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Ground Loops

What is a Ground Loop?

Ground loops are a main cause of noise, hum, and interference in audio, video, and computer systems. Wiring practices that protect against ground loops include ensuring that all affected signal circuits are referenced to the same point as ground.

A ground loop is the connection of multiple devices that result in a number of different paths to ground the equipment. For example, two devices being connected using a standard 3 prong (positive-neutral-ground) power cable. This can be a problem when there are other data cables being connected between the original two devices, typically for audio and data transfer. The shield of the connecting cable is usually tied to the ground of each unit, closing the loop with the power cords, which is then connected to the structure of the building’s ground wire. This is a ground loop. Differences in the two grounding points can cause frequencies to be heard while not operating the device, playing any audio, or also caused from the interconnection of data cables.

How to Troubleshoot –

There are a few steps to take to determine where the ground loop frequency is occurring:

  1. Power off all connected devices and disconnect all interconnected items to the suspected device.
  2. Power on the device in which the ground loop frequency is occurring. If at start up, the device emits the 50Hz frequency, this may be a sign of a potentially bad ground, to which the device in question is also connected to (change outlets on a different circuit in the house to confirm this).
  3. If no frequency is heard after start up, you will begin connecting 1 device at a time until the frequency is heard (plug into the wall outlet and interconnecting data cables Ex. RCA).
  4. Continue to connect all devices until the frequency is present. (Ex. Monolith amplifier connected to 5 speakers. While powered on, no sound coming from speakers until a blue ray player is introduced. This would indicate the ground loop frequency is caused from the blue ray player.)
  5. Once this has been isolated to a specific device, steps to lift the opposing ground can be taken by using such items as a 2 to 3 prong grounding adapter. This takes the ground of the opposing device and allows all units to share a central ground. This should now alleviate the 50Hz frequency and isolates the issue to the unit that may have a bad ground, where other items such as power conditioners can be used to fix the problem for good.
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