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Old 9th March 2003, 01:10 AM   #11
OliverD is offline OliverD  Germany
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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.
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Old 9th March 2003, 03:58 AM   #12
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Default Servo Dependencies.

Take a look at the focus error and tracking error signals when playing different cds.
Those signals tell you a lot.

Eric.
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Old 10th March 2003, 06:45 AM   #13
Henckel is offline Henckel  Denmark
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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
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Old 10th March 2003, 07:01 AM   #14
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Default 1s & 0s

Quote:
Originally posted by pinkmouse
I was once told by a Sony tech involved in broadcast that the reason a disc my sound different when copied is due to imperfections in the CDR disc leading to increased error correction in the player.

At the time it seemed a reasonable argument, does it have any basis in fact?

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.

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Old 10th March 2003, 08:17 AM   #15
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Default Re: 1s & 0s

Quote:
Originally posted by janneman
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, 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.
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Old 11th March 2003, 01:06 AM   #16
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Default 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
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Old 11th March 2003, 10:26 AM   #17
Wombat is offline Wombat  Germany
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Default Re: Better copies

Quote:
Originally posted by randytsuch
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

A nice read what others think about this topic is here.
http://www.hydrogenaudio.org/index.p...7&hl=insanity&
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Old 11th March 2003, 01:39 PM   #18
SY is offline SY  United States
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It's an easy thing to do, why not try that test blind? Just have your accomplice remove and replace the discs each switch, regardless of whether they're being changed or not. It might prove... ah... illuminating.
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Old 11th March 2003, 05:16 PM   #19
A 8 is offline A 8  Sweden
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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......
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Old 11th March 2003, 06:49 PM   #20
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Default Reclocking

Quote:
Originally posted by A 8


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......
Hi A 8,
What type of separate reclocking did you use? What frequency and clock?

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