Ground Loop Hum: Identifying & Solving it


Every audio system can experience ground loop hum. After you've heard it once, you'll recognize it anywhere - that nice 60Hz buzz! Usually it is a low level hum, but always loud enough to drive everyone crazy!

I have noise in my system, but I cannot tell if it is a ground loop hum? What are some good indicators it is a ground loop hum?

  • In a multi-channel system, or stereo system, a ground loop hum will be on all channels. 
  • The hum emanates from your speakers, not from the chassis of your AVR or power amp. 
  • It will not be effected by your volume control; for example, if you turn the volume up and down, the level of 60Hz buzz present in the system will not change.
  • The frequency, or pitch, of the buzz will not change or fluctuate.  
  • The hum will be constant. It will not be intermittent and be present one moment and not another. 

I never had hum in my system when I had an AVR (Audio-Video Receiver), but now that I have separates (pre-amp & power amp) I do! Why?

 This is because the pre-amp and power amp that is built into an AVR share the exact same ground and therefore ground potential. Since the difference in ground potential is what actually causes your audible buzz, you are less likely to experience this with an AVR.

A separate pre-amp and power amp combination is much more likely to result in ground loop hum. This can happen when the pre-amp and power amp are powered off of different circuits in your service panel (for example, one powered off your circuit labeled living room, and one powered off a dedicated home theater circuit). The same can actually happen by having on device on a power strip and one not. Again, this all relates to the fact that your pre-amp and power amp's potential to ground is different.

Solving Ground Loop Hum: Identifying the Cause
First, you need to identify what is causing your ground loop hum. Please note, when plugging or unplugging connections your gear needs to be OFF!

1. Remove all inputs from your power amplifier or AVR (if using an AVR, you also need to remove the HDMI output to your TV). Leave your speakers and speaker wire connected. Turn the power amp or AVR back on. If the hum occurs with no inputs connected, your problem is NOT a ground loop hum.

 2. Add each upstream device one a time. If you have a power amp, this means connecting your pre-amp only! If you have an AVR, move right to connecting your source devices followed by the output to your TV.

After adding each device, turn the system back on. Does the hum occur? Once it does, you've found the cause. 


Getting Rid of your Ground Loop Hum

If the hum was caused by:
connecting the pre-amp to the power amp 
connecting most audio source devices (CD player, Network Storage Device, etc.) to your pre-amp or AVR. 

 You will need to run a ground strap between the two chassis of the offending devices. The easiest way to do this is to use some spare speaker wire as a ground strap ( at least 14 AWG). Trim the ends off the speaker wire. Then, back a chassis screw off of each device; wrap one end of the speaker wire around each chassis screw and tighten it back down to their respective chassis.

Note: if optical SPDIF has the capability of reproducing your source devices content (# of channels, sample rate, and bit depth), you may wish to consider using it to connect your devices; this is because optical fiber cables are electrically isolating.

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If the hum was caused by:
hooking up your cable box

You have one more testing step to do. Unplug the coax line that comes into your cable box. This is the most common cause of ground loop hum caused by cable boxes. This is because the cable company usually grounds somewhere different from your home's ground and it results in a ground differential. If unplugging the coax feed to your cable box causes the ground loop hum to disappear, you need a cable TV ground loop isolator, such as this one:

Viewsonics VSIS EU

If unplugging the coax feed does not solve the problem, follow the aforementioned ground strap procedure.

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If the hum was caused by:
hooking up your display device (TV, Projector)
hooking up your HTPC

 I never recommend 3 to 2 prong ground lifting adapters. If something happens, the product could not only be damaged, but the chassis could become live and someone could be potential hurt.

I do however recommend the Ebtech Hum X for devices that draw less than 6A of current:

Ebtech Hum X

Your TV, laptop, or HTPC power supply will plug into the Hum X.