Ones and zeros recorded on CDs

[chris ma]

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

[SY]

If a digital-to-digital copy is made (i.e., no D/A conversions, rate conversions, compression, etc.), the level will not be different. Bits really is bits.

[jan.didden]

Originally posted by chris ma
[snip]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

No need to explain because there is no difference.
Howzat for an easy answer?

Jan Didden

[Wombat]

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/Arti...+Tests&index=0

http://www.cdrinfo.com/Sections/Arti...uality&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.

[Elso Kwak]

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.

[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

[Wombat]

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.

[Aud_Mot]

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

[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?

[Christer]

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?

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).