Noone likes the occurance of feedback. It hurts, it distracts... nobody wants it. Even a small amount of feedback can get you fired from your sound engineering job. How to prevent it then? Let's use a FEEDBACK DESTROYER and ring the system out! Just kidding. I don't believe they really work the way thay were intended to. Instead I would suggest to be mindfull of your signal flow and use EQ wisely. I use my EQs in 3 different ways: - for microphone compenstaion - for speaker compensation - for sound source correction/creative EQ All of these can be combined into one EQ processor, however four parametric bands are usually not enough. What I like to do is to use a channel EQ for sound source color correction, ą group EQ for microphone type correction ("headsets", "handhelds" etc.) and a bus/matrix EQ for lodspeaker correction. I also use the least or an inserted PEQ for correction of acoustic rezonances.