The premium outlet (like PS Audio's PowerPort) that I am using does make a big difference. In fact, it was one of the best upgrade I have ever made in my audio life. I am not an engineer. I can't explain why.
If you were an engineer you wouldn't be able to explain why either. At least based on generally recognized science.
You are not improving the quality of the electricity coming out of the wall . You are improving the connection to it
This is what is well put, not the reference to outlets serving as filters and cleaning things up (which they don't).
And of course improving the connection will only help if the original connection is somehow deficient, and if the deficiency is somehow great enough to affect the signal path despite the filtering and isolation which the power supply of each component provides between the ac and the signal path.
Disclaimer: I have not tried any audiophile-grade outlets, so I express no conclusion about them, just a lot of skepticism.
Regards,
-- Al