I initially believed cables made a difference. Then decided it was mostly marketing because I could not really hear any appreciable difference. And then over time, while improving my listening abilities, was fortunate to have a truly well made speaker cable in my system for a week, and a well made power cable in shortly after that.
And now I am comfortable having every belief I have questioned, because what I may not be able to hear does not preclude its existence.
How arrogant it would be for me to believe otherwise.
And the single biggest change to my belief system was coming to understand that the boxes matter less than how they are brought together with everything else that supplies and most especially, grounds power.
In friendship - kevin

