Fran is right--Omni is the problem. The next time you buy a mic, look carefully at the pattern sheet and the frequency response. Stick with cardiod, hyper-cardiod or super-cardiod and the feedback problem will go away. And, at least to my ears, the sound quality is far superior.
------------------ Travlin' Easy
PSR-S950, TC Helicon Harmony-M, Digitech VR, Samson Q7, Sennheiser E855, Custom Console, and lots of other silly stuff!