Why does the copy sound better than the original

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?

eoff:
I'm not interested in doing the experiment. You are. Therefore, my suggestion was that YOU do it, not direct me to do it. I'm simply REPORTING what Peter McGrath and Robert Harley posited. It was THEY who posited that the larger pits allowed more information to be recovered more cleanly, much in the way that Classic Records put entire symphonies on 45 rpms, instead of 33, because, they said, they grooves in a 45 were larger and thefore, it improved the sonics.
People offer theories all the time. It's how life advances.
I see no need in trying to prove or disprove someone else's speculation, if they are the experts. That's why I made it clear that this point of view came from others, specifically named them, and where the information could be found (TAS). If you write TAS, or Peter McGrath, I'm sure they'll be happy to open a dialogue about it.

I am not a professional reviewer or listener but I'm not deaf either. I have listened to many copies of cds and they don't sound better to me. Someone else may hear an improvement but there are many possible explanations why.

If you make a copy of a cd and then make a copy of the copy and on and on I think that there will eventually be an obvious degradation of the sound, so I don't know why the first copy would be an improvement.

Dougmc, off the top of my head, Red Book CD specifies 16 bit words and 44.1 kHz sample rate. Not sure I can answer where the 20 and 24 bit words enter the picture for CD. If we compare Red Book to Blu Ray for audio, Blu Ray will provide higher resolution than Red Book CD since resolution is determined by bits per word. But I also think that a debate over CD vs Blu Ray or even CD vs CD-R is moot for purposes of the "does the copy sound better than the original?" argument since a CD-R and its CD-R copy can be compared sonically, thus eliminating variables related to physical differences that might exist between CD and CD-R such as pit size, metal layer, etc. or how the laser reads the pits

Gbmcleod wrote,

"I'm simply REPORTING what Peter McGrath and Robert Harley posited. It was THEY who posited that the larger pits allowed more information to be recovered more cleanly, much in the way that Classic Records put entire symphonies on 45 rpms, instead of 33, because, they said, they grooves in a 45 were larger and thefore, it improved the sonics."

If that is what they reported it doesn't make too much sense. The 45 sounds better than a 33 because of greater excursion of the stylus in the groove (dynamic range) and higher rotation speed of the disc. In the case of the CD, the photodetector is simply detecting an ON and OFF conditions that are a function of the pits. The CD laser spot diameter needs to be larger than the width of the pits because the laser reflection off the metal layer cancels the laser reflection off the pit, producing the OFF condition as seen by the photodetector. The ON condition is simply the pure laser spot reflection from the metal layer (land) between the pits. Of course, all of the geometry, the length and width of pits and lands, the diameter of the laser spot, the depth of the pits, etc. has been worked out in advance.