Hot / Neutral Reversed

I dropped an extra $2 for an extra-fancy version w/ rubber grips on the sides:

https://www.amazon.com/gp/product/B000RUL2UU/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1

All the other outlets on the circuit tested fine. It just happened to be the outlet all my equipment used (save my Vandersteen Quatro CTs) that was reversed. 

If it was wired incorrectly at the outlet I would check the wiring all the way back to the main distribution panel and use a circuit tester just to make sure. This is a safety issue that should not be made light of in any way.

As for the performance of equipment, if you can not tell the difference in the performance and the plug is polarized then I would look for another issue in the system such as damage. The basic question becomes, when the power wiring is correct, where is the weak link.