And then flip them back and forth at least two and preferably three or more times, not only to verify that your perceptions are consistent, but that the perceived difference (if any) is not the result of an extraneous variable (for example, changes in contact integrity, changes in AC line voltage or noise conditions, changes in room temperature or humidity, etc).
Hi Al,
As for contact integrity I would suggest cleaning the contacts before swapping the cables end for end and then listening for a while to get used to any differences in sound from the system. This should establish a common base line for the test. Then flip the cables end for end. Listen to the same music that listened to before flipping the cables.
Room environment should not change in just a couple of hours or so, of the same day, for the listening test.
Jim