We all know that using a cheater plug to lift a ground is a bad idea and can kill someone. But what's a SAFE way to lift a ground?
At the outlet:
1. EbTech HumX
Cost: $60-75
Details: Good for up to 6 amps of current. I keep one of these in my gig bag. You never know when you'll need to SAFELY fix a ground loop problem with a laptop or other device.
At the signal chain (RCA) based:
1. Radio Shack Ground Loop Isolator
Cost: $20
Details: Model # 270-054. Designed for car audio, this product works supremely well at removing ground loops caused from video distribution networks in bars - a problem common to karaoke rigs. I've kept 3-4 of these in my troubleshooting bag and swear by them. I put them on all my karaoke players. Yes, I've been using these to fix ground loops for roughly a decade.
2. RDL (Radio Design Labs) AV-HK1
Cost: $115
This is a professional product that has both RCA and miniplug connections. If you have a ground loop on an ipad or something similar then this should be able to help you remove it.
Cost: $45
This is another professional level product that has both RCA and 1/4" connections and has the added bonus of converting unbalanced to balanced or vice versa.
At the signal chain (TRS/XLR):
Cost: Depends on model
Details: This unit comes in a couple different models - a pair of two channel devices designed for use with either TRS or XLR connections and two 8 channel rack mount models offering TRS or XLR connections.
As you can imagine, I'm a big fan of EbTech's products. Why? They WORK.
Troubleshooting a ground loop...
1. Start at the amp/powered speakers. Remove the input into the amp and see if you still have a hum. If you do you have a serious problem with the gains or something else.
2. Plug into the mixer - but do NOT have anything else plugged in. If you experience a ground loop between these two devices and you're using balanced XLR or 1/4" connections - the TRS/XLR EbTech Hum Eliminator should fix the problem. Alternatively, if the power draw isn't that great (sub 6 amps) then the HumX is another option.
3. Add each device individually and see if the ground loop appears. Depending on the connection type, either a HumX, Hum Eliminator, or the Radio Shack Ground Loop Isolator should resolve it at that point.
4. If the problem is intermittent, see if you can find the source. In some cases, it's RF or motor noise from a refrigerant compressor, blender, or something similar. Power cables with an RF choke may help to resolve the issue, as would a power distribution unit (PDU) with RF and other noise protections.
5. If the problem still exists, we recommend talking with someone who's trained as an electrician or electrical engineer to discuss your specific issue. In some cases, the building maintenance people may be able to provide additional information about the grounds and outlets that are less prone to noise and other issues.
If you experience RF based noise one possible solution is RDL's RF Noise Suppressor. The problem is that the wiring of this device requires knowledge of the problem and what you're trying to accomplish because the wiring is adapted to solve the specific issue.
I'll be adding other methods to lift the ground SAFELY in the future as well as other helpful hints. If you have a favorite ground lift product feel free to share and we'll add it to the list. If a manufacturer wants to send us a product for review or testing - we'll be happy to run it through it's paces.