How to Eliminate Feedback on a PA System. We've all heard that terrible squawk from a microphone's feedback. The speaker places his hand over the mic, trying to squelch the problem, and it gets worse while the poor crowd winces at the grating noise coming from the speakers. Eliminate the feedback on the PA system before the crowd gets there.
Set up your main speakers so that they are in front of, and well to the side of any microphones. Keep the master volume all the way down. Place your stage monitor speakers so they are facing the musicians. Connect the microphones to be used and place on the mic stands.
Set all the equalization controls to flat or right in the middle. This includes any graphic equalizers that may be built into your PA mixer, or external models. The EQ sliders should be set in the middle not pushed all the way down.
Ensure all microphones have been muted, turn on monitor amps and increase amp volume to full. On the mixer, turn the master monitor volume (sometimes known as aux 1 or send 1) to "U" which is unity gain.
Turn down all the individual channel monitor volume controls then un-mute the lead vocal mic only. Advance the sliding volume fader to unity gain and then begin testing or checking the mic as you slowly increase that mic's individual monitor volume control. As you continue to increase the volume, you will begin to hear the system becoming unstable as feedback just begins to be noticeable.
Cut or lower the frequency control that will stop the feedback. This could be treble, mid, or bass. Instead of turning the individual tone controls, slide the frequency control down enough that it will eliminate the offending feedback. Continue to raise the channel monitor level to see if there is another feedback that will be created. Just as before, when you hear the feedback, find which graphic slider will stop it by lowering it on the graphic EQ.
Turn up the other mic channels, ensuring that the monitor levels are less than the lead vocal. Lower the channel monitor levels by approximately 10 percent to give plenty of room before the feedback range begins. You have now "rung out" your monitors to prevent feedback during the performance.