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How to Eliminate Hum or Buzz

How to Eliminate Hum or Buzz

The Ground Rules

Of all the annoyances that can afflict any audio/video home theater or even a simple stereo installation, the notorious “ground loop” may well be the most difficult and persistent one to track down and eliminate. A “ground loop” is caused by the difference in electrical potential at different grounding points in an audio/video system. (All the grounds in an A/V system should ideally be at “0” potential.) A ground loop typically adds a loud low-frequency hum or buzz as soon as you plug in any of various audio or video components, including subwoofers, cable-TV outboard boxes, satellite-TV feeds, TV displays, amplifiers, A/V receivers or turntables. The buzz/hum is a byproduct of the multiple power supply cables and a ground voltage differential within your system and its network of interconnecting cables.

Here are some methods to help you get rid of ground loops. Try these first and don’t waste money on a power “conditioner” which, in most cases, won’t help.(There is no need to “condition” the AC power for your system. Your receiver or amplifier already has a power supply with its own filters and transformers. No further filtering is normally required.)

  • If you get your system up and running and hear an audible buzz or hum, the first culprit to look at is either the powered subwoofer or your cable-TV or satellite-box feed at the entry point to your system.
  • First, the subwoofer: unplug the coaxial cable that connects to your powered subwoofer to see if the ground-loop hum disappears. If it does, it’s likely coming in through your cable/satellite TV feed.
  • Reconnect your subwoofer’s coaxial cable from the subwoofer input to your receiver’s subwoofer output and disconnect the cable-TV feed (or satellite feed) from your outboard set-top cable box or satellite tuner. Be sure and disconnect the cable before any splitters. Now see if the hum/buzz from your subwoofer stops.

If that eliminates the hum, you can install an inexpensive in-line ground isolators like this from Amazon. Note that these transformer-based ground isolators will work fine with analog cable-TV feeds, but depending on their design they may interfere with or block reception of HDTV signals via a digital cable or satellite dish feed.

Install the ground isolator between the cable-TV feed and the input of your outboard cable-TV box or satellite tuner (or the TV display’s antenna or cable input if you have a set with a built-in TV tuner or a cable-card ready set). In many cases, the ground isolator will “break” the loop and remove the annoying hum or buzz by isolating the TV-cable ground.

If a hum remains with the TV cable completely disconnected from your system, or you don’t want to risk degrading reception of HD signals from a cable or satellite system, then you may have to add a RCA ground isolator like these from Amazon or Crutchfield between the line-level coaxial subwoofer cable from your A/V receiver and the line-level input jack on your powered subwoofer.

In all cases, if your subwoofer has a ground-lift screw like some of Axiom’s subwoofers, try first removing the screw (or replacing it) to see if it increases or eliminates the hum. It may or may not make a difference.

If you do not have easy access to the aforementioned ground isolators, here are a few more tips:

  • Try plugging the subwoofer into a different AC outlet in the room, one that isn’t supplying power to your components (A/V receiver, TV, cable box, etc.). That might fix it.
  • Try reversing the AC plug for your A/V receiver or the powered subwoofer. If it’s a 3-wire plug or a polarized plug, which has one prong wider than the other, you won’t be able to reverse the plug. For safety, do not use a “cheater plug” to bypass the 3-wire plug.
  • With the power OFF, reverse the AC plugs one by one of any other components that have a standard 2-prong AC plug that isn’t polarized. Each time you reverse a plug, turn on the system with the attached component and your subwoofer and see if the hum disappears. In some cases, reversing one or more plugs will eliminate the hum.

If you have a turntable, try connecting a separate ground wire to a chassis screw on your preamp or receiver and see if the hum disappears. If you already have a turntable ground wire, try removing it from the preamp. One or the other may eliminate the hum.

Finally, here is another solution that worked well for a member of our message boards who decided to discard his ground-loop isolator on his subwoofer: “I took off the ground-loop isolator I’d been using and connected a plain 14-gauge wire to chassis screws on the sub and the receiver then powered everything on. Although hum was still there, it was far lower than before. Next I unscrewed the ground-loop screw on the back of the sub and that took care of the hum completely.”

alanalan signature
by Alan Lofft, (bio), Axiom Audio

  • Nobody

    God bless you sir. Your article just solved my ground loop problem. And the sound is now vastly improved. 

  • Paulscales

    i have just bought a ministry of sound tower system and there is a humming also wen the disk begins to play you can hear it louder pls any help will be greatfull thanks 

  • Me

    i tried as hard as could to ellimnate the buzz and hum i was getting to no avail. I tried another subwoofer and no hum. So i concluded i had a bad subwoofer. Was just getting ready to spend $200 on a new one until i thought about using the speaker line inputs from the front speakers. It worked with no hum or buzz. Had to reconfigure my home theater a bit buti saved myself $200. I guess my RCA input was bad. So when you’ve tried everything, dont count out a bad subwoofer.

  • Johann Iceland

    My setup is 5.1 using Yamaha RXV371BL amp with an inactive out for a subwoofer and an old amplifier between the Yamaha and my inactive subwoofer:
    I tried lots of things to eliminate the buzz from my subwoofer.#1 Cleaned the old amplifier, blowing out dust and cleaning contacts and knobs with alcohol spray.  Got rid of the crackling in the volume knob, but still had buzz.#2 Connected the old amp on a seperate ac outlet (seperate branch).  Still buzzin.#3 Changed the cable between the amps to coaxial.  Still buzzin.
    and the solution:#4 Connected the minus input on the old amp to the chassis of the amp and thus earthing it! The buzz vanished completely.  See attached image! The image shows the back of the old amp, the black wire is from the minus on the input to a screw on the back, the screw gives earth connection to the amp.  (the screw happens to be a part of an other input plug…but that is irrelevant).

  • mcflash

    My problem was sub-woofer hum on a speaker connected to my receiver which I use to play music streamed on my computer which is also connected to the receiver. I bought the Radio Shack 270-054 Ground-Loop Isolator mention in the article (~$20) .  Their instructions tell you not to connect the isolator to speaker or video cables.  What I did was install the isolator between the audio cable from my computer and the receiver.  Hum gone!

  • Robertjmjrs

    I have a Yamaha 5.1 receiver, an Emotiva 5 channel 300 wpc amp, and a Snell 750 w mono sub amp. Last sub amp hummed loudly also(a Peavy). Cable disconnect didn’t work, so used 2 different ground loop isolators. Both seemed to badly degrade the volume and quality of the signal to the sub. I might be able to live with the very low hum on the Snell amp, but the hum is disabling the signal sensing auto off/on feature on the Sub amp. Because of the amount of power the amps can use, I have to use 2 different power circuits. I have tried everything else. There are no grounding screws/lugs on any of the components and I heard somewhere to not try and run wires to connect all the different chassis. I was thinking since this problem is caused by a very slight difference in ground potentials to the components, would it hurt anything to hook together all the round 3rd grounding prongs on all the 3 wire plugs? All of the green grounding wires (as well as all of the white wires) terminate at the same place inside my electrical breaker box. All these wires run to every outlet and I am guessing that either the difference in lengths or very minute differences in resistance caused by the connections on either end is causing the very small differences in potential, and the hum. What do you think?

  • Raymond Garcia

    The hum occers when i plug in my Playstation 3 to my tv

  • Gay James

    Run laptop on battery or use a 3 prong to 2 prong adapter. buzz will likely cease. This is the first thing to try with laptop buzz issues. No, safety is not greatly compromised.

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