I am a fan of Agatha Christie's Hercule Poirot mysteries as portrayed in the BBC series starring David Suchet. In fact, he's one of my all time favorite actors portraying a character. It's a delicious series. And the more you watch the greater your awareness of Christie's formulaic approach to laying out sparse clues and misdirecting you from the real killer. And even knowing this I am always surprised at the outcome.
Let's approach solving our current mystery, why copies often sound better than originals, in the same manner as Hercule Poirot would; by using 'our little grey cells'.
So, what are some of the facts we know? Perhaps the most important is 'bits are bits'. This means the bits are the same between the original and the copy. We also know that copies made from identical media and methods sound the same. Take two off-the-shelf CDs from an artist and if they were from the same CD stamper they sound the same (yet they are copies of the master, just not copies of themselves). Make a CDR copy of that same commercial pressing and it sounds different. So, we know different media and different process sound different. Perhaps these are enough clues to begin with.
It has been speculated that the process of ripping a CD onto a CDR (recordable CD) or hard drive accounts for some differences in sound. Yet, the bits between the two differ not. Therefore, we can eliminate that speculation as a likely suspect. It has also been suggested that perhaps the ripping process changes the jitter recorded onto the CDR or hard drive vs. that which is on the CD. Yet, we know there is no clock or timing reference on either the CD or the CDR. This is an important clue in our search. Hard drives, SD cards, CDs, CDRs haven't any timing information embedded in them. Instead, the bits are recorded one after another without regard to timing. So jitter is a less likely candidate as a suspect, although jitter's alibi is a bit shaky still, since we know Jitter's always cropping up somewhere in the chain.
The mystery deepens knowing the culprit cannot be the veracity of the bits or their timing, at least not their timing as embedded on the disc itself.
Clue. One of Christie's style is to drop small factoids here and there that alone mean nothing, but when placed in context mean everything.