We had a request for advice on a guy building a pretty complex AV room in new home construction.
Here is some of the advice I gave him on this issue. Basically this is now a huge subject that actually warrants a text book of several hundred pages. It is a book I probably should write but doubt I will.
Here is what I wrote to him.
You need to properly plan your house grounding and equipment grounding. Earth loops that create hum and buzz are the curse of AV systems. With all the channels now this becomes of primary importance. A buzz formerly hardy heard on a two channel system becomes a roar with 11 channels and a sub or two doing it.
Ground loops are caused by resistances between grounds.
Now local electrical codes vary. Some require a ground to the water system and grounding rods. This sets you up for trouble right away.
Fortunately here in Eagan a ground to the water supply is all that is required. One ground is good, more, trouble.
So I supervised a massive cable to the water entry and then a massive cable to the panel. There are two panels a main and a large sub distribution panel. The panels are opposite sides of the same wall. Again these are linked with a large braided copper cable.
The racks in the chase are all linked with heavy copper cable and bonded with it back to the panel. The plug mold on the rack was bonded to the racks as was also the Comcast cable.
Now cable and satellite systems are a particular problem. They seem to come with inherent ground loops and despite good practice and following code, which I supervised there was a very low level buzz with the Comcast TV box connected. So I did have to isolate this ground with transformer. After that all 18 amp channels and the 11 speakers are dead quiet.
So pay attention to your grounding plan and ground plane.
Another issue is to make sure you use big enough gauge wire commensurate with your speaker impedance and length of the runs. I suspect you will have long runs and if so recommend 10 AWG Belden cable available from parts express. My AV room has 600 ft of this cable in conduit.
If you have HDMI runs longer than 25 feet, you will need either a boosted cable or a hybrid optical copper one. I recommend the later although more expensive. I also advise powering the cables from and external supply and not from the HDMI port.
This is the issues I can think of for now, but I suspect there are others.
Yes, there is one other issue I omitted to warn you about, and that is LED light bulbs and dimmers.
LED light bulbs and especially the dimmers radiate a lot of RF interference, which is another potent source of buzzing in AV systems.
Now you want to specify Lutron Maestro dimmers. These have the lowest RF emissions by far. Having said that keep the wiring off each dimmer limited. I did not allow lighting circuits to be shared with wall outlets. As far as possible I kept each dimmer on its own circuit.
Despite that I still had one issue. Some LEDs interfere with each other.
There are three LED fixtures on our stairway. On the other side of the landing dimmer was the dimmer for the family room lights. They were on the same circuit. Well when the stair lights and family room lights were both on, the family room lights flashed, the dimmers emitted noise right out of the switches and the RF really created a buzz in the studio. After a Google search I found this was a known issue with some LED combinations on the same circuit. We could only solve it by fishing another circuit from the panel so the stair and family room light were on different circuits. Then we had peace and quiet.
In the meantime it would be really helpful to me if I knew that date your house was constructed. This will have big impact on what I have to say and he lengths you may have to go to to solve the problem.
