So you've got that annoying hum in your sound system. You aren't sure what it is and you may have just accepted that you'll never be rid of it. Don't despair! It's most likely a cabling issue that is allowing noise from the building's AC power lines into your equipment. Called ground loop hum
, it's caused by a difference in electrical potential at grounding points. But what exactly does that mean? When you have more than one piece of equipment in your sound system connected to a common ground through different paths, like different outlets on the same circuit, you can get a ground loop. As current flows through your system, the ground loop creates a circuit for the current to flow from one unit's ground to a second unit and back to the first. This current then creates hum when it flows through the audio signal ground. So, now that you know what creates it, let's talk about how to break that ground loop so you can finally get rid of the hum.
The simple, inexpensive way to fix the ground hum is to plug the piece of equipment into a different outlet that is on a different circuit. Once you can identify which piece of equipment is causing the problem, this is the easiest fix. For example, if your keyboard on stage creates a hum when you plug it in, get an extension cord or move the keyboard so that it is not longer on the same circuit.
If changing the outlet isn't a workable answer, you'll need to add another piece of equipment to your system. You have some basic choices:
Adding a direct box, like the Rapco DB-1
, that has a dedicated ground lift on it to your system will break the ground loop and allow your guitarist or keyboard players to send a clean feed to the console without the hum. Or, you can use a product like the one from Ebtech properly named the Hum Eliminator
, specifically created to break ground loops. Simply insert the Hum Eliminator between the offending pieces of equipment to break the ground loop and get rid of the hum. Both solutions work to correct ground loop antenna problems that are associated with audio signal cables connected to improperly grounded equipment. They isolate the shield of the cable from the equipment ground which helps to reduce or eliminate hum from the AC power used to run the system or other equipment in the building. We would recommend trying a quality direct box first. But if that doesn't work, the Hum Eliminator may do the job.
Breaking the ground loop is the key to removing hum, but we want to warn you against doing this by cutting the ground wire in your equipment. This may seem like an easy and logical fix, but it's dangerous and it is not the correct way to solve the ground loop problem.
Hopefully, you'll be able to solve your hum problems with one of the solutions listed above. If not, or if you want more information, please call our experts at 1-800-462-8664 and we'll be happy to work with you to find a solution that fits your needs.