If that's the only information recorded on a CD I have the following questions:
1/ There were discussion here before regarding a copied CD and its original CD may have different sound quality due to timing(better or worst constant clock speed), correct?
2/ How can we explain the different output level(power) between the original and copied CDs? They both have the same number of ones and zeros, may be the timing might affect the brightness or smoothness of the recorded music, but what affect the output level?
Thanks in advance,
Chris
1/ There were discussion here before regarding a copied CD and its original CD may have different sound quality due to timing(better or worst constant clock speed), correct?
2/ How can we explain the different output level(power) between the original and copied CDs? They both have the same number of ones and zeros, may be the timing might affect the brightness or smoothness of the recorded music, but what affect the output level?
Thanks in advance,
Chris
Well as said before, different writers and media seem to sound different due
to writing quality. An idea give these articles:
http://www.cdrinfo.com/Sections/Articles/Specific.asp?ArticleHeadline=Jitter+Tests&index=0
http://www.cdrinfo.com/Sections/Articles/Specific.asp?ArticleHeadline=Writing+Quality&index=0
But a difference in the output level is a bit strange and more likely to
be introduced with a wrong setting in your copy programm, like "normalizing"
Or the copy is that bad, that it introduces that much noise it even seems louder,
i can´t imagine that.
to writing quality. An idea give these articles:
http://www.cdrinfo.com/Sections/Articles/Specific.asp?ArticleHeadline=Jitter+Tests&index=0
http://www.cdrinfo.com/Sections/Articles/Specific.asp?ArticleHeadline=Writing+Quality&index=0
But a difference in the output level is a bit strange and more likely to
be introduced with a wrong setting in your copy programm, like "normalizing"
Or the copy is that bad, that it introduces that much noise it even seems louder,
i can´t imagine that.
Copied CD
Hi chris,
I discovered the copied CD has a very noisy eyepattern.
Eyepattern is the signal coming off from the read electronics. It is a bunch of sinusses not a series of ones and zero's (squarewaves?).
The copy sounded slightly more digital than the original but did not skip or mistrack.
Hi chris,
I discovered the copied CD has a very noisy eyepattern.
Eyepattern is the signal coming off from the read electronics. It is a bunch of sinusses not a series of ones and zero's (squarewaves?).
The copy sounded slightly more digital than the original but did not skip or mistrack.
one & 0s
Wombat, thanks for those links, interesting read. From the first one I gather that there seems some limit on the minimum jitter that can be reached of around 20nS, whatever brand recorder or medium is used. This is good news for me, since I am about to purchase a digital piece of hardware with jitter guaranteed below 10nS, so that doesn't seem a problem.
In my above post I reacted to the level differences (or absence thereof), which isn't addressed by the links provided. Have you any documented research on this ?
Jan Didden
Wombat, thanks for those links, interesting read. From the first one I gather that there seems some limit on the minimum jitter that can be reached of around 20nS, whatever brand recorder or medium is used. This is good news for me, since I am about to purchase a digital piece of hardware with jitter guaranteed below 10nS, so that doesn't seem a problem.
In my above post I reacted to the level differences (or absence thereof), which isn't addressed by the links provided. Have you any documented research on this ?
Jan Didden
Sorry janneman.
I have not found anyone claiming the copy sounds different in level.
Thats why i think it must be wrong setting in the copy program.
Some said it sounds horrible bright in opposite to the original, maybe this creates
a subjective feeling of changing the level!?
I can´t confirm that.
I have not found anyone claiming the copy sounds different in level.
Thats why i think it must be wrong setting in the copy program.
Some said it sounds horrible bright in opposite to the original, maybe this creates
a subjective feeling of changing the level!?
I can´t confirm that.
It is interesting to note:
A CD is encoded with a series of nine different pit lengths. Not ones and zeros. The output of the "light to electricty converter" looks like nine sine waves of different time periods.
If you look at a CD block diagram, there is a box typically identified as a demodulator. This is what converts these sine waves into ones and zeros.
Also it might be important to note that the entire surface of a CD is reflective. How the laser gets turned on and off is the fact that the pit's depth (as I recall, 1/4 wave length deep) is such to cause phase cancellation on reflection.
Once I learned these 2 facts, I began to believe CD transports can sound different. The idea of "it is digital, either it works or it doesn't" might not always be true.
Aud_Mot
A CD is encoded with a series of nine different pit lengths. Not ones and zeros. The output of the "light to electricty converter" looks like nine sine waves of different time periods.
If you look at a CD block diagram, there is a box typically identified as a demodulator. This is what converts these sine waves into ones and zeros.
Also it might be important to note that the entire surface of a CD is reflective. How the laser gets turned on and off is the fact that the pit's depth (as I recall, 1/4 wave length deep) is such to cause phase cancellation on reflection.
Once I learned these 2 facts, I began to believe CD transports can sound different. The idea of "it is digital, either it works or it doesn't" might not always be true.
Aud_Mot
pinkmouse said:
Don't know, but some people report that CDR copies sound
better than the originals, which would then mean that there
are reading error problems also with pressed CDs. If CDRs
can sometimes sound better, I would guess it is because
they are thicker and mechanically more stable and/or because
they usually have a better reflection layer than pressed CDRs
(silver or gold rather than aluminum and also thicker).
Apart from the jitter issue, bits is in fact bits.
There are many many read errors when playing back a CD. You'll probably never get exactly the same stream of "1"s and "0"s from the demodulator, even if you play the same CD on the same player. This is due to scratches, dust, vibration, fingerprints...
But, because of a high number of nested parity bits (cross interleave Reed Solomon code) most read errors and their position in the data stream can be recognized. That's the good thing about digital: If you get a data bit of "0" and the information that there was a read error at this very bit, you can safely assume the error will be corrected if you set that bit to "1". If there are too many errors (which doesn't occur that often, but in most cases happens before the CD starts skipping) and correction is impossible, samples might be interpolated or the last valid sample will be held until a new valid sample arrives. Only this kind of "read error" is audible.
So the statement from the Sony technician seems to be wrong, because error correction as such is inaudible. Only if error correction fails and other techniques (such as interpolation between valid samples) are applied, the "1"s and "0"s fed to the D/A chip are different from what was pressed on the CD.
There was a simple counter circuit published in Elektor, which could be connected to a dedicated "uncorrectable error" pin of a Philips SAAxxxx chip (don't remember exactly) to count the actual number of uncorrectable errors on a CD during playback.
This way we could find out if there are really big differences in the quality of CD-Rs or if we can blame the difference in sound quality solely to the jitter issue.
There are many many read errors when playing back a CD. You'll probably never get exactly the same stream of "1"s and "0"s from the demodulator, even if you play the same CD on the same player. This is due to scratches, dust, vibration, fingerprints...
But, because of a high number of nested parity bits (cross interleave Reed Solomon code) most read errors and their position in the data stream can be recognized. That's the good thing about digital: If you get a data bit of "0" and the information that there was a read error at this very bit, you can safely assume the error will be corrected if you set that bit to "1". If there are too many errors (which doesn't occur that often, but in most cases happens before the CD starts skipping) and correction is impossible, samples might be interpolated or the last valid sample will be held until a new valid sample arrives. Only this kind of "read error" is audible.
So the statement from the Sony technician seems to be wrong, because error correction as such is inaudible. Only if error correction fails and other techniques (such as interpolation between valid samples) are applied, the "1"s and "0"s fed to the D/A chip are different from what was pressed on the CD.
There was a simple counter circuit published in Elektor, which could be connected to a dedicated "uncorrectable error" pin of a Philips SAAxxxx chip (don't remember exactly) to count the actual number of uncorrectable errors on a CD during playback.
This way we could find out if there are really big differences in the quality of CD-Rs or if we can blame the difference in sound quality solely to the jitter issue.
The first requirement for a Bit perfect copy is the best "reader" program.
Take a look at; http://www.exactaudiocopy.de/
With this program it is possible to make Bit identical copies and jitter has really nothing to do with this matter.
But it canvery well be that an ordinary CD player at some point gives up on error correction and makes a qualified guess - once you have used the above program you will have an idea on how many times that would happen and maybee be suprised !
The original problem of the this thread points at a Normalisation function either in the ripper or the Burner part of the copy chain - This must of course be avoided.
I would like to hear anybody with solid resulst based on blind test that can give differences between original and copied CD ( using the above program )
Br
Morten
Take a look at; http://www.exactaudiocopy.de/
With this program it is possible to make Bit identical copies and jitter has really nothing to do with this matter.
But it canvery well be that an ordinary CD player at some point gives up on error correction and makes a qualified guess - once you have used the above program you will have an idea on how many times that would happen and maybee be suprised !
The original problem of the this thread points at a Normalisation function either in the ripper or the Burner part of the copy chain - This must of course be avoided.
I would like to hear anybody with solid resulst based on blind test that can give differences between original and copied CD ( using the above program )
Br
Morten
1s & 0s
It is apparently a stubborn mistake to think that error correction does lead to errors. It does not. Error correction does exactly what it says - it corrects the error. Therefore, after error correction has taken place, the resulting bit stream is identical to the original.
Jan Didden
pinkmouse said:
It is apparently a stubborn mistake to think that error correction does lead to errors. It does not. Error correction does exactly what it says - it corrects the error. Therefore, after error correction has taken place, the resulting bit stream is identical to the original.
Jan Didden
Re: 1s & 0s
Jan, it's true what you are saying but the error correction is only good for "not too many errors". If you have too many errors you can hear it. I have noticed that my old CD likes slow speed burned CDR better than x8, x12. It can have something to do with "sharper" pits.janneman said:
Better copies
OK, maybe I am crazy, and this was not a blind test, because I did it by myself, but I think my copies sound better than the originals.
I have been messing with this for a little while, but got serious after reading this,
http://www.genesisloudspeakers.com/newshmfeb03set.html
I happened to have some black CDR's it talked about, so I decided to give it a try.
I bought an iomega predetor external drive, as referenced (from Ebay, for about $60 reconditioned). I put a board down on the carpet in front on my computer, put the board on some vibrapods I had, put the drive on some Diyumas I made a while back, put some lead weight on the shelf, a little lead on the drive. I also treated the CDR with Auric Illuminitor.
I have an backup hard drive I used to write the music to, defragmented the drive, then read in the originals. Restarted the PC, then wrote at 2X using EasyCD.
All the copies I have tried so far sounded better. Listened to Sarah Brightman "La Luna" the other night, think the soundstage was a little bigger, her voice sounded clearer, and just overall the copy was more musical.
I plan to make more copies in the future, and since I had everything on hand to try this but the drive, it was well worth the money and effort. I also need to experiment some more, to decide what setup will give me the best sound, then I plan to redo all the CD's I listen to.
Randy
OK, maybe I am crazy, and this was not a blind test, because I did it by myself, but I think my copies sound better than the originals.
I have been messing with this for a little while, but got serious after reading this,
http://www.genesisloudspeakers.com/newshmfeb03set.html
I happened to have some black CDR's it talked about, so I decided to give it a try.
I bought an iomega predetor external drive, as referenced (from Ebay, for about $60 reconditioned). I put a board down on the carpet in front on my computer, put the board on some vibrapods I had, put the drive on some Diyumas I made a while back, put some lead weight on the shelf, a little lead on the drive. I also treated the CDR with Auric Illuminitor.
I have an backup hard drive I used to write the music to, defragmented the drive, then read in the originals. Restarted the PC, then wrote at 2X using EasyCD.
All the copies I have tried so far sounded better. Listened to Sarah Brightman "La Luna" the other night, think the soundstage was a little bigger, her voice sounded clearer, and just overall the copy was more musical.
I plan to make more copies in the future, and since I had everything on hand to try this but the drive, it was well worth the money and effort. I also need to experiment some more, to decide what setup will give me the best sound, then I plan to redo all the CD's I listen to.
Randy
Re: Better copies
A nice read what others think about this topic is here.
http://www.hydrogenaudio.org/index.php?act=ST&f=1&t=6907&hl=insanity&
randytsuch said:
A nice read what others think about this topic is here.
http://www.hydrogenaudio.org/index.php?act=ST&f=1&t=6907&hl=insanity&
I agree that copies sound different then originals, sometime better but mostly worse.....
As someone hinted our CD players are not ideal and almost everything that goes on affects all parts of the machine.
A bit is a bit and when they are not where they are supposed to be you will most likely hear it as glitch or a blop.
My view on this is that depending on how "easy" or "difficult" the disc is to read it will draw a different current patterns and ultimatly influence the jitter structure in the output signal...and we percieve it slightly different.
I've done a lot of building and testing with separeta dacs and when one uses some type of completly separate reclocking I find it impossible to notice any difference between the original and copy.
I've also found thet the the reclocking curcuit has a VERY direct influance on percieved sound quality......
As someone hinted our CD players are not ideal and almost everything that goes on affects all parts of the machine.
A bit is a bit and when they are not where they are supposed to be you will most likely hear it as glitch or a blop.
My view on this is that depending on how "easy" or "difficult" the disc is to read it will draw a different current patterns and ultimatly influence the jitter structure in the output signal...and we percieve it slightly different.
I've done a lot of building and testing with separeta dacs and when one uses some type of completly separate reclocking I find it impossible to notice any difference between the original and copy.
I've also found thet the the reclocking curcuit has a VERY direct influance on percieved sound quality......
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