[Eeyore]

robert casey wrote:

Eeyore wrote:

And how again does it reduce hum ?

The shield on the power cord would reduce the *electrostatic* leakage
from the cord.

Into the shield of the interconnect. Not into the signal conductor. A few microamps
(if as much as that) in the shield are going to do sweet bugger all.


It won't reduce *electromagnetic* leakage, but the fact
that the currents on both current carrying conductors in the cord should
cancel, to cancel that out.

Only if there's tightly twisted which most certainly they aren't.


What difference would the proximity of lots of screened unbalanced signals make

Every dB of reduction of hum you can get from the shielded power cable,
and from the patch cords ("interconnects") helps. If you have a system
that would normally have 120dB S/N.

I don't think you're going to find any system that can do that.


Now, if you want to listen to AM
radio or some scratchy vinyl (because you like the programming, and it's
not available on a lower noise source), then the shielded power cord
probably won't be noticed.

The point you're making is one of masking effect which is valid. However I've yet to
hear any interconnect hum simply by bring a live but non-current carrying mains lead
near it.


Shielded power cords have a valid reason to exist, unlike those wooden
knobs for the volume control of your amp, that supposedly makes for
smoother sound. Or the speaker cable supports to prop them off the floor.

The only valid reason I can think of is for IT equipment to meet regulatory
requirements, not for any perceived or real benefit to hi-fi.

Graham