I bought a Shure lavalier wireless mic but can't get it working with my Mac--or a friends Mac for that matter. The problem is I can't get an adequate input line level. I've tried using an iMic into the USB port and I've tried plugging into the input jack directly--no success. I bought a M-Audio Mobilepre USB preamp--no help. I then got an M-Audio DMP3 mic preamp which has more power (67dB of gain). When I hook up a Shure SM57 it works fine. The problem isn't lack of phantom power--the wireless system supplies it. Any suggestions?