Can a power cord increase the resolution of an Class D (SMPS) amp by more than 5% ?

In the US the "signal" would be a 60hz sign wave and at 120v

The concept of a dielectric conducting any signal in the audible spectrum of 20-20hz is ridiculous 

As frequency increases, the Dielectric starts exhibiting shunt resistive losses which can be measured and quantified as signal loss across the termination load. Fortunately for our application (audio) these shunt losses don't begin to surface until frequencies much higher than the audio bandwidth.

The concept of a dielectric conducting any signal in the audible spectrum of 20-20hz is ridiculous

What I said is that the electromagnetic wave associated with a current propagates essentially outside of the conductor, and therefore propagates via the dielectric. I was NOT saying that the "current" itself, as conventionally thought of in terms of the movement of electrons, is conducted by the dielectric. Please re-read my posts and also the Wikipedia writeups I referenced.

Regards,
-- Al

Above I said:

The electrons that move back and forth at certain frequencies (as determined by current voltage and resistance) in an AC current as a result of the EM wave does.  

In that post I meant to say

The electrons that move back and forth at certain frequencies (as determined by current voltage and resistance) in an AC circuit as a result of the EM wave does

AC circuit, not current.

IMHO, I have never heard any audible difference using "directional" cables ever. Knowledgeable manufacturers (Belden, Canare, etc) don't put arrows on their cables because those products are not directional.
There is one good indication for those arrows, it means one should probably not purchase those products.

Hi Zuio,
 Your question of " Can a power cord increase the resolution of an Class D (SMPS) amp by more than 5% ?" I would say "no". Your question involves much more than an AC power cord. One needs to look at the entire "chain" of components used. Chasing your "5%" by changing AC cables will only drain your wallet.