If you’ve run sound for very long, then you’ve probably encountered buzz and hum in your sound system.
And chances are you want to get rid of it, fast!
Buzz and Hum are different.
They sound different, and they have different causes.
This means that fixing them may require different solutions.
Buzz is often a higher pitched noise that can even crackle at times. (Imagine the zzzzzzz and crackle in a bad AM radio station.)
Hum tends to sound lower pitched and it will likely have a tone signature that you can actually hum along with. (Imagine a low or mid-frequency mmmmmm.)
Buzz is generally caused by electrical noise or interference that gets into the audio signal.
This interference can come from bad power adapters or circuits (dirty power), lighting dimmers, fluorescent light ballasts, or nearby high voltage electrical systems.
The best way to prevent buzz is to use quality shielded audio cable and then route that cable so that it is several feet away from electrical equipment that can cause noise.
A good rule of thumb to follow is to keep low voltage audio cables 18” to 3’ (0.5-1 meter) from higher voltage cables and equipment.
This distance is especially important when cables are running parallel with each other. Insulated cables can be closer together or even touching if they are crossing at a 90˚ angle.
You may also find that a damaged cable or bad shield is the culprit in allowing buzz to get into the audio system.
It is a good idea to inspect all of your audio cables for proper functionality and make sure the shield is not cut or crushed.
Additionally, you may need to use a quality power conditioner or even separate power circuits to eliminate interference from other electrical systems. (Consult with an experienced electrician if this is the case.)
Hum can be easier to find and faster to fix than buzz.
Hum in your sound system is almost always caused by a ground loop.
There are a lot of complicated ways to describe and diagnose this problem, but the most common instance where hum happens is when two different pieces of equipment are plugged into two separate power outlets and then connected with an audio cable.
There can be a difference in “potential” between the two different power outlet’s ground connections. One outlet's grounding conductor (the third prong on most outlets) may have more or less resistance to “earth ground” than the other.
Don’t worry if that sounds confusing. The important thing to know is that this is an electrical grounding issue and it can be fixed fairly easy.
Fun Fact: The sound of a ground loop changes depending on what country you are in. Hum in North America starts at around 60 Hz and its related harmonics (120 Hz, 240 Hz, 480 Hz, etc.). Hum in Europe starts at 50 Hz and its related harmonics (100 Hz, 200 Hz, 400 Hz, etc.). This is due to the frequency of the electrical grid and power generation system.
To fix hum, you often just need to lift the shield conductor on one end of the audio cable that is affected.
This is super easy to do if you use a direct box (like when a bass guitar plugs in and the instrument level signal is converted to mic level).
Most direct boxes (like the Whirlwind Director pictured below) will have a ground lift switch that allows you to easily lift the shield and eliminate the ground loop.
Another way to get rid of hum is to use something called a 1:1 isolation transformer. This is NOT a signal converter (like a direct box), it simply connects in-line with the signal and allows it to pass through a basic transformer.
The transformer will let the clean audio signal to pass through while it blocks the hum from crossing over to the other side.
I always keep one of these handy units to help troubleshoot and provide a temporary quick fix until a more permanent solution can be found.
Another way you can avoid and fix hum is to use shorter instrument cables and make sure they don’t wrap around or run too close to power cables. The safest maximum distance for unbalanced (2-conductor) instrument cables is about 20’ (6 meters).
OK, you might have guessed this was coming, but I have to say it…
Don’t use a “cheater plug” to lift the grounding conductor of a power cable.
Will it work to stop the hum in your sound system? Yes. (But it depends on what piece of gear you use it with.)
So why shouldn’t you use it?
Lifting the equipment ground from an electrical device creates an unsafe operating condition that could cause big problems in the system if something goes wrong or if an outlet is wired incorrectly.
There have even been singers and guitar players electrically shocked on stage because of bad grounding. It’s not something you want to mess with.
It is best to use the methods we discussed above to isolate the ground/shield on the audio cable.
And if that doesn’t work, use something like the HumX power adapter from Ebtech to stop the noise while maintaining a safe electrical ground connection.
Have I used a cheater plug? Yes.
Do I have one in my “fix it” kit? Yes.
But I ONLY use it for troubleshooting purposes to help identify a piece of equipment that may be causing a problem.
Using a cheater plug can help you isolate a bad power supply or equipment with a bad ground connection. Once you find that piece of gear, you should either remove it from service or try plugging it into a quality power conditioner, separate power circuit, or swap out the power supply if that is an option.
Do not use a cheater plug, even “temporarily”, for active system use. It might work to remove the hum, but it could be at the price of an unsafe and hazardous electrical grounding system.
Whatever you do, don’t let buzzzzzz and hummmmmm ruin your worship service!
Troubleshooting your sound system (especially buzz and hum issues) can feel daunting at first. It always helps to have a good mental map or schematic of your sound system wiring
There are three big tips I can give you for troubleshooting.
#1 Start by eliminating the simple stuff first. Many sound system issues can be caused by bad cables. Don't assume you have a bad component until you've checked all of your cables and connections.
#2 Be methodical when you troubleshoot. Have a strategy. Write it down before you start if that helps. That way you can check things off the list that you tried so that you don't go back and repeat the same test that you tried earlier in the day.
#3 Divide and conquer. For larger systems or more complex problems it is useful to find a middle point in your system so you can identify a problem in one half or the other. This can save a lot of time checking every variable of a complex system. This method works great for digital systems as well.
And don't be afraid to reach out for help or get a second opinion. The Great Church Sound Techs Facebook group is a great place to get ideas for fixing your audio problems.
Once you do find your buzz or hum issue, it might involve a cable repair. Use this free guide to help fix those bad cables or loose connectors.
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