Pedja said:
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)
johan.vikstrom said:
Take nerves also in consideration... and you're right again, it is still fun.
Pedja
Christer,
Of course I took it in the spirit it as meant. I was just trying to be a 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 crap 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
Of course I took it in the spirit it as meant. I was just trying to be a 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 crap 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
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
@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
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
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
If you want to make bit for bit copies on a PC
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
out there interested?
Ken L
PS although no longer supported by the factory - basic tech support available right here on this forum
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
out there interested?Ken L
PS although no longer supported by the factory - basic tech support available right here on this forum
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.
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.
Surprised ...
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/general/messages/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".😎
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/general/messages/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".😎
Re: Surprised ...
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.
patwen said:
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.
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.
😉
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.
😉
To: johan.vikstrom & chris ma
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 ... 🙂
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 ... 🙂
Re: To: johan.vikstrom & chris ma
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 ?
patwen said:
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 ?
Re: Surprised ...
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
patwen said:
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
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
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
save me from re-inventing the wheels ...
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
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
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 Audio/
and this:
http://www.mscience.com/
Of particular interest is the glossary.
Gabe
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 Audio/
and this:
http://www.mscience.com/
Of particular interest is the glossary.
Gabe
Gabevee said:
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)
Some more quote from John Risch
"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/general/messages/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"
"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/general/messages/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"
Q & A on the difference betwen PC data and CD data
"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.
"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.
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