And here is the updated piece on misconceptions: https://shunyata.com/2016/06/27/power-cord-misconceptions/
MISCONCEPTION #3: There is up to a hundred feet of wire in the walls, so the last 6 feet of power cord can’t possibly make any difference.
Answer: The PC is NOT the last 6 feet as stated in #1 and the local current and EM effects directly affect the sonic performance of the component. The power cord is not the last 6 feet, it is the first 6 feet from the perspective of the component. The further a noise source is from a component, the less of an impact it will have on the components power supply. The high-frequency noise sources that have the greatest impact on audio and video performance are the system components themselves — which are usually all in close proximity of one another and all emit radiated fields of high-frequency noise. A well designed power cord can act as a noise-isolated extension of the primary winding of a component’s power supply and will help isolate the power supply from the fields of radiated RF and EM noise energy that is ever present in all electronics systems.