[prescient]

I was just curious if anyone has ever used a program such as Audio DiffMaker to check for differences between the output of various DACs.  Something like EMU 0404 USB vs Bechmark Dac1?  For those who have no idea what Audio DiffMaker is just click the link.  In short it basically makes two audio recordings and subtracts one from the other.  If the subtraction is perfect then there is no difference in the audio signal and if it is not then you can listen to what is different from the first recording to the second.
 
http://libinst.com/Audio%20DiffMaker.htm