I'm intrigued by all of these comments on dedicated grounds for your stereo.
In North America, the house ground is used only when there is a fault, and the current flows to ground as a safety measure. There is never any current flowing to ground in a "normal" scenario. Therefore, installing a dedicated ground for your stereo is utterly useless.
The only time that the ground is used for current in North America is when you're on a farm. We run only a single wire into most farms. The wire goes to the transformer pole in the yard, where it's connected to ground for the return circuit. I spent a summer testing 1300+ grounds of this type. On the other side of the transformer, the feed to the house is exactly the same as it would be in any city. There is a ground at the house for safety purposes, just like in the city.
The only difference between farm and city is that the potential between the house ground and pole ground on the farm is likely to be closer to equal than in the city, where your house ground and substation ground are potentially far apart. This is a moot point, though, when it comes to stereo use.
Is the electricity system different in the U.K.? Is the house ground actually used as part of the circuit, or is it the same as in North America (i.e. used only to handle faults). If it's the same, then all of this talk of dedicated grounds is pure silliness.
-=> Mike Hanson <=-
Posted on: 20 May 2001 by Martin Payne
Tarkin,
but Naim system are quite susceptible to RF breakthrough.
I have previously received Radio Moscow (??) very clearly through my system - without a tuner connected.
I understand that metal-to-metal connections inside the system / wiring can "rectify" AM signals down into the audio band.
cheers, Martin
Posted on: 20 May 2001 by JeremyB
I expect the dedicated ground arguement to continue..
But the RFI issue can be put to rest, I think. Earth impedance should be irrelevant to this, because if I remember and apply Gauss' theorem correctly the electric field is proportional only to the area enclosed by the go and return currents (whether the interfering current or the interfered-with current). The impedance is not a factor in the equation. Think of co-ax (least RFI) vs loop arial (most RFI). Of course, you can apply the same to 60Hz AC. Just make sure you never have two different earth ground connections to two different connections of your system ground. The earth ground has a very BIG capacity!
The problem with a noisy system signal ground is that the amplifier gain and non zero source impedances conspire to cause this signal to appear at the speaker output. A dedicated ground will not be as noisy as one shared with AC return signals. Again, the impedance to ground is not very important.
Note that "no" ground is still a dedicated ground, it's just not a very good one (and not safe in fault conditions), relying on the capacitance between the system common connection (chassis etc)and the earth or other large conductors.
Jerem
