Does the quality of a digital signal matter?

Shadorne - CD copy should be bit perfect only if CD is copied as data and not as a music CD. For example - with I tunes I can make copy of CD that is not readable as data using MAX (with "do not allow to skip" option). You can make 10 copies of scratched CD with Itunes or similar program and every copy will be different (because many sectors might be on the edge of readability).

I use MAX for ripping but have few CDs that required use of Itunes to rip them because MAX with multiple attempts was failing.

The worse part is that Cross Interleaved Reed Solomon error correction code is approximating/interpolating uncorrectable data. Read what I found i Wikipedia under "ripping"

"CD audio has two major design constraints that make it difficult to obtain accurate copies in the form of a standard digital file. First, the system is designed to provide audio in real time in order to ensure continuous playback without gaps. For this reason, it does not provide a reliable stream of data from the disc to the computer.

Secondly, the designers felt that it would be preferable for major scratches in the disc to be covered up rather than resulting in total failure. Normally, an error correction system such as Reed Solomon would provide either a perfect copy of the original error-free data, or no result at all. However, CD audio's Cross-interleaved Reed-Solomon coding includes an extra facility that interpolates across uncorrectable errors. This means that the data read from an audio CD may not in fact be a faithful reproduction of the original.

Another practical factor in obtaining faithful copies of the music data is that different CD drives have widely varying quality for reading audio. Some drives are thought to deliver extremely accurate copies while others may do little or no error correction and even misreport error correction information."

Since the CD copy should normally be a bit perfect copy (you can confirm this easily using a computer), you may want to invest in a better CD player or DAC. What you are experiencing are differences in sound quality due to small differences in the media disc such as weight, color, coating, central hole alignment, balance of the disc etc. - normally a good player will be immune to such differences - it should read the bits correctly without affecting the built in DAC and low jitter clock:it should result in identical sound.
Shadorne

I knew when I posted it,... I would get that answer.... All I can say to you is, have you tried it? I suggest you try it for yourself.

I have a couple of dealers in my area that said the same thing as you. In both cases I proved them wrong on their own systems. In fact the more revealing the system the easier it is to hear the difference.

My experience the "Exact copy" from a home PC lacks the body and fullness as a copy made on a decent stand alone CDR recorder..... A couple of key things to listen for is Female vocals, and piano.

The manufacture of the blank CDR will also make a difference.

If redbook manufacture is supposed to commence play at exactly 2.00 seconds from the true zero pressed on the cd aren't we discussing data here.Programs like the forgotten Perfect Rip take this very seriously,correcting for sub-channel data in the process etc.Bit correction for offsets is what it is all about.I have discovered that Nero CD Speed Tool does report offsets correctly,just giving a total figure.Perfect Rip confirms Nero and this means that the Accurate Rip database is incorrect.All offsets given there are +30 samples out for every drive listed.I no longer get silly anamolies with ripping,they are perfect every time.I might add that voltage brown-outs and spikes badly effect ripping also.You reap what you sow.

Kijanki,
The Reed Solomon interleave is actually quite robust however CD players will indeed "interpolate" as a last resort when data is missing

It is true that you might not know when your CD player is interpolating unless the disc is quite badly damaged and you get pops or clicks. Normally you should be well aware of errors when music is copied with a PC with good software (sometimes you need to set the software to warn you about read errors).

I have had some CD's that suffered CD rot - they played on a CD player but could not be copied without error on a PC - to me this means that they are beyond repair and the data cannot be recovered - but this problem is possible with any digital format that gets really badly corrupted or damaged. Under normal use with good quality discs one should not normally run into problems.

I knew when I posted it,... I would get that answer.... All I can say to you is, have you tried it? I suggest you try it for yourself.

The science is pretty clear on this. If you suffer issues then the difference between the disc material is causing poor D to A conversion. (The machine gets the digital info off the disc but is unable to convert it reliably without audible distortion)

I am not surprised that there were differences - there is a lot of inadequate equipment out there - much of it at the high end. Jitter only became well understood in the mid 90's and it only takes poor isolation of the servo motor driving the CD lens from the clock driving the DAC to get distortion due to jitter. Since the lens servo and motor will be acting in a cyclical pattern (highly likely since it is reading a rotating disc) then these patterns can mess up the sound quality of the CD player - if you replace the disc and it behaves a little differently when rotating then bingo you get a slightly better or worse sound.

The solution is to get a better CD player that will read the data without affecting the quality of D to A.