Knownothing,
>>>"In some ways, it doesn't so much matter what is going on with the many feet of unshielded cable in your walls as long as you are effectively dealing with radiation, interference and noise potentially present in the area directly behind your equipment."<<<
That is essentially true. Improving the wire quality, gauge, isolation and connections between your panel and the wall outlet will render a noticeable improvement in most any system, but nowhere near the improvement *possible* as you move closer to electronics.
Too many people labor under the misconception that components sit at the end of an electrical "hose" and AC pours in like water carrying AC noise and garbage with it. The reality is that components sit between the hot and neutral poles of AC that are rapidly alternating current impulses. Noise that comes from outside the home is minimal and has almost no impact on system resolution compared to system generated and shared noise. Its still a good idea to have system protection from natural weather events or grid surge problems but even these in most cases are over rated. Electronics themselves have built in power filtration that will knock down common spikes and surges that are external to the system.
The bridge rectifiers or switching supplies in electronics--especially within amps and digital transports are often the main culprits in emitting ultra high-frequency noise both as a back-wave and a radiation pattern that surround electronics like a halo and race back through ground. Whatever can be done to mitigate that noise nearest its inception will often net the most obvious results. Obviously, nothing with AC is simple or insensitive so connections, terminations, resistance, reactance, impedance, shielding, geometry and wire type and quality can all play roles in shaping a final outcome.
Of course this is all a process and no one has all the answers. This is more of a readers digest version of what goes on based on experience.
I would never put PC's ahead of room treatment, electronics selection, speaker interface etc etc. However, when viewed as a system rather than as a single PC add on aftermarket tweak to be compared one at a time, replacing power cords in any stock PC system will render fairly irrefutable results in terms of a plainly audible difference. Whether that's good bad or otherwise is in the eye or ear of the beholder.
For those that don't believe their ears, replacing a stock PC on any top quality flat screen like a Pioneer Elite with a good shielded power cord will also render an immediate, hard to ignore result. FWIW.
Grant
