k9yc at audiosystemsgroup.com
Sun Jan 22 10:03:43 PST 2012
On 1/20/2012 3:58 PM, Casey wrote:
> Unfortunately, that will not eliminate ground loops if the power source
> to which all the equipment is plugged into is not also grounded by a
> separate wire to that ground rod and to nothing else. This is called a
> technical ground.
It is also VERY UNSAFE, is a violation of all building codes, and
provides no benefit.
> Otherwise, you will have a difference in potential
> between the house electrical ground and the ground rod for the
> equipment, i.e. ground loop.
A difference in potential exists when all grounds are NOT connected.
The rule, both for safety and best noise immunity (including hum and
buzz and RFI) is really quite simple. You may have as many ground
connections as you like, but they MUST be bonded together, and the
connections should be fat copper, as short as practical.
The concept of a "ground loop" is a fiction. The REAL cause of hum and
buzz from the AC power system are LEAKAGE CURRENTS that are the result
of capacitance between the Phase ("hot") conductor and the green wire
(protective ground). Those leakage currents flow in the green wire, and
the resulting IR drop causes a "buzz" voltage to exist between equipment
plugged into different power outlets, and to equipment that might be
GROUNDED better than, or separately from where the AC power line is
grounded. That difference voltage is greatly reduced by properly
BONDING all those grounds together.
We HEAR that buzz on unbalanced connections between equipment because
their chassis are at different AC voltages (due to the IR drop from
their leakage currents). These are not "ground loops," they are simply
LEAKAGE CURRENTS, and they are added to the signal because they are in
series with the signal.
The concept of a "ground loop" is simply WRONG -- more bonding is
BETTER, and is the SOLUTION, not the cause!
73, Jim Brown K9YC.
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