Interesting that you have noise only
in your center channel. You may be right that there's an issue with the internal cable routing or designs. The powerbridge itself is not likely the cause but where and how it's connected could very well be.
There's a lot of very electrically noisy poorly designed electrical items in our homes. Many are familiar with noisy dimmers because they audibly buzz, but when you look at their electrical output, it is horrible. Highly quality dimmers cost more and some manufacturers are better than others. Where's this going? I have an X10 system in my home which is very
sensitive to power-line noise.
You would be shocked at the things X10ers have found which generate noise throughout the electrical system. Things like fluorescent lamps, poor quality LED bulbs, most computer power supplies, cheap phone chargers and even LED nightlights. Having been dealing with this for quite a few years, now when something new comes into the house, I test it against my noise meter. If it generates noise, it either gets a filter block on it or it is returned.
This is one of my biggest concerns with subs distributed around the room and why I'm trying super hard not to do that. Why? Because each may be plugged into a different power circuit - which bypasses my main AV electrical setups.
So far, I've never even had a hint of a ground loop or any noise enter the AV system with this single point ground design
. It's ultra-dead quiet.
I recommend considering unplugging all the little items you may have have around the room or on these circuits. Even things that look innocent like a night light or LED lighting or especially computers which contain switching power supplies or UPSes - some of the worse offenders. As a troubleshooting step, maybe switch off all the circuits in your house at the breaker panel except the ones driving your AVR setup.. then check it again. Then methodically switch each one on one by one. You may find something introducing gobs of noise into your setup which is being picked up but generated elsewhere. For UPSes and computers, you really need to pull their cord from the wall while you are testing because they inject gobs of noise when they are operating online or charging. Also in your AV setups with non-polarized circuits, simply try flipping the plug in the socket. Sounds craze but there's some science behind why it can have impacts - depending on the power supply designs in the equipment.
> Anything with a switching PSU (most computers) is likely to be very electrically noisy unless the designers paid attention to backwash. Local filters may be needed to block that noise from entering the circuits. It is ideal to connect all the key components into the same set of power outlets. I prefer to use SurgeX units though some people prefer to use simple power strips with no MOV and other extras.
Just another angle to help consider options, the root causes of the "noise" and maybe a good solution
Additional recommended reading from a commercial vantage -> https://www.middleatlantic.com/-/med...ack.ashx?la=en
I hope this helps with the ground loops - peace.