I agree 100% with mrderrick. What he's basically describing *is a* star ground system. You probably already have most of it established in your house right now. I'm a retired Radio Broadcast Engineer, and I had broadcast towers (that were right next to studio and radio station office buildings) getting struck by lightning at least 12 times a year. Preventing those surges and strikes from blowing up broadcast equipment is the name of the game in broadcasting. That's when a star ground system *really* comes into play, and they are mandatory in broadcast facilities. Those same star ground configurations can however also be applied to home audio systems.
If you really feel the need to make AC earth grounding improvements, I suggest 1) check to make sure everything mrderrick mentioned in his post, you are abiding by, or have incorporated into your AC service. 2) NEVER EVER NEVER(!!) establish a completely separate ground system that is not connected to your AC service entrance panel 3) make sure each AC wall outlet feeding your audio system has a ground wire, fed from the AC breaker box, connected to the outlet's ground/earth terminal 4) if you feel it's necessary, install isolated ground outlets, with a *dedicated isolated* ground wire feeding back to the AC breaker panel 5) add additional ground rods to your already existing outdoor ground rod, or ground rods, and make sure they're ll tied together 6) if you have any, tie all metal rebar building structure to your ground system. I even connect gas pipes to my earth ground systems.
The object is to tie all earth grounds together, preferably at one point (hence the name star ground). I realize we're discussing this to keep our audio system's noise floor as low as possible, but another reason for the star ground, is to keep all grounds at the same ground potential. In some past broadcast facilities, I have seen carbon traces where lightning has arc'd over to a ground of lesser resistance, trying to find a pathway to ground.
