It is indeed good to know that JRiver outputs the same on a mac and a pc but, just to be a bit pedantic, the computeraudiophile tests don't show that JRiver is bit-perfect on either player, just that the outputs were identical. They could be identically wrong! For completeness it would have been good if the captured outputs had been compared to the file that was ripped. Some DACs have tests of bit-perfectness - you play a special test file into them and they tell you if they recognise it and it is bit-perfect; some time ago I borrowed an Audiolab M-DAC which has such a test and, as you would expect and hope, JRiver passed fine. Given the propensity operating systems have for doing things to audio data that you don't want done, I wonder if there is some simple way of capturing the data that comes out of a USB port and comparing it to the source? Or is the blue light in JRiver and absolute absolute guarantee?