Eliminating Ground Loops

Posted on Feb 5, 2014

One of the most insidious problems in an audio system is one or more ground loops. They not only cause hum pickup, they can inject interference from electric drills, computer hardware and even AM radio stations. Eliminating them is often not a trivial procedure. Here are the causes of, and cures for, ground loops. Both the preamp and power amp are equipped with 3 wire line cords and 3 prong plugs.

Eliminating Ground Loops
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(Note: this is almost unheard of in home audio equipment. This example is given for illustration purposes only). The green wire in each line cord is connected to the chassis of each unit. The ground prong of each plug connects to the local power ground. The two chassis` are also connected together by the shields of the audio cable. The audio cables are much longer than indicated in the diagram. The shaded area shows the ground loop. As you can see there is a continuous loop from the preamp chassis to the power amp through the audio cable shields, from the power amp through the grounding wire of the line cord to the wall socket, and from the wall socket to the preamp chassis. Every tape deck I have ever bought has come supplied with two stereo audio cables. One goes from the tape output on the preamp to the tape deck input and the other goes from the tape deck`s output to the tape input on the preamp. The separation between the two creates a ground loop as shown by the shaded area in the figure above. The cables are much longer than indicated by the diagram. There are AC magnetic fields everywhere there are power lines. If you live in the country far from any power lines you don`t have any AC fields but how do you run your stereo and computer Even if you were to use your own generator it, and its wiring, would cause AC magnetic fields. Anytime an AC field cuts through a loop there is a current induced. if any part of the...

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