You’ve all heard it, the dreaded 60 Hz buzz through the speakers of a home theater or home audio system. I hope you heard it from a friend and not from you. It can make you completely crazy. You may have even tried, without success, to solve the little noise problem. It can make you even crazier. What is causing this horrible noise through your speakers?
Most often, the hum of your speakers is caused by a grounding problem. There are three main grounding problems that cause problems in an audio / video system. These are ground loops, improper grounding, and complete lack of grounding. Other possible culprits that can cause noise are bad cables, faulty equipment, or electrical noise from a dimmer or electric motor. There are steps you can take to resolve the noise and eliminate it from your cinema.
The first step is to find out where it comes from. Disconnect your source and display equipment from your surround sound receiver or processor. If the noise stops, reconnect them to the receiver or processor until the noise returns. When the buzz comes back, you have found where the noise enters your system. Note that if you connect remote equipment, such as signal transfer from your movie theater DVD player to the bedroom TV, your chances of picking up noise increase considerably. With such lengths, noise can be induced in long cables from adjacent electrical wiring. It is also easy to create a ground loop, since the equipment is connected to two different and largely separate sockets, on different electrical circuits.
If the noise is caused by a cable box, the noise is most likely caused by the grounding of the cable TV. To test this theory, disconnect power from the incoming cable TV on the back of the cable box or TV while they are still connected to the rest of the system. If the noise is eliminated by unplugging the cable from the TV, the problem is grounding the cable. You can electrically decouple cable TV power from your system with a revolutionary transformer. This information is available from many sources. Be aware that many newer digital cable TV systems require that any device in the signal chain pass above 1000 MHz. Some of the older grounding transformers will not. Be sure to check the specifications of the device you purchase to verify that it will pass the digital cable TV signal.
If the noise is coming from your projector, television or monitor, it is probably due to the fact that the video display device is connected to a different socket from that of other audiovisual equipment. It could also be on a different circuit. These circuits can have two different ground potentials. In other words, the resistance to earth is different on each circuit. A difference in earth resistance from one point to earth can cause the dreaded earth loop. If you get a ground loop, the current flows between the two components. If the current flows through the ground of the internal audio signal of the components, you will get a humming noise.
You can use an isolation transformer, similar to the type used for cable TV grounding problems, to eliminate the electrical connection from one component to another. These transformers are inserted in line with the audio signal connection between the two components. If there is no audio connection between the components, the problem can come from the current flowing through the video part. In this case, a video isolation transformer should be used to eliminate the ground loop.
Sometimes power conditioners stop noise problems by placing equipment on different electrically isolated outlets. This is done using isolation transformers. Sometimes this is ineffective, however, due to differences in the internal construction of different power conditioning equipment. Some safety regulations, such as UL 1950, specify that an isolation transformer is only allowed to insulate hot and neutral wires; the ground wire must be passed directly through. If this is the case, the problem of the ground loop can still exist because many communication circuits are connected to the grounding conductor and not to neutral. In this case, the isolation transformer, or any power conditioner or UPS with an isolation transformer will have absolutely no effect on the grounding problem.
Noise can be generated from outside, from a dimmer or refrigerator compressor, for example, and from the main power input of audio video equipment. In this case, a high quality power conditioner can be effective in reducing or eliminating the noise problem. You may also find that one of the signal interconnect cables in your system is faulty. It can also cause noise problems. Check this by replacing the cables with one that you know is good.
You can solve most noise problems in your home theater or multi-room audio / video system by taking a systematic, step-by-step approach. Progress through the signal chain, eliminating each piece of equipment as you go. If you have nothing connected to your speakers except the speaker wiring and they are still buzzing, the problem is the noise induced in the speaker wiring by the adjacent power cables. Apart from this case, most of the problems are caused by ground problems, which you can find and solve if you do it step by step.
Source by Steve Faber