Interesting observations.
Sidssp - Did you try ripping the tracks that sounded different on the burned CDs and comparing them to each other and to the original ripped tracks? It would be interesting to see if the bits are different. If so, then the burning process may be the issue - which I think is what I think you concluded.
Peter_S What do you think caused the differences you hear? Do you agree if the bits are the same, the files should sound the same? If so, you might want to compare the actual files bit by bit. It is certainly possible that there is some error in the conversion process. You could compare the Apple lossless files with a file compare utility like fc/b, although it is pretty crude. You can also convert the Apple lossless to wav and compare those files using EAC or foobar. As I said above, when I ripped tracks to Apple lossless with iTunes and converted them to wav and compared to EAC ripped tracks, they were identical. Have not tried a bit compare after doing a wav to Apple lossless conversion but could try it. Also you could convert the Apple lossless lossless file that was converted from the EAC wav file back to wav and compare it to the original EAC wav file to see if the round trip introduced differences. EAC has a good comparison routine, although you have to set the disk offsets to 0 when ripping with EAC to do the comparison. Another interesting thing to do is to take the EAC wav and a iTunes ripped Apple lossless file converted to wav and use the ABX facility in foobar to do a blind test of the two files. Much harder to do comparisons with iTunes. (I don't want to get into a discussion of blinding testing - just wanted to point out the utility in foobar.)
Sidssp - Did you try ripping the tracks that sounded different on the burned CDs and comparing them to each other and to the original ripped tracks? It would be interesting to see if the bits are different. If so, then the burning process may be the issue - which I think is what I think you concluded.
Peter_S What do you think caused the differences you hear? Do you agree if the bits are the same, the files should sound the same? If so, you might want to compare the actual files bit by bit. It is certainly possible that there is some error in the conversion process. You could compare the Apple lossless files with a file compare utility like fc/b, although it is pretty crude. You can also convert the Apple lossless to wav and compare those files using EAC or foobar. As I said above, when I ripped tracks to Apple lossless with iTunes and converted them to wav and compared to EAC ripped tracks, they were identical. Have not tried a bit compare after doing a wav to Apple lossless conversion but could try it. Also you could convert the Apple lossless lossless file that was converted from the EAC wav file back to wav and compare it to the original EAC wav file to see if the round trip introduced differences. EAC has a good comparison routine, although you have to set the disk offsets to 0 when ripping with EAC to do the comparison. Another interesting thing to do is to take the EAC wav and a iTunes ripped Apple lossless file converted to wav and use the ABX facility in foobar to do a blind test of the two files. Much harder to do comparisons with iTunes. (I don't want to get into a discussion of blinding testing - just wanted to point out the utility in foobar.)