Equipment Question

[ddouglass]

Has anyone ever used any type of feedback destroyer/active filter to stop microphone feedback? Pros and Cons?

I have a couple of singers who have high pitched voices and sing too soft. This requires a very delicate balancing act between getting the microphone sensitivity up high enough to hear them without triggering feedback if they move within 20 ft of a speaker. I need someway to squelch out the feedback without having to constantly adjust the mixer controls.