Robbyg, Stuartbranson, Tbg:
Robbyg: The reason one makes the measurements with the component off, and all input/output connections detached is because what your trying to determine is how all the component's various circuits "grounds" combine and where that total is positioned electrically -- i.e is it closer to the "hot" blade of the power cord or the "neutral" blade of the power cord. Depending which way the blades of your equipment's power cord are oriented relative to the real "Hot" and "Neutral" of the electrical service in your wall, you'll get a bigger potential difference or "leak" in one position or the other. The position with the smallest leak will give you the least hum in your system when the component is finally turned on.
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Stuartbranson: You little devil!! Of course you could, but what about when you start to get oldtimers disease like me, and forget what you did where. Or what if someone buys your house and can't understand why they keep getting shocks from their vacuum cleaner!!
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Tbg: Soooo....you like a little electrical stimulation once in a while, do you?! "Higher leakage voltage" indeed! Listen: Audiophiles are a dying breed, so please be careful, we need you. If you find yourself craving higher and higher leakage voltages, please, email one of us before it's too late, your body fries your computer and you lose all contact with the outside world!
Neil
