Paul Maybury wrote:Hi Chris, strange, I read through the whole thing again and can't find it1
I'll post a question in the DIY section and see if anyone else has a clue or two about this.
Paul
Is this what you where after?
( page 2 of the Technical Interferance Tab on Colin's web page )
2.3 Grounding to reduce Electrostatic Interference
Let's consider the hypothetical example of an amplifier - say a guitar amp - which has has been plugged into the the mains with the "earth" wire disconnected and has no other connections. (I am not seriously suggesting that anyone does this, since this creates a potentially dangerous situation!) There will always be a small amount of leakage between the amplifier mains connections and the amplifier common, due to imperfect insulation of the mains transformer, mains wiring and so on. In addition, some equipment has built in mains filters which consist of small capacitors connected between the mains connections and the amplifier common (which is the metal chassis). These capacitors are supposed to shunt high frequency mains-borne interference to ground and have very little (but still some) effect at mains frequencies.
Normally, this leakage is so small that if we were to touch the amplifier chassis, we would not feel anything. Sometimes the leakage is sufficient to give us a slight tingling sensation. With bad leakage or defective equipment we could get an electric shock.
In Australia, the mains neutral connection is connected to ground and the mains voltage is 240 volts AC at a frequency of 50 Hertz. We can represent this situation with the circuit shown below, where "Active" = 240 volts AC, "Neutral" is ground and the resistors represent the leakage: