Why do AC cords make so much difference?

Baloney - there is no requirement for an earth ground. There is no "shunting" of noise necessary unless the power supply is letting power line HF noise through - this is unlikely. My transport has no earth ground and it is superb.

Digital is NOT an audio signal at it's point of origin or when being transferred in digital form. It is an RF based signal that operates above 3 MHz. As such, a design that makes use of some type of bandpass, high pass or low pass filtering or has bypass caps in the design may require a low resistance Earth ground for optimum operation. The reason that a designer would shunt such signals to ground would be to try to keep stray signals from "leaking out" or interfering with other sections of the player. While the device would still "work" without having a low resistance path to ground, it might not be performing up to snuff or meet spectral purity as documented by the FCC in terms of spurious emmissions / interference. As such, not all designs are the same when it comes to grounding, nor should they be treated as such. Sean
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Great post, Sean. Thanks.

I am sure that others will offer reasons that I will not have covered, but these are very good starters.

1. The original cable you were using prior to the switch was very poorly constructed and/or of a very high gauge wire for power supply use.

2. You have some form of electrical interference and the better shielding is helping with the problem.

3. There may be a problem with the way the power supply was designed in the equipment you are switching power cables with.

4. You are convinced that a difference will take place and therefore it does.

Let me know if these heip.