Curtis what would immediately come to my mind is that he turned the sound off or at least down instead of just pulling off the cable. When the new cable was plugged in the volume wasn't restored to precisely the same level. One of the key requirements in a double blind test is that volume levels be matched to within 0.1dB. Even a small volume increase not clearly apparent as such leads to conclusions that the higher volume is clearer and better in general.

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Enjoy the music, not the equipment.