New expensive power cord for amp and no change in sound?

Should have called the cable company.    Try before you buy!

                                              EXACTLY!

        There are also a number of other cable manufacturers and purveyors that allow a listening period and return policy, if you are dissatisfied/unimpressed. 
         ie:  Synergistic Research has offered a liberal audition period since the early Eighties.      Matter of fact: they offered to send their entire line of interconnects, for one to audition/experiment with, before they made their choice and purchase decision.

                                               And (again):

          Anyone that feels compelled to harp on not hearing any differences, is obviously too obtuse to understand the term "variables" (as frequently mentioned) and worthy of disregard.  

          My only goal in these threads has ever been to encourage those with a mind to experiment with their systems, based on the latest (20th/21st Century's) findings of ACTUAL Physics/science and ignore the Cargo Cult's incessant runway building (objections, convolutions, deflections and obfuscations).

                                                Happy listening!

@zlone Depends on how your system is balanced (lean, warm, bright?), sound characteristics you’re looking for and budget. Not to high jack this thread, may be start a new discussion? Or pm me. 

@rodman99999 

+1.

Trust your ears. There are many PC review videos. Don’t trust reviewer’s ears. Listen to the recording of the actual PC. Comparison videos are better. Microphones don’t lie. Human ears are biased always and they trick us. If I like A sound better than B sound in a comparison video, I like A sound better in real life too. Alex/WTA

Not buying it. The voltage drop across a few feet of power cable can't be more than a volt. This is insignificant compared to the normal variability of the supply fluctuations between 114 and 126 VAC.

@noromance I've measured over 2 Volts, but that was on a class A triode amp that made 140 Watts... or it did if the AC was right. When the spec line Voltage was at 120V the amp only made 100 Watts. The measured AC line Voltage at the IEC connection was closer to 117V as opposed to the Voltage at the outlet. A 40 Watt loss is not only very measurable but also audible.

As I said earlier, the power draw from the line is an important aspect of what you can hear and measure. Internal power supply regulation as well as feedback to allow the amp (or preamp) to reject effects of AC line Voltage have an effect as well. So some people will hear things and others will not.

This also explains why many people report better sound at night (which the AC line Voltage tends to be higher).