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By Steve Faber You have all heard it, that dreaded 60Hz hum through the speakers of a home cinema or house audio system. Hopefully you heard it at a friends house and not your own. It can drive you completely nuts. You may have even tried, unsuccessfully, to fix the little noise problem. That can make you even more crazy. What causes that horrendous noise through your speakers? More often than not, humming through your speakers is caused by a grounding problem. There are three main ground problems that cause problems in an audio/video system. These are ground loops, improper grounding and lack of a ground altogether. |
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The other possible culprits that can cause noise are bad cables, a faulty piece of equipment or electrical noise from a lighting dimmer or electric motor. There are steps you can take to troubleshoot the noise and eliminate it from your theater | |
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The first step is find out where it is coming from. Disconnect your source and display equipment from your receiver or surround sound processor. If the noise stops, connect them back to the receiver or processor one at a time until the noise returns. When the hum comes back, you found where the noise is entering your system. Note that if you are connecting remote equipment, such as running the signal from your theater room DVD player to the TV in the bedroom, your chances to pick up noise increase dramatically. With such long runs, noise can be induced into the long cable runs from adjacent electrical wiring. It is also easy to create a ground loop, because the equipment is plugged into two different, widely separated outlets, on different electrical circuits. |
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If the noise is caused by a cable box, the noise is likely caused by the cable TV ground. To test this theory, disconnect the incoming cable TV feed to the rear of the cable box or TV while they are still connected to the rest of the system. If the noise is eliminated by disconnecting the TV cable, the problem is the cable TV ground. You can electrically decouple the cable TV feed from your system with a ground breaking transformer. These are available from many sources. Be advised that many newer, digital cable TV systems require any device in the signal chain to pass a full 1,000 Mhz. Some of the older ground break transformers will not do this. Be sure to check the specifications of whatever device you are purchasing to verify it will pass the digital cable TV signal. If the noise is from your projector, TV, or monitor, it is most likely caused because the video display device is plugged into a different outlet than the other a/v equipment. It could be on a different circuit as well. These circuits may have two different ground potentials. That is, the resistance to ground is different on each circuit. A difference in resistance to ground from one ground point to another can cause the dreaded ground loop. If you get a ground loop, current flows between the two components. If the current flows through the components internal audio signal ground, you will get a hum.
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 Krank Up The Volume With Home Cinema Speakers
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