Why do AC cords make so much difference?

Audioengr,
I love your calculations and I think your intentions are good, but unfortunately -

1) Capacitor banks in power supplies are designed to handle transients at peak power levels. At normal listening levels only a fraction of that capacity is used. I agree that peak transients at full volume might distort due to voltage sag on the power rails, but I would be more worried about hearing loss than distortion in this case.

2) The AC power in the U.S is 60HZ, not 20KHz. (Duh...) If you are worried about a 20KHz component getting into the signal path through the power cord, then you would want a power cord with higher capacitance to filter it out. Any amplifier that doesn't have adequate bypass and isolation in the power supply shouldn't be in your system in the first place... so any power cord that results in an audible improvement would be a band-aid rather than a fix to the root cause of the problem.

To be fair, I should say that there are probably homes out there with enormous amounts of noise on the AC power. While replacing the power cords to all of your equipment could conceivably make a difference, the proper remedy would be to install a power filter/conditioner.

I'm another guy thinking the cords act as a band pass filter. A couple of years ago i read an article about using home electric wiring as the house computer network as well. The network signal was designed to operate at a higher frequency outside of the "noise band" on the power cable. high end power cords are likely to act the same way. THe question i have, however, is once you get rid of the crap on the power signal and you are setting with a pure 110 ac current why should there be a tonal effect. Bwhite has some interesting thoughts but i would think that the magnetic field of a large power transformer would overwhelm the effect of a magnetic field in the power chord. the lower inductance arguement stands up well for amps but for a low draw component like a cd player?? On the positive side the mystery gives the ole brain something to feed on

Piezo: Your comments about low inductance to Audioengr are something that i've tried to stress to him in other posts. It is not so much the low inductance than can be helpful in low current demands as it can be the added capacitance that many such designs bring with them. If someone doubts the effectiveness of added capacitance, try sticking an AC rated cap into an outlet and measure / view the differences in the power provided at that outlet.

Redbeard brings up added capacitance in his post ( rightly so ) and also touches on the lack of filtering in components making the differences in power cords being noticeable. I agree with him whole-heartedly in this respect and am glad to see that someone else shares this view. Most products are NOT properly filtered, regardless of price paid or brand name "prestige", and that is why one can hear the differences with various AC delivery systems. The only problem with Redbeard's suggestion to install a power line filter / conditioner to remedy such problems is that they too are mostly under-engineered and end up being a "band-aid" rather than a "cure-all". As such, poorly designed filter based products can bring with them almost as many side effects / problems that they try to solve. Sean
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Redbeard - I suggest you measure the current in your power cords. I suspect that you will find spectral components higher than 20 kHz. Current, not Voltage ...Duh. Unless you have an expensive power supply that is designed properly in your component, this will always be the case.

Also, I recommend strongly against filtering, except on the ground lead to eliminate ground-loop currents.

I do not buy the capacitance argument. My cords add only a few hundred pF of capacitance, yet they are 10X lower inductance than the ROMEX in the wall. Until you have heard a really low inductance cord for yourself, you cannot know what the improvements are.