You have just finally set up your very own home theatre. You have decided to have a hybrid setup, a combination of a customized as well as a home theatre in a box, where you had actually made a few tweaks with the customized system setup specified and added a couple of devices as well as installed a better cable to connect all devices together. Once everything has been setup, and you thought that everything have been fixed securely, you decide it’s time to test the system. After plugging the power and turning on the TV set, you stretched on the sofa in front of the big screen. You were anticipating that you could enjoy the time watching a movie (you have just bought a DVD earlier just for this purpose) and rest for a while after a couple of hours working to have the system up and running. To your dismay, you see a succession of faint lines that continuously rise up the video display screen. Then, the speaker started to project a high frequency noise. Surprised, you automatically turn off the system. Then you turn it on again, after checking all other connectors are in place. After several attempts to solve the problem, which by now you know is called a ground and a hum loop is, you decided a friend whom you know is knowledgeable in troubleshooting similar problems. He came in just in time you are already on the verge of losing your temper and explains the why’s and how’s of this common home theatre setup problem.
After a lengthy discussion with your friend about your current concern, you were made aware that ground loops occur when two or even more devices are coupled to a common ground through different paths. Currents that flow through these multiple paths acquire energies that can cause damage, noise or a 50-Hz and 60-Hz hum in your audio or video equipment.
To avoid ground loops, every single signal grounds need to flow through one common point. But if two grounding points cannot be avoided, one must separate the signal and grounds from the other.
It’s important to point out at this point that a perfect or “quiet” ground is not really possible to establish or gain. In theory, the reason behind this is that the grounding electrode conductor is a long wire between two different points. And as the distance between the wires increases, so does the possibility that more noise will be gathered.
How then can these be eliminated?
There are a number of ways to eliminate sound and video hum in a home theater system. You need to make sure at first that the cable grounding block is well grounded to the service ground, and not just to a nearby water pipe. If it appears grounded properly then, check if you can plug the entire system into the same outlet. This is normally, all that is needed since all the ground connections are directed to the same point.
However, if it’s not feasible, especially for larger home theatre systems, you can alternatively use special ground breaking devices, like a ground isolator (this can transfer a signal across an electrically insulated barrier, i.e an RF ground breaker). You may also consider using a transformer as it can serve as an exceptionally efficient ground isolator.
To know how to properly setup your home theatre system, check out this home theatre installation video.