I agree with sedluk.

The only thing left for that last few feet is shielding. And it really doesn't take that much expense to shield the last 6 feet of power and their shild not be that much variation in shielding. The shield would only effect other cables that are also poorly shielded picking up the Electro-Magnetic Interference.

Now if you're running a power conditioner the argument of putting a better cable on the last 6 ft is no longer valid.

Are you running power conditioners and how did you test the difference?

Don't under estimate the power of suggestion that something is better.

Take this for example:

http://www.fda.gov/fdac/features/2000/100_heal.html

- Fiddler (IMHO)

If you think listening to music is fun, try learning an instrument.
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