Why power cable effect overall syste sound?

The benefit of power cables is far overrated. The benefit depends on RF EMI contamination present. They can reduce noise, but when people start claiming huge improvements in sound, etc., I get a little skeptical. Use a cable of 10-12ga, and this should not limit the current. Shielding is a plus, and don't forget to notice the size of wire in your transformer, and how long it is, maybe 20-22ga. Also, the unshielded wire in your house, all 75ft. of it. Magic in the last 6 feet??? Just eliminate a bottleneck if one exists. There are other things to spend money with a bigger return in MHO. Good matching with your amp and speakers is far more important, and getting the damping characteristics matched well. Jallen

I think one of the main points missing here is not that cords and cables make no difference, but that people are preoccupied with them and forget room treatment which I find to be far more important, as I think speaker cables are more important, and interconnects being of high importance. A line conditioner is also important especially for digital and SS equipment. And not to forget, the position of the speakers in the room, the listening position, and a host of other things are so important, cable fixes, all the way up and down the chain are used instead of getting the speakers right in the room. Cables should be used to fine tune the system. Using a measuring system, like a mic to evaluate the sound in the room at 1M, and at the listening position will reveal a lot of the room and characteristics. Don't rely of your Ratshack meter, it is rolled below 50Hz, and above 10K. So, don't go and buy another power cord if you are rolled at 10Khz, it is your meter.
If your room and system is right, and all is right and you hear improvements in your power cords, keep them, use them, and stick by what your hear. Your ears are your experience, so be truthful to that.
Personally, I have heard many power cords in different systems, and in some systems there was a difference, others there was not one of significance. The cords evaluated were the best from Shunyata, Cardas, Audioquest, and many others. Each system will have different RF issues, and others. Trust your ears, not the money spent....
Jallen