How can power cords make a difference?

Funny story I am progressing through right now. A friend of mine(a guitar player) is recording a CD with his band. I expect it to be big. Don't be surprised if this band bursts on the scene big time. I asked him if he could try out a power cord with his Mesa Boogie, so the CD could sound its best. I gave it to him a little over a week before the recording session. He called the next day to say that the cord made an improvement in his sound. Not night and day, but meaningful. Subtle. He recorded, and all went well. He then reinserted his stock cord. After a day or two, he just wasn't happy with his sound. Was it this, that, or the other thing? Was it the mood? Was it him? He couldn't figure it out. Then, he reinserted the cord I gave him. Everything instantly snapped back into the way it should be. It was the cord! A little later, a recording engineer commented on his sound. He asked about the equipment, and looked it over. Nothing seemed any different than anything else he's ever come across. He asked if the amp was hot rodded or whatever. He commented that he couldn't believe the sound coming out of his amp. My friend then told him about the cord. My friend then returned the cord to me, and I gave him another to try. His remarks to me were that he cannot live without a good power cord. He no longer sees the difference as subtle. His impressions are now concrete. Now he NEEDS a power cord. Are we going to start a revolution in pro audio???

Trelja: I have the HT IEC adapter on it's way for my Pioneer CD burner. I will try upgrading the power cord for the analog to digital copies that I will be making. Upgraded PC's have worked on everything so far with the exception of my tube amp (which seems to be impartial) and we'll see if it improves the quality of the copies. I will also check to see if it makes a difference on digital to digital copies as well.

All a power cord has to do is deliver AC energy to the audio or any other kind of device's power supply. The more current the device needs, the larger the conductors in the cord should be. Thus a 120VAC power amp might benefit from a 14 or 12 gauge cable, while a CD player would typically only need an 18 gauge cable. There is no audio signal going through the power cord, and the supply itself isolates--or it damn well should, if any sort of competent person designed it--the audio circuitry from the AC and the power cord. Fortunately, cables are a commodity item, so there are inexpensive ones for those who want performance at a low price, and there are expensive ones for those who want performance at a high price.

70242.241. So are you inferring that the stock power cord on my new Sony 9000 ES, which was an 18 gauge, is sufficient enough that replacing it with a high quality power cord ( 12 gauge?) from Purist Audio will not affect the performance?

Albert - There is literally no conceivable reason why your Sony DVD player should benefit from a 12 gauge line cord. If your Purist cord does improve the sound it is because of some phenomenon outside the known laws of science. It is very similar to someone claiming that their car runs better when the gas is pumped thru certain brands of pump nozzels.