Have you done a blind test, having somebody switching between the two power cords without you knowing which cord is being used and then see if you can tell the difference?
I suspect that something else is responsible for the difference you heard or thought you heard.
True double-blind testing is the definative lab test to determine the difference between any two or more options, and the results are generally very accurate IME.
Good point,thanks!
It was a noisy soundcheck on the stage,so .... it could be something else,but I should do the blind test next time.