How come a power cable changes the sound?

if you want to test an expensive power cable be SURE you can return it - and then use a double blind test

insulting people that DO hear a difference is less than helpful, but people that think they hear a difference are highly likely to be victims of confirmation bias and are insulting everyone else

writing about speculative notions as to why something could possibly sound different is of use only to engineers who want to test those hypotheses - not to consumers

cognitive psychologists have clearly established the effects of visual and other biases on sensory perception - either guard against that or waste your money

Rayleigh scattering causes the sky to appear blue

power cables should not affect your sound
- if you think they do, try some blind testing
- if they really do, a real moron designed your amp