How does power cord affect a digital frontend?

I know it does too, but I don't understand it. What exactly is going on with different powercords? What are the physics behind how a powercord effects a component. Is it simply that it gets the electricity more easily through better powercords, or does each powercord contribute to/detract from the electricity in some way that effects the sound (greater transparency, larger soundstage, etc)? Are there any guidelines for pairing powercords with components or is it trial and error?

I agree with Tireguy. I notice larger improvements on my front end equipment including the pre. and transport.
I think most tweaks are more significant on the front.

I found even more than the powercord was the power itself & undoubtedly you have read about (or have) dedicated lines with high quality outlets. Someone once made the comment that the powercord was not the last 5' of the electrical chain but the first 5' & should be given the requisite attention. OK, I added on that last part but if the AC is not up to par, nothing you do can fix it.

I agree that short of a big power amp being severely choked with a puny cord, digital gear and / or highly advanced preamps seem to be the most sensitive to changes in AC power delivery.

I changed power cords on my Philips SACD 1000 and noticed what i thought was a huge difference. After changing the cords, my Brother looked at me with a smile on his face and said "you know we're not hearing that. It's all psycho-acoustics, right?". Swapping back and forth between the two power cords and charting the system's frequency response using test tones verified that there were not only audible differences, but measurable differences.

The weirdest thing about this is that the only real difference between the two cables is how the ground is implimented. Other than that, the two cables use the same identical geometry and materials. Due to the differences in ground wire configuration, this results in an impedance change along the entire length of the cable. Given the fact that the SACD 1000 has NO ground at the IEC jack from the factory, it is not electrically connected to ground. Just altering the impedance of the AC cord was enough to alter the frequency response of the player. This tells me that this player is WAY under-designed in the power supply. But then again, what digital gear isn't ? Sean
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Ok, it's clear that if a design of the power supply is flawed, it may be easely affected by anything. But what about manufacturers that are proud about their power supply design, such as MF, Simaudio, and others? It seems that under normal circumstances properly designed power supply is supposed to be quite immune to AC quality...