Sorry the EE in me can't let this one go. :-) The magnetic permeability of Copper, of which 99.9% of all shielding is made, is the exactly the same as air, which is one. Copper does not impede magnetic fields. When you add a shield to a cable you increase the capacitance of the cable. The shield acts as a ground plane at a relatively small distance from a current carrying plane separated by a dielectric, hence a capacitor. However in a well executed design, the capacitance introduced by shielding is usually very small. This could be the cause an audible difference, or it could be the cable is doing its job properly and it is letting you hear more "grunge" in the original signal. - Cheers, Dan
