Why does the copy sound better than the original

Geoffkait wrote:

That's weird. The pits are narrower on Blu Ray discs and Blu Rays sound better than either CD or CD-R. Wassup with that?

Comparing CD to Blue Ray may be an apples to oranges comparison. Although I can't list any, Blue Rays may sound better for other reasons than pit size. Also consider that the reason the Blue Ray pit size is smaller than CD pit size is that the Blue Ray laser wavelength is also smaller than its CD counterpart. Maybe a CD copy sounds better than the original because the CD laser wavelength remains the same size while the pit size increases (less chance of light wave diffraction?).

Dougmc wrote,

"Comparing CD to Blue Ray may be an apples to oranges comparison. Although I can't list any, Blue Rays may sound better for other reasons than pit size."

The primary reason is bit size, since that determines density of data as well as resolution (for both audio and video). That is why the video quality of Blu Ray is so much better than DVD. That's the whole point of the Blu Ray technology.

"Also consider that the reason the Blue Ray pit size is smaller than CD pit size is that the Blue Ray laser wavelength is also smaller than its CD counterpart. Maybe a CD copy sounds better than the original because the CD laser wavelength remains the same size while the pit size increases (less chance of light wave diffraction?)."

As I already mentioned, copy a CD-R from a CD-R and you'll have your answer.

It sounds as though you know how to do this, Geoff. I do not. How about doing it as you have the knowledge and filling us in on what you heard?

Gbmcleod, as I said, take a commercial CD, make a CD-R copy. Then listen to the CD-R copy to see if it sounds better, the same as, or even perhaps worse than the original commercial CD. If the CD-R copy does sound better than the original, we don't know why, it could be anything.

But to eliminate the possibility that the reason is due to some advantage CD-Rs might have over a standard CD, whether it's differences in the pits or the clear layer or the metal layer, whatever, make a copy of the CD-R using the same brand of CD-R. Listen to the copy of the CD-R. If that sounds better than the first CD-R then there must be something else going on besides differences in pits (or anything else) between the commercial CD and the CD-R. Wouldn't you agree?

Geoffkait

I don’t have any opinion about whether or why a CD copy sounds better than the original. My earlier post was directed solely to your comment that larger pits on a CD copy couldn’t be a reason they sound better than an original CD, because Blue Ray discs, which sound better than CDs, have pits that are smaller than the pits on CDs. On that position, I have a comment and a question.

Comment

In your response to me, you elaborated that a smaller pit size allows more pits (and bits) to be placed on a Blue Ray disc, providing more information, greater detail and better sound. I agree with your observation that a Blue Ray disc can hold more information than a CD, but that explanation relates to how many pits there are, not the way the laser reads the smaller pits.

A CD original and a CD copy contain the same number of pits, even if the pits on the copy are larger, so the amount of information on the original and the copy is the same. The reason the Blue Ray is superior to a CD, namely more information, does not exist when comparing a CD copy to a CD original. Therefore, the smaller pit size of Blue Ray and the superiority of its sound do not together support the conclusion that a smaller CD pit size would improve CD sound or the conclusion that it would be impossible for a larger CD pit size to improve CD sound.

Question

I understand that smaller pits on a Blue Ray disc (and a smaller wavelength laser that can read the smaller pits) allows more digital information to be squeezed onto the disc, but how is the additional information translated into more detailed sound? The Blue Ray article on Wikipedia has a table of audio formats used for Blue Ray. This table shows much higher bitrates for Blue Ray formats (as much as 24.5 MBit/s) compared to CD (1,441.2 Kbit/s), which means much more digital information could be read per second. However, the table also shows the number of bits per sample for Blue Ray audio formats is either 16, 20 and 24, the same numbers as for different flavors of CD. The same table also shows sample rates of 48, 96 and 192 Khz, all of which are also available on CD. Although Blue Ray can read more information per second, it appears that it reads the same size samples at the same rate as CD, so how is the greater amount of information stored on the disc being translated into better sound? Is the superiority of Blue Ray format only a future possibility awaiting a new digital format with larger samples and/or higher sampling rates? If Blue Ray currently sounds better than CD, is it mostly the result of multi-channel versus stereo spatial presentation?