on the CD many times in some places, because it had difficulty retrieving the correct information. My implication was that, if EAC has trouble reading these parts, then a CD player would probably have at least as much trouble. Except the CD player wouldn't go back and re-read, rather it would "fill in the blanks" at a cost to sound quality.
--Leo

Again, error correction doesnot 'fill in the blanks', but provides an exact copy without a single bit in error.
Error concealment does fill in the blanks.
In your case of repeated reading, there is a serious problem, and this should be very rare with correctly functioning equipment, and should be blamed on the source disk. Obviously, with a grossly defect source you cannot expect a good copy.

Jan Didden

peranders

quote:

Originally posted by Gabevee
Hello all,

Now... I must say that I am a computer professional by trade. So I am totally taken aback by this interesting phenomenon.....

So... what then is it????????

Thanks all in advance,
Gabe:confused:

Gabe, if your burner can make perfect CD's (let's asume that), ask a friend to shift the CD's for you, then have a blind test. I'm sure that you can't hear a difference (my point of view). Can you pick the burned CD with more than 70-90% right, then it's probely true. My point of view here is that the mind is very strong. My mind also....

:wiz:

Edit:
Try to get two CD players (of the same kind) also if possible.

Peter Daniel

quote:

Originally posted by Edwin Dorre

I am a bit shocked.... Can you please explain me your above statement a bit???

Edwin

I'm a pirate.:Pirate: ;)

I had to figure out some ways to reduce my spending, if I wanted to stay in DIY Audio full time.;)

Gabevee

Peranders,

I am very well aware of the fact of mind over... whatever. I was not expecting to hear any kind of difference at all. The burned CD should sound exactly like the original. But... other folks in the DIY group hear a difference, bad or good.

I have been pondering over it long and hard over the past couple of days. The only things I can think of that make sense are, as Peter said, compression. It is possible that higher amplitude signals have been reworked via the transfer of the data from CD to memory or hard drive buffer, then rewritten somewhat differently to the new disk. Only a true one to one copy, or as Peter said "on the fly" copy will maintain the dynamics of the original, I would think. It should anyway.

I say this because some subtle low amplitude music material seems louder, hence more audible, giving the impression of more detail.

The other thought was touched on in another post, where the question of single speed copying was brought up. I use the highest speed I can. I am going to try single speed to see if it is different.

Thanks,
Gabe

Christer

Please Gabevee, didn't you say you were a computer scientist? ;)

There is no compression at all when you copy CDs to/from the
hard disk, unless you use MP3 or other compressed formats.
Under windows the data from the CD is stored in a wave file
which is PCM coded, just as the CD data itself, and the data is
preserved. The wave files in Wndows are general enough to
handle more than 16 bits, higher sample frequencies
and more than 2 channels, should you need that. I don't know
what file formats Mac and Linux use, but I am sure they also
preserve the data.

Actually, the wave files are very nice since they are so simple.
It is quite easy to write programs that generates wave files
with various test signals that you can record on a CDR.
Similarily it is easy to collect data via the soundcard for analysis
(although the soundcard will set a limit here, of course).

Wombat

As is said before, the data itself is absolutely the same as
on the original BIT BY BIT if no read errors occure.

So the different sound only comes from the way the data is
written to CD. Lets call it the stream on the CDR is more "jittery".
So the optics in the CD-Player has more work to read it and
creates different sound this way. Noisy enviroment high writing
speeds and bad media will raise these problems.

No compression or attenuation is done to the music data!!

Wombat

edit: ups, same time postet as Christer

janneman

As said before, this line of reasoning assumes that there indeed IS a difference in sound. Unless that is established without a shadow of a doubt, all this is interesting but trivial speculation. Sorry.

Jan Didden

peranders

Also, don't forget that you really clone the audio file, EXACT copy. You can't loose any amplitude.

You can get into trouble if you burner is a little bit older and can't burn "disc at once", then you really won't get exact copies but this is only between the tracks. You can't burn with zero pause, very irritating if you have a live recording.

Gabevee

Christer,

No, not computer scientist. :( Professional.

I know much digital info, but haven't gotten into it this deeply in years. Concentrating on WAN/LAN stuff.

I am going to have to get a couple of books on the latest trends.

As for the nay sayers, one of the recordings I have copied is a Phillips recording of Beethoven's 4th and 5th piano concertos. The original disc skipped occasionally (the player would of course resume from where it left off), indicating to me a weak recording. When I copied it, no more skip. I do notice that the reflective layer was so thin on the original one could see through it, FWIW. Again, it does sound better.

Gabe

johan.vikstrom

The absolute techguy speaks (rightside of brain)

1) If a burned CB sounds different from the original, then the CD is not 'digital' the same as the original cd. This should make the copy of data cd impossible, because if the data is not as the original then the new data cd will not work.

2) As long the cd transport can read the datastream correctly there can be no audiable change from the original cd.

3) The 'bitstream' from the CD is kinda timebuffered from the the DAC, small differeance in lenght in 'one' and 'zeros' will not alter the sound produced. All serial digital transports works this way.

4) A cd transport is NOT affecting the sound of the produced sound. As long the DAC is feed with correct digital stream, all digital transport will produce the 'same' sound. Again - small time errors etc will not change the work of the DAC.

5) This is the absolute truth, there is no way trick the datastream. Exception is rare products that is constructed to behave in this way, thoose products are badly designed.

6) Not a single CD tweak works (as long there is no read errors). Keeping CD in frig, painting sides green, etc. There is no effect.

The Hifiguy speak (left side of brain)

1) I have heard differences in the sound from some CD tweaks. For example, there was one guy who soaked the CD in a not static fluid.

It would be interestring to hear some tec reasons why cd tweaks shoud work. Since I have talked about this with guy who designs and constructs profensiol equipment for digitaldata streams (video, audio,data) and they claims that all chances are only in "the mind"

Christer

quote:

Originally posted by Gabevee
No, not computer scientist. :( Professional.

I know much digital info, but haven't gotten into it this deeply in years. Concentrating on WAN/LAN stuff.

I am going to have to get a couple of books on the latest trends.

OK. I hope you didn't get me wrong, though. It was only meant
as a friendly joke. BTW, I am a computer scientist, but you would
have plenty of opportunity to give back. I am not very good at
the practical matters in general. I did check up on wave file some
years ago, when I wanted to make a test CD, so that why I
know about them. Probably wouldn't have cared about them
otherwise, just using them.

Peter Daniel

quote:

Originally posted by johan.vikstrom
The absolute techguy speaks (rightside of brain)

1) If a burned CB sounds different from the original, then the CD is not 'digital' the same as the original cd. This should make the copy of data cd impossible, because if the data is not as the original then the new data cd will not work.

2) As long the cd transport can read the datastream correctly there can be no audiable change from the original cd.

3) The 'bitstream' from the CD is kinda timebuffered from the the DAC, small differeance in lenght in 'one' and 'zeros' will not alter the sound produced. All serial digital transports works this way.

4) A cd transport is NOT affecting the sound of the produced sound. As long the DAC is feed with correct digital stream, all digital transport will produce the 'same' sound. Again - small time errors etc will not change the work of the DAC.

5) This is the absolute truth, there is no way trick the datastream. Exception is rare products that is constructed to behave in this way, thoose products are badly designed.

6) Not a single CD tweak works (as long there is no read errors). Keeping CD in frig, painting sides green, etc. There is no effect.

Since I have talked about this with guy who designs and constructs profensiol equipment for digitaldata streams (video, audio,data) and they claims that all chances are only in "the mind"

If the above was true, we would be still happy with cd players made in '80s with no need to upgrade, because they were producing perfect sound forever.;)

History proves otherwise.:rolleyes:

Christer

Johan,

I do not claim there is a differencce between original and CDR
(I have only done a few experiments a long time ago) but since
many report differences, one should perhaps keep an open
mind. So let me just point out some errors in your reasoning.

quote:

A CD is not digital. It is a physical medium which is used to
encode digital data as a stream of lands and pits. These are not
perfect. There is variation in the lengt and depth profiles of these,
there is always some variation in thickness and transparency of
the transparent layer, variation i the dye layer, variations in the
reflective layer etc. A CD is an analog medium, used to store
digital data. All these factors affect how well we can record
and retireve the data from the disc. This applies also to the
original pressed CD, of course, and these are usually of low
quality compared to good CDR: the disc itself is thinner and
less stable, the reflective layer is thinner and made of aluminium.

There is a big difference between audio CDs and data CDs. An
audio CD is read in realtime and the data format is such that
you cannot reread data without rereading a whole track. A data
CD on the other hand stores the data in blocks which can be
read individually. When a read error occurs, an audio CD player
cannot reread the data, while a CDROM device will just go back
and read the block again.

quote:

2) As long the cd transport can read the datastream correctly there can be no audiable change from the original cd.

Yes, but unless we are certain that the datastream is read
correctly, this could be an explanation for differences in sound.

quote:

3) The 'bitstream' from the CD is kinda timebuffered from the the DAC, small differeance in lenght in 'one' and 'zeros' will not alter the sound produced. All serial digital transports works this way.

I am not quite sure how CD players usually work, but presumably
there must be some kind of PLL to synchronise the read clock
with the noisy analog signal from the laser. So I suppose
variations both in the recorded data and the speed of CD player
could affect the bit error rate. After clocking the data, there
should be no effect, assuming a sound digital design.

johan.vikstrom

quote:

Originally posted by Peter Daniel

If the above was true, we would be still happy with cd players made in '80s with no need to upgrade, because they were producing perfect sound forever.;)

History proves otherwise.:rolleyes:

Yupp (half true)

A cd is read with a laser, the signal is decoded and a 'bitstream' is sent to a DAC.

The DAC (digital audi converter) has imporves alot since '80. That is the what you and other hears :)

The digital reading and sending of the bitstream is of less importance since a zero or a one can only be that, there is nothing like a bad "zero". If the signal is to distored a error will occure.

Any correction to the quality of the sound should be done on the DAC or after.

peranders

quote:

Originally posted by Peter Daniel
If the above was true, we would be still happy with cd players made in '80s with no need to upgrade, because they were producing perfect sound forever.;)

History proves otherwise.:rolleyes:

You know, some CD drives have become better but my old and slow Denon DC-1500 plays damaged CD's excellent because of the slowness. Faster drives get nervous when they see a real big gap in the data. But I don't deny that the DAC is a little bit old. The machine has LC-filters, YES.

Peter Daniel

I also like my older transports (Technics Z-1000 and Marantz CD-94) and Sony although not as refined as the other two, playes any disk withut problem. The DACs though, need serious upgrading.

johan.vikstrom

quote:

Originally posted by Christer
Johan,

I do not claim there is a differencce between original and CDR
(I have only done a few experiments a long time ago) but since
many report differences, one should perhaps keep an open
mind. So let me just point out some errors in your reasoning.

Yes, I'm open and I belive that i perhaps will find a difference in the sound. What it depends on is the most important part.

quote:

Correct, but a good DAC will show errors in the bitstream. Since souch error is very rare, the reading of the CD can't be of any importance. If the data is read correctly then it's up to the DAC to make sound of it.

Since the DAC runs on a separate clock all the CD (and transport) need to do is to feed enough data to the DAC. Remember that digitals streams zero and ones is by definition allowed to flux in length.

If there is read or conversions error in the process there will changes in the sound, but I can't belive that CD players are of so low quality.

quote:

I belive that the early part of the decoding of the CD is of low importance.

The last and most important clocking is done in the DAC and when the analog signal is created. Before that there is also a clocking but that clock is allowed a flux.

conclusion.. (do you agree?)

If there is problem for the cd and electionics to read the cd there can be a differance when you copy a CD.

Is it possible that CD players are so bad that they cause read error, that each time you play a CD it will sound slightly different.

johan.vikstrom

quote:

Originally posted by Peter Daniel
I also like my older transports (Technics Z-1000 and Marantz CD-94) and Sony although not as refined as the other two, playes any disk withut problem. The DACs though, need serious upgrading.

Yeahh, I agree.

The cost has probably forced the manufactors to cut some mechanical good designs. Forced them to use less plastics, and perhaps even go without metal parts, only to cut some cost.

Peter Daniel

quote:

Originally posted by johan.vikstrom

Yupp (half true)

A cd is read with a laser, the signal is decoded and a 'bitstream' is sent to a DAC.

The DAC (digital audi converter) has imporves alot since '80. That is the what you and other hears :)

The digital reading and sending of the bitstream is of less importance since a zero or a one can only be that, there is nothing like a bad "zero". If the signal is to distored a error will occure.

Any correction to the quality of the sound should be done on the DAC or after.

Did you ever tried to buitd CD transport yourself? I did and can assure you that it has the same importance as DAC, if not bigger.;)

UrSv

Maybe it is a little misleading to say that the burned CD sound better than the original or the other way round. It is the player sounding different playing the variations I would say. I have read various explanations to this preposterous/actual fact and reasons for differences either way may be:

CD-Rs have different reflection properties than original CDs. Less/More precise reading - Less/More error correction - Less/More jitter - Less/More spurious reflections.

CD-Rs have (or so I hear) a different topology (grooves/no grooves) compared to standard CDs with different tracking/auto-focus properties for the player. See previous results.

CD-Rs could be better centered than burned. Standard CDs may be slightly off-center (but oh so slightly). See previous results.

Please also note that many claim to hear differences between recording speeds. Slow copy it seems give the best result. Today copying at 40+ speeds is a perfect data copy but possibly not a perfect audiophile copy. Try a single speed copy and compare it with a 16 speed copy for instance.

Myself? ALL copies I had (Yes, had I don't have single copy left) sound dull and laid back. Didn't like them at all as a matter of fact. Possible need for new computer gear identified - darn...

/UrSv

PS. johan.vikstrom. Are you confusing these things to be ideal compnents (no offense intended)? My stuf is real world gear and they work not quite according to marketing descriptions...

Christer

Johan,

Yes the crucial question is the one about read errors. Read
errors do occur. The question is how often non-correctable
read errors occur. We had a discussion on this a couple of days
back in the thread about blue lasers. I was told many years
ago in a HiFi-shop nearby that they had done experiments on
their best CD player (this might have been 15 years ago),
connecting a frequency counter to the signal indicating read
errors and got quite a high frequency. On the other hand
Steve Eddy said that he and some friends had done a similar
experiment on a number of different players and found that
the non-correctable read errors were extremely rare. It could
be that the people I spoke to had actually measured all
read errors, including the correctable ones. Both I and some
of my friends have seen a tendency that CD players of rigid
mechanical build tend to sound better. Perhaps it is just
coincidence, otherwise I suspect it must have to do with
read errors.

johan.vikstrom

quote:

Originally posted by Peter Daniel

Did you ever tried to buitd CD transport yourself? I did and can assure you that it has the same importance as DAC, if not bigger.;)

Nupe, never built a CD transport.

Is it not like this..

If the signal to the DAC is withour digital errors then the transport does the work good enough ?

My DAC is costing 30k$ so I did some serious visits to resellers to check nice CD transports before I decided that I could remove my CD and go for a DVD as CD transport. There was not possible to hear any difference when I tried a transport for 30k$ and a DVD for far less.

Perhaps I'm wrong, but I wish that someone can prove how a CD transport can improve my system. (that is the main goal- to improve my system).

Blind test has so far failed, perhaps I did get unlucky and runned into expensive but bad transports.

chris ma

quote:

Is it possible that CD players are so bad that they cause read error, that each time you play a CD it will sound slightly different.

Actually this is exactly I am experiencing, but the deteriation is very subtle, it takes a couple of days for the difference to get noticed, then I used the Bedini Ultra Clarifier to treat the CD and everything back to normal and the process repeat with the same CD, especially after the CD has been used in my car, then I notice the deteriation right away when play the CD in the house.

But how come no body mention (ditther/ditter don't know the spelling of the word) when we are talking about the digital 0 and 1 wave form and convert to analog sino wave forms?
:confused:

Peter Daniel

quote:

Originally posted by johan.vikstrom

My DAC is costing 30k$ so I did some serious visits to resellers to check nice CD transports before I decided that I could remove my CD and go for a DVD as CD transport. There was not possible to hear any difference when I tried a transport for 30k$ and a DVD for far less.

You must be seriously joking.;) ;) ;) ;)

If you really had 30k$ DAC you wouldn't write any of the nonsense you just did in this thread.;) ;) ;) ;)

johan.vikstrom

quote:

Originally posted by Christer
Johan,

Yes the crucial question is the one about read errors. Read
errors do occur. The question is how often non-correctable
read errors occur. We had a discussion on this a couple of days
back in the thread about blue lasers. I was told many years
ago in a HiFi-shop nearby that they had done experiments on
their best CD player (this might have been 15 years ago),
connecting a frequency counter to the signal indicating read
errors and got quite a high frequency. On the other hand
Steve Eddy said that he and some friends had done a similar
experiment on a number of different players and found that
the non-correctable read errors were extremely rare. It could
be that the people I spoke to had actually measured all
read errors, including the correctable ones. Both I and some
of my friends have seen a tendency that CD players of rigid
mechanical build tend to sound better. Perhaps it is just
coincidence, otherwise I suspect it must have to do with
read errors.

This is interesting, because my DAC shows errors feed to it from the source. The errors from a CD are very rare, from a digital sat reciver the errors are more common.

I must admit that I can't tell what errors are detected, i asume that if using PCM there is bit error that can occure. I'm not sure if that is due to signal error or if the transport sends wrong information.

Will it be possible to conenct a digital output from a CD into a digital input on a computer, and run same cd several times. Then after a few recordings, do a binary compare ?

johan.vikstrom

quote:

Originally posted by Peter Daniel

You must be seriously joking.;) ;) ;) ;)

If you really had 30k$ DAC you wouldn't write any of the nonsense you just did in this thread.;) ;) ;) ;)

Why not ?, only because i'm dumb enough to set 30k into a DAC does not mean that I can't think.

Why should I accept something that does not 'compute'.

Nobody should be happier that me if I could gain anything from improving my transports.

I do not buy the "all things can't be measured or calculated", it it was so, we should not have places a man on the moon.

Sometimes it's more easy to construct something with the ears and the feelings, but it can surely be measured and explained.

The tranpost issue has so far not been explained, unless read errors are common.

flutters are not real :)

Peter Daniel

quote:

Originally posted by johan.vikstrom

I do not buy the "all things can't be measured or calculated", it it was so, we should not have places a man on the moon.

You just said that. If you subscribe to the above point of view, the 30k$ DAC purchase would never be justified and realized.;)

johan.vikstrom

quote:

Originally posted by Peter Daniel

You just said that. If you subscribe to the above point of view, the 30k$ DAC purchase would never be justified and realized.;)

Arrrrghh.

Do not tell me such things:xeye:

It did sound nice and it did look even nicer, perhaps i could have found one found for less money, perhaps i could have been happy with a cheaper one. (it has some more functions, but it was mainly as a pure DAC i invested in it)

Peter Daniel

Hey, don't be upset, we all make mistakes.;)

Pedja

Hello,

I�m living in Serbia and regarding the original and copied cd�s that means two things:
1. last 10 years we did not have so many original discs to buy;
2. last 10 years we did not have so much money to buy original discs.
This country is overwhelmed with copied cds.

Every ordinary audiophile in this country listened a lot of copied cd�s. And spent some time evaluating its qualities. It is not easy to find here anyone who will claim improvements on copies. There are some people whose �job� is manufacture and sale of such discs, and even they rarely claim better sound of copies.

Many times I made original vs. copy A/B test. Copies were made on different burners, with different software, with different speeds, with different media, also tried �on-the-fly� copy. Still, I�m not an expert for this, but...

Neither copy was as an original. Main problems are those Peter mentioned. More compressed and less high frequency extension. And more dry and more aggressive. However, many copies are quite acceptable quality and quite listenable. Interesting, but I can not say there were differences between the readers/burners. Neither change of the speed do much of anything. On-the-fly (+ real-time copy) surely doesn�t reduce the difference between the original and the copy. The only way to influence the sound I found is usage of EAC. It makes the copy not to sound dry and aggressive, but also there is an obvious loss at the upper treble. EAC have this effect as extracting, just as the burning software.

And in whole this story, I don�t see a reason why copies couldn�t be �bit identical� to originals. Of course if you don�t make some error and cd is not damaged. How computers could work if copies couldn�t be a �bit identical�?

I just checked two wav files extracted from one audio cd. One is extracted with EAC, the second with AudioCatalyst. They are practically the same. Just a few different characters in the starts of the files. From the expirience I know the files extracted in EAC and AudioCatalyst do sound different. So, it will be very interesting to learn some day what is the point here.

Pedja

p.s.: Johan, you paid 30K$ for DAC and came to diy area? Maybe you will copy CDs because originals are expensive? ;)

johan.vikstrom

quote:

Originally posted by Pedja
Hello,

I�m living in Serbia and regarding the original and copied cd�s that means two things:
1. last 10 years we did not have so many original discs to buy;
2. last 10 years we did not have so much money to buy original discs.
This country is overwhelmed with copied cds.

Every ordinary audiophile in this country listened a lot of copied cd�s. And spent some time evaluating its qualities. It is not easy to find here anyone who will claim improvements on copies. There are some people whose �job� is manufacture and sale of such discs, and even they rarely claim better sound of copies.

Many times I made original vs. copy A/B test. Copies were made on different burners, with different software, with different speeds, with different media, also tried �on-the-fly� copy. Still, I�m not an expert for this, but...

Neither copy was as an original. Main problems are those Peter mentioned. More compressed and less high frequency extension. And more dry and more aggressive. However, many copies are quite acceptable quality and quite listenable. Interesting, but I can not say there were differences between the readers/burners. Neither change of the speed do much of anything. On-the-fly (+ real-time copy) surely doesn�t reduce the difference between the original and the copy. The only way to influence the sound I found is usage of EAC. It makes the copy not to sound dry and aggressive, but also there is an obvious loss at the upper treble. EAC have this effect as extracting, just as the burning software.

And in whole this story, I don�t see a reason why copies couldn�t be �bit identical� to originals. Of course if you don�t make some error and cd is not damaged. How computers could work if copies couldn�t be a �bit identical�?

I just checked two wav files extracted from one audio cd. One is extracted with EAC, the second with AudioCatalyst. They are practically the same. Just a few different characters in the starts of the files. From the expirience I know the files extracted in EAC and AudioCatalyst do sound different. So, it will be very interesting to learn some day what is the point here.

Pedja

Hmm, interesting - I need to find a way to tell if a burnt CD causes more read errors.

quote:

p.s.: Johan, you paid 30K$ for DAC and came to diy area? Maybe you will copy CDs because originals are expensive? ;)

Why not ?

I'm mainly interested in building loudspeakers since I do not have any tools or time to do electronics constructions.

DIY is for me more fun than to buy it from a store.

johan.vikstrom

quote:

Originally posted by Pedja
Hello,
p.s.: Johan, you paid 30K$ for DAC and came to diy area? Maybe you will copy CDs because originals are expensive? ;)

Hello Pedja.

I'm kinda strange in that way, I even have originals in my car. I do not like burnt CD's, perhaps it's that they do not have labels or nice picturures.

I do even strongly belive in that albums should have the originals songs and correct order. No making "mr nice music cd" here.

As original, and then I can buy the original instead of going through the effort to make a copy or download from internet.

DIY is for my FUN,FUN not a way to save money, In my opinion most DIY projects tends to become more expensive than to buy it from the shell (taking time into the consideration)

Peter Daniel

quote:

Originally posted by johan.vikstrom

DIY is for my FUN,FUN not a way to save money, In my opinion most DIY projects tends to become more expensive than to buy it from the shell (taking time into the consideration)

And here I finally agree with you.;)

Pedja

quote:

Take nerves also in consideration... and you're right again, it is still fun.

Pedja

Gabevee

Christer,

Of course I took it in the spirit it as meant. I was just trying to be a clown.:clown:

As for the comment on why the older CD player played bad CD's better... it is due to better error correction. Nothing more. I had a CD player made in 1983 that cost me about $250. There were others made for over $1000. Both prices were pretty high for those days. The biggest differences? Error correction and superior analog amplifier.

I bought my more recnt CD player (5 years ago) judging the choice based on an old CD that was so messed up it was unreadable by the old boy. The one I chose was only $110. They'd come a looooooong way in 13 years. And even longer in the past 6.

The only thing that made a difference in sound quaity was when I replaced the **** op-amps with good quality bifets.

Well... as with everything else in this fantastic hobby, whatever sounds best to each individual. I would still like to know why, tho.

Gabe

Wombat

Damn i have to learn to quote :(

@johan.vikstrom

You asked if it is possible to hook up a CD-Player to a PC and compare the data.

For sure it is. Many sound cards have digital in. I archived my old DAT tapes this way.

I copied a perfectly new CD that had 100% accuracy with EAC via S/PDIF into soundcard.

And guess what!? The created wavs are identical! (once you are able to synchronize the first bit to compare)

Wombat

Gabevee

To All,

Here is an interestig article:

http://www.roxio.com/en/interest/music/aboutdae.jhtml

It seems that the data is rewritten when ripped. So there may be a recreation or modification somehow. For those who get worse sound, upgrade your software (to latest version of what you have, not necessarily Roxio).

Also, this article speaks about audio only versus standard CD-R's. I use CD-Rs because I already knew better.

http://www.roxio.com/en/interest/music/audiomedia.jhtml

Gabe

Ken L

It may be a little hassle to find a compatible burner- but they should be cheap - you would need a SCSI card

I'm using Prassi CD Rep Pro 2.0 ( a professional CD Replicating program) and a Plextor R412C which should be available as a refurb or used in the North American market anyhow.

Both software and hardware are long out of production- But software can easily be made available to interested parties

Most of my burning has been Data - true images - I haven't done very much audio because I only listen at home.

But if I remember correctly the Audio CD's I made from it were bit for bit copies - I know that without question the data CD's are not distinguishable from the original - there are a few multiple mode special copy protections that cannot be copied with this program -

I'm burning a Diana Krall CD as I post this to see if it comes out bit for bit.

The point in time that the hardware software comes from (maybe about 4 or 5 years ago) there was nothing to do a true image that was not SCSI - Still very few today - there is also a good bit of confusion due to the fact that a number of programs _say_ they make an image and they do sort of - but very few make a _true_ image bit for bit.

If some here are interested, we can figure a way to distribute the software - then if you found a compatible burner - buy the scsi card if you don't have one. There are other burners that are compatible, but only SCSI.

Prassi pulled out of the US market due to lawsuit and infringement problems with Adaptec - I have some later European versions but I continue to use the older one - runs fine on Win2K Pro -

Peter, you or anyone else :Pirate: out there interested?

Ken L

PS although no longer supported by the factory - basic tech support available right here on this forum

Pio2001

Hello, I'm coming a bit late, sorry. I'd have things to say.

First, I'd like to comfirm that the data read is error free.

In digido.com, the main source of explanations (true or false) about differences in the sound of copies vs originals, they say the copies were checked to be bit exact copies of the originals.

Besides Wombat, I also ran the test of recording the SPDIF output of a CD player in the computer (you need a soundcard capable of slaving its input to the incoming SPDIF stream) : Yamaha CDX860 (450 � in 1991). Copies of a 4 minutes track with crappy digital cables, coax and optical, and copy of the same track with EAC in the computer were all identical. Not a single bit was different.

Oliver Friedman ran the test on a whole CD with a Sony CD player : there was one or two wrong samples in the copy.

Otherwise, I see nothing new in this thread, still the same story of those who say there is a difference and those who say there is not.
Personally, I think some CD player could make copies sound different, some not, but it's just my opinion.

But I'd like to know if someone hearing differences (I don't) could run an ABX blind test of at least 8 sessions.

Until someone succeeds in a blind ABX test, we're loosing our time talking for nothing. The success of such a test would prove the difference objectively once for all (well, I should say once for the CD Player and the copy tested).
It's not so difficult to run, it just takes time.

patwen

Hi, I am surprised that no one bring up the issue of "jitter".

The MAIN reason the CDR copy sounded different (usually better) than the original is because of jitter.

The CDR copy and the original is bit perfect most of the time. Means the 1's and 0's are 100% correct.

BUT the timing of the 1's and 0's are different. In other words, the exact time of arrival of the transition edges are different. This timing difference is now well known as "jitter".

If the original CD has some jitter on it (say average 200ps), and the CD writer is a good one and burnt at 2X or 4X speed (tests showed that 1X actually produce slighter higher amount of jitter usually), the CDR copy will usually has less jitter (say average 100ps) than the original, and the CDR copy WILL surely sound better than the original.

You may ask how come the original CD has so much jitter? It's not difficult at all:

http://www.audioasylum.com/audio/ge...ssages/977.html

This topic has been discuss nearly to death on audio asylum. Do a search and you will find a lot of reference.

For me, I use Yamaha 3200 CD writer which has Audio Master Quality recording fuction which reduce jitter further. I can consistantly made CDR copy as good as the original (if the original is fairly good already), OR made better copies than the original (if the original copy is only so so).

This is really a non-issue for me. BTW, I also added some bypass caps to the power supply of the yamaha writer ;) .

So it is not about "data error" at all, it about "jitter" or "timing error".:cool:

johan.vikstrom

quote:

Originally posted by patwen
Hi, I am surprised that no one bring up the issue of "jitter".

The MAIN reason the CDR copy sounded different (usually better) than the original is because of jitter.

The CDR copy and the original is bit perfect most of the time. Means the 1's and 0's are 100% correct.

BUT the timing of the 1's and 0's are different. In other words, the exact time of arrival of the transition edges are different. This timing difference is now well known as "jitter".

If the original CD has some jitter on it (say average 200ps), and the CD writer is a good one and burnt at 2X or 4X speed (tests showed that 1X actually produce slighter higher amount of jitter usually), the CDR copy will usually has less jitter (say average 100ps) than the original, and the CDR copy WILL surely sound better than the original.

You may ask how come the original CD has so much jitter? It's not difficult at all:

http://www.audioasylum.com/audio/ge...ssages/977.html

This topic has been discuss nearly to death on audio asylum. Do a search and you will find a lot of reference.

For me, I use Yamaha 3200 CD writer which has Audio Master Quality recording fuction which reduce jitter further. I can consistantly made CDR copy as good as the original (if the original is fairly good already), OR made better copies than the original (if the original copy is only so so).

This is really a non-issue for me. BTW, I also added some bypass caps to the power supply of the yamaha writer ;) .

So it is not about "data error" at all, it about "jitter" or "timing error".:cool:

After a binary datastream are feed into a DAC part the jitter does not mean anything. All digital datastreams have jitter and time fluctations, therefore all recivers of digital datastreams handle this.

A 'one bit' serial DAC can have problems with jitter, but only if it's badly designed. All DAC should and must carry their own clock.

chris ma

IMHO
If that is the case why recording studios waste so much money and promote on the high end recordings on the recording side, if the user/consumer ends on the play back side all utilize a nice clock/DAC. Then we all have good music regardless of how the recording was engineered.
;)

patwen

In theory, what you are saying is correct and it is the textbook answer and what they have tought us in school.

May I invite you take a look at Jon's excellent notes on jitter:

http://www.geocities.com/jonrisch/jitter.htm

Jitter affects the DAC from every angle possible, the data, the power, the ground etc etc;)

Quote a small part:
"...Jitter read from a CD will affect how well the read servo stays locked, and how much the read servo has irregular power supply demands. Just about everything and anything affect the power supply, so reduce jitter read from the disc, and it will affect the accuracy of the playback event..."

"By the same token, a CD with jitter added during the mastering process (or the burn of a CD-R) will cause the servo mechanism to fire in the jittered pattern, and the laser recieve optics, etc. EVERY STAGE THAT HANDLES THE SIGNAL EVEN IN DIGITAL FORM loads the PS in a particular pattern. With a clean signal, that pattern is clean, with a jittered signal, that pattern is jittered, and adds to the overall jitter of the reproduced signal. Hence, the vast majority of jitter is signal correlated, even if indirectly via the digital data stream's imperfect timing and variations."

if life can only be so simple and perfect ... :)

johan.vikstrom

quote:

Originally posted by patwen
In theory, what you are saying is correct and it is the textbook answer and what they have tought us in school.

May I invite you take a look at Jon's excellent notes on jitter:

http://www.geocities.com/jonrisch/jitter.htm

Jitter affects the DAC from every angle possible, the data, the power, the ground etc etc;)

Quote a small part:
"...Jitter read from a CD will affect how well the read servo stays locked, and how much the read servo has irregular power supply demands. Just about everything and anything affect the power supply, so reduce jitter read from the disc, and it will affect the accuracy of the playback event..."

"By the same token, a CD with jitter added during the mastering process (or the burn of a CD-R) will cause the servo mechanism to fire in the jittered pattern, and the laser recieve optics, etc. EVERY STAGE THAT HANDLES THE SIGNAL EVEN IN DIGITAL FORM loads the PS in a particular pattern. With a clean signal, that pattern is clean, with a jittered signal, that pattern is jittered, and adds to the overall jitter of the reproduced signal. Hence, the vast majority of jitter is signal correlated, even if indirectly via the digital data stream's imperfect timing and variations."

if life can only be so simple and perfect ... :)

I say..

You are completly correct :)

If the servo is forced to do more, then the load on the powersuply will be variable. That can cause distubance to the DAC.

....but

If the DAC is powered by another powersuply and that powersuply is on another outlet, can we still except the DAC to be affected by jitter ?

Pedja

quote:

Originally posted by patwen
Hi, I am surprised that no one bring up the issue of "jitter"...

... The MAIN reason the CDR copy sounded different (usually better) than the original is because of jitter...

... BUT the timing of the 1's and 0's are different. In other words, the exact time of arrival of the transition edges are different. This timing difference is now well known as "jitter"...

... If the original CD has some jitter on it (say average 200ps), and the CD writer is a good one and burnt at 2X or 4X speed (tests showed that 1X actually produce slighter higher amount of jitter usually), the CDR copy will usually has less jitter (say average 100ps) than the original, and the CDR copy WILL surely sound better than the original...

Jitter is the term that �easily� explains sound differences here, but only in the writing/burning domain. And, of course, if you understand copying as a kind of reclocking, there is the reason to be an optimist.

But there are some missing points again.

As I said there are sound differences between the extraction software. Also said two files extracted with different software are bit identical but do sound different. If jitter could explain this, it would mean the jitter�s structure can be saved inside the wav file written in the hard disc. Then, that jitter should be �preserved� in its transition to CD media (and data that are written in it). But, shouldn�t signal be analog by nature to respond to these �demands�?.

Pedja

Gabevee

One question:

Does anyone really know how the data is read from the disc? I mean, the whole process, so that they would realize that jitter is a non-issue? I deeply apologize if I sound sarcastic. I do not mean to. But we may be speaking from incorrect assumptions.

Alright, correct me if I am wrong, but:

Jitter is the result of sync problems between the various circuits of data flow starting at the platter, which has minor variations in speed. This used to be caused by heat differences in the circuits, because of them being on different chips (known as discrete circuitry). The time it takes data to travel through the wiring and circuit traces contributed to this, as well as separate clock oscillators. Now that everything is on one chip, heat is no longer a problem, nor delays in propogation or clock differences. Jitter is neglegible.

Data is read once within a "window". This is the read window. It is a certain amount of time long. Within this window the data will be read only once, no matter where within the time window the data is. I do not know for sure, but I am willing to bet the data is read on one of the transition slopes, the up or down clock, to be exact. (It is more likely read as a zero crossing. which makes the problem of jitter fade even firther back into the darkness). Once it has been detected and stored in the RAM, it is there to stay with no other interference or reads of spurious data... or noise... period, jitter notwithstanding. Hence why I say it is a non-issue. Even those who believe in the laser reflection theory of bad CD sound will have a difficult time making someone... who knows... accept it.

Even if there is noise within a window that is supposed to have a zero bit, there is that little thing known as parity (and don't forget the zero crossing thing either. Noise is usually polarized and doesn't cross the zero), as well as the error correction algorythm, that would remove anything that was there that doesn't belong. That is the program that was written back in the 70's that allows for error correction and the reassembly of the original audio content (I forget who wrote it and what it is called).

That is why I said that only a change in algorythm will cause the sound to be different, bad or good. When the data is read from your CD and placed on a hard drive (except for the instance of on the fly copying, as in a dedicated CD copier), then the data is reformatted to fill the different sized sectors (versus each word of data on the CD, plus going from stream to.. whatever it changes it to) of the hard drive. This data then has to be reconfigured back to the original state while being written back onto the CD.

And that is why the die hards will say that you need to do an ABX test several times in order to actually ascertain that there is an audible difference, because there shouldn't be a difference at all.

But this is why I asked in the first place, because I am pretty sure that there shouldn't be a difference either.. but I hear one. AAMOF, my PC at home makes exact duplicates. No sonic difference. (BTW I am using Roxio's CD copy version 5 on my desktop, and version 4 on my laptop).

Reading what I read on Roxio's site clarified why to a degree. I seem to recall reading that there have been changes in the algorythm to enhance the sonic character and quality to a small degree. If you have played with Roxio's settings when copying a CD, there is one option that asks "Do you want the volume to be the same for all tracks?", which confirms a change in algorythm, in spite of the bit by bit comparisons. So there may be some compression going on or something. But not jitter.

Gabe

patwen

May I invite everyone who think "jitter" is NOT a problem to read this article (done by an recording engineer):

http://www.digido.com/jitteressay.html

:angel:

Gabevee

Thanks.

I guess my 20 years in computing is nothing compared to a recording engineer. I didn't know that d/a converters read directly from the disc. I thought there was a memory buffer in the circuit that would totally eliminate jitter before being transferred to the D/A.

Please let us not confuse jitter with noise. Jitter is a phenomenon of timing in connection with data transfer. Again, with LSI and all running on one clock and memory buffering... there is no real problem.

It is more hype to get people to buy $8000 to $20000 "Jitter" testing equipment. I used to use a 100mHz scope to detect and adjust for jitter 20 years ago, when it really WAS a problem. Please don't tell me that technology has started going backwards.

This reminds me of those who while being well meaning claim that there is time delay smearing of the signal due to NFB, hence why it is "bad". They imagine that the signal feeds back with delay, then the same portion of signal gets fed back along with the original signal, and so on and so on and so on, sort of like multipath in FM. Ah, the attention paid to such minutia. Makes life interesting, to say the least. Now I am being sarcastic.

Try reading this:

http://www.earlevel.com/Digital%20Audio/

and this:

http://www.mscience.com/

Of particular interest is the glossary.

Gabe:yikes:

johan.vikstrom

quote:

Originally posted by Gabevee
Thanks.

I guess my 20 years in computing is nothing compared to a recording engineer. I didn't know that d/a converters read directly from the disc. I thought there was a memory buffer in the circuit that would [B]totally eliminate jitter before being transferred to the D/A.

I think I agree.

Is it not like this...

It does not even matter if it is no memory buffer before the DAC. Because both a 'serial' (one bit) and a paralell DAC will receive all bits before they latch them. So any jitter before the DAC will never affect the DAC conversion.

(jitter that is to big, if bits are missing, will affect the dac)

patwen

"Re #1. It is the ever constant sing-song of the PS and ground bounce transients. In a smoothly operating CD player, the data being read from the disc is good, no error correction, no back and forth tracking servo slewing, no sudden and irregular PS demands based on these circuits demands. The PS transients are still there, just not as many, and in a more regular fashion.

In a CD player that is reproducing a disc that needs error correction, servo tracking corrections, etc., the ever present PS sing-song is now much busier, more going on, more PS and ground bounce transients.

The FIFO buffer will be subject to the same PS issues, so will the DAC, so will the Crystal oscillator.

EVEN IF THE PS AND GROUND FEEDING THESE VARIOUS SUB-SYSTEMS WAS PERFECT, AND HAD _NO_ DEVIATION FROM NOMINAL VOILTAGE AND GROUND POTENTIAL, THE DAC (usually an LSI), THE FIFO BUFFER, THE CRYSTAL CIRCUIT WOULD ALL SUFFER FROM LIM (Logic Induced Modulation). See:

"Time Distortions Within Digital Audio Equipment Due to
Integrated Circuit Logic Induced Modulation Products"
AES Preprint Number: 3105 Convention: 91 1991-10
Authors: Edmund Meitner & Robert Gendron

Jitter introduced by using high speed mastering will find it's way into the CD player output via the read laser signal, and it's non-steady signal compared to a more steady one.

See:
http://www.eqmag.com/0003/columns5.shtml
AND
http://www.rogernichols.com/EQ/EQ_2000_02.html

http://www.AudioAsylum.com/audio/ge...ssages/977.html

Sony, and many of the major record labels have had to re-master CD's by major artists after they heard the test pressings, and found the sound to be quite rough and harsh.

As for WHY CD-R's may have less jitter than a commercial pressing, and sound better because of it, the CD-R is pre-grooved, and when burned at a 1X speed, can provide a very stable and clean series of consistent pits to be read. SOme of the really cheap IDE based CD-R burners may not improve things at all, due to poor burn timing stability or susceoptibility to outside influences. Well engineering SCSI based CD-R burners using quality media can actually improve amny commercial pressings. The exceptions are those thatused a poor time base to encode the analog data at the ADC point, that is, a certain minimum level of jitter was recorded permanently.

RE #2

Further, re the use of buffering, to this day many CD players use the embedded word clock to clock out the DAC data, rather than a crystal based master oscillator, the buffering is corrupted by the signal timing out the DAC itself.

DVD players, and SACD seem to be using some sort of packet based data transfer, and make use of a crystal based buffer, feeding the DAC with a much steadier signal. More attention seems to have been payed to the units PS, and this results in reduced jitter.

I discuss the PS issues at this page, which contains a wide ranging set of URL's that link to further info.
http://www.geocities.com/jonrisch/jitter.htm

Jon Risch"

patwen

"First, I believe he states that Jitter is introduced in the conversion process, but is eliminated in the digital storage (hard disk, etc.). But then he speaks of jittery CDs. How is a CD different from other storage media? Why is jitter recorded on a CD?"

Hello, Paul... Thanks. your comments are cogent. Apologies for the "work in progress". If we knew all the answers, we'd be geniuses! I will say that a large group of mastering engineers and critical listeners agree that CDs cut in different ways tend to sound different. The CD differs from other storage media in many ways, but the critical point is that the timing of the output clock and the speed of the spinning disc are related. The output of the CD player is a clocked interface, and the data are clocked off the CD disc in a "linear" fashion, one block of data after another. A buffer is used, which theoretically cleans up the timing to make it regular again. And for the most part, it does.

A lot of this is theory... no one has proved it as fact. And there may be more than one mechanism causing jitter taking place.

To obtain jitter in the low picosecond region requires extremely accurate timing. Any leakage current (interference) between the servo mechanism controlling the speed of the spinning disc and the crystal oscillator controlling the output of the buffer may unstabilize the crystal oscillator enough to add jitter to the clock signal. This does not change the data, by the way. If the servo is working harder to deal with a disc that has irregularly spaced pits or pits that are not clean, perhaps leakage from the servo power affects the crystal oscillator. It doesn't take much interference to alter a clock by a tiny amount.

This jitter is "ephemeral", though, because you can copy this data (irrelevant to the clock), and then play it back again from a more steady medium... and make it sound "good" again. This is not a permanent problem.

What makes the CD different from a hard disc, is the HD uses an asynchronous interface (SCSI or IDE). The disc is always spinning at the same high speed and the heads land on the spot you need when the data is requested. The data coming out is completely unclocked (it comes out in bursts) and has to pass through the SCSI barrier into a buffer located in a different chassis than the hard disc (the computer)... thus, there is great distance between the varying currents of the spinning disc motor and the oscillator driving the output of the buffer in the computer chassis. Since the computer chassis power supply only has to power the output oscillator, the result can be much more stable. Depends on how good the designer did his/her homework. Same for a CD Player... there are audiophile CD players where great attention has been made to power supply design, and these players exhibit much less jitter and better sound.

It is also possible to build a CD player based on a SCSI mechanism... possibly such a player would be more stable in playback than a standard CD player. You would have a computer in its own "cleaner" environment buffering the data. The Alesis Masterlink is such a player, and in another "chapter" of my work in progress I will have something to say about its audible performance.

I'd like to tackle a 200 page booklet to put all the pieces together someday, but haven't the time. I think in our FAQ there are some explanatory letters which help to cover the rough spots.

Gabevee

Gosh, all this knowledge is now giving ME the jitters. :devily:

I didn't know that a single bit of data (either a one or a zero) can contain so much more, or that a 10-20 picosecond spike or time difference (translating into terahertz frequency) was such a problem for the 96 kHz sampling of a recording studio, even with 8X oversampling (that would barely reach 1 megahertz, BTW).

If they have so much trouble with their recording equipment, then they need to dismantle their 20 year old technology and get new stuff (notice how the author of one of your articles exagerates the 72,000,000,000 copies of the CD. I doubt that Steely Dan's new CD broke 1 million, let alone 72 billion, as much as I love their music. I know, he was probably being facetious).

There are many things being ignored in these "articles" and/or the term "jitter" has a new meaning now that I am unaware of.

As Johan touched on and I didn't even think about, the data has to undergo serial to parallel conversion as well. This means more buffering and memory (very key to the process of s-p conversion) and program error correction, if any (errors). Oh, the buffering part takes weak and dirty (jittery?) data and cleans it up, BTW. Or am I also out of touch with these facts as well?

And as he said, once the latch is set to a state in memory, there aren't other bits of data residing in that one bit of memory cell.

If memory serves, even if the circuitry is on separate boards, and each circuit has its own clock, there is such a thing as synchronization that occurs (AKA handshaking... in the datacomm world), that must occur. Otherwise, nothing would work. In fact there is more to worry about right here under my fingertips than in any CD (or analog to digital) anything when it comes to clean and error free data transfer, from my fingers to your eyes.

Now if we say noise is a problem, which is what you sound like you are referring to (as well as those articles), then I say... the power supply and support circuitry suck to begin with. Get better equipment. OR put some filter caps in strategical locations to filter out the noise. Otherwise we aren't comparing oranges to oranges.

As for the CD and DVD players at home and in my car... they use brute force power supplies with voltage regulators. No leakage (jitter?) from 80kHz switching there.

While I am sure they mean well, I think newer recording engineers, like electronics technicians, get superficial knowledge of theory. Especially these days where, having talked to several college professors about their curriculum, they have to trim down