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Old 08-10-2019, 12:20 PM
thompsonbr87's Avatar
thompsonbr87 thompsonbr87 is offline
Join Date: Jul 2015
Location: Smyrna, TN
Posts: 102
Default Whine in headset

After installing a new radio, audio panel, and stereo headset jacks, I have introduced some sort of electrical whine into my audio system. The tone seems to be RPM dependent - high RPM = higher pitch. The whining sound seemed to be intermittent, but there wasn't anything apparent that made it cut in and out. Could be heard through both Lightspeed and Bose headsets in pilot & co-pilot jacks.

Reading some old posts, it sounds like it is likely related to the alternator? Some have fixed their problems by replacing diodes or noise filters (that's getting above my current knowledge level at the moment)? I did all of my own wiring on the upgrade, and I think it is more likely that my inexperience has somehow caused this than rather something failing on the alternator coincidentally.

What else could I be potentially looking for? While researching and learning, I kept reading about ground loops. What does that actually sound like? I am currently under the impression that a ground loop is more of a static sound than a whining sound.
Smyrna, TN - KMQY

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Old 08-10-2019, 02:12 PM
Mike S's Avatar
Mike S Mike S is offline
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Join Date: Sep 2005
Location: Dayton Airpark, NV A34
Posts: 14,765

Sounds like alternator noise.
Mike Starkey
VAF 909

Rv-10, N210LM.

Flying as of 12/4/2010

Phase 1 done, 2/4/2011

Sold after 240+ wonderful hours of flight.

"Flying the airplane is more important than radioing your plight to a person on the ground incapable of understanding or doing anything about it."
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Old 08-10-2019, 02:14 PM
BobTurner BobTurner is offline
Join Date: Dec 2011
Location: Livermore, CA
Posts: 5,805

A ground loop is a likely source of the noise, which is likely from the alternator. What happens is a small amount of the alternator current seeking to get back to the negative battery terminal is running thru the ground wire of an audio cable, inducing a small ac voltage drop that you hear. What you should have is:
1. Separate ground wires for the headphones and mike (not the shield).
2. Standard jacks must be isolated from any airframe metal.
3. Shield should not be connected at the jack (if you did #1).

Look carefully at all jacks for #2. One of the fiber washers must have a shoulder on it to go inside the hole. Sometimes the metal part of the jack is in accidental contact with the airframe. Truth is these problems can be tough to find.
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