Fixing Portable Audio Problems (Hum, Pop and SquEEE!)
Public Domain by John Pilge
SOME WORDS ON POWER AND SAFETY
You need a six plug power strip with a built-in circuit breaker. I don't mean an on/off switch -- which is handy -- but a power strip that has a fuse in it that you can replace. These cost between $12 to $25. Ideally you only need six outlets. If you add two of these handy strips onto the same source, you can create a fire or cause the main circuit breaker to trip and the room has no power.
If the power goes out, the staff get cranky, the manager starts yelling, and the audience tries to steal your equipment.
If you can keep everything to one six plug power strip, you can explain it isn't your fault. Maybe someone started the dishwasher and it is on the same circuit.
Having a power strip with a circuit breaker also makes mister I-got-my-own-microphone-so-I-am-special announcer happy. It is a good investment. About $2 worth of fuses versus $3,000 in equipment.
You are all set, power on and there is a low hum. This is the sound of a grounding problem. Likely cause is a two-prong outlet. Typically you use a three-prong to two-prong adapter. You have to attach the extra lead of the adapter to the screw in the center of the wall plate. If the building follows standard code, that acts as a ground. Still got a hum? Easiest thing to check is if the wiring has a proper ground. I use a three-prong circuit tester. I plug it into the power strip and it checks for bad ground, open ground, open neutral, hot ground, hot neutral and hot/neutral reverse. Sure it sounds complicated. It is not. If there are two lights (and none are red), everything is fine. Tripp-Lite makes and sells a three prong circuit tester. You can use a fancy circuit tester. But don't let the manager see you pushing the leads into the power sockets.
If you have an open ground, and the plug is secure and correctly installed then there is no easy fix. Warn the manager before you start. Maybe you can find another outlet.
The circuit is fine and you STILL have a hum? Bad news, now it gets complicated. Power on one device at a time and listen for a hum. If it is one device, check the cords by lifting a section and bend the cord. If the hum stops at some point, you have a cord with a broken connection. (That is why we tell singers to NEVER swing the microphone by the cord.)
Is the hum on more than one device? Sadly, this typically means they are sharing a ground. You can separate the power sources if that is possible. Otherwise, tell people to talk loudly into the microphones. You are now working with a hum.
POP (Did you hear a pop? I didn't.)
When a singer puffs at the microphone it makes a slight pop sound. The audience hears it, you hear it, but few on-stage can hear it. Put a wind screen over the microphone. It is called a microphone wind screen. If you call at Radio Shack and ask for a microphone sock they may think you are asking for a quarter-inch jack adapter. The microphone wind screen is required for all outdoor gigs. The slightest breeze will cause a noise in the microphone. If you ever get a copy of the San Francisco Symphony first (recorded) outdoor concert you will hear thunder. That is from the wind hitting the microphones, not the weather.
TWEEEEEEEEEEEEEEEEEEEEEEEEEEEE! (Ow! stop that!)
Point the speakers away from the microphone. Sometimes you can put the speakers in front of the stage. There is one other solution which no one wants to consider. Turn the speaker volume down.
One other tip. My most often used tool for setting up is a flashlight. On the way to the site, look for a convenience store and check if they have the proper batteries you might need. Don't forget the wireless microphone and the 9 volt battery.
About the Author:
John Pilge is a photographer in Northern California. I worked in radio also.