I'm having issues with the line in jack on th eback of my dual g5. I've bought three different desktop microphones with miniplugs, and none of them work with the line in port. I'm prettty sure the port works since I can plug my headphones into it and get a signal using the headphones as a mic. But three seperate computer mics have failed. I suppose that there is a chance that I happened to buy three bad micrphones from three different brands from three different stores, but I'm sure the answer is much simpler than that.... any ideas?

OK so I tested the mic with a little audio recorder and the mic works fine. I plugged headphones into the line in port of the computer and got a signal there, the the line in port works fine. The two jsut won't work together. Maybe it has something to do with it being a balanced input - the microphone's mini plug is stereo - maybe the signal is cancelling itself out?....

Sounds potentially defective to me. If it's still under warranty, I would definitely take it into an Apple Store for repairs if I were you. It's always worth taking care of ANY problems that you can before your warranty expires.

except that the port does work - and so does the mic - just not together. I'm going to bring it in for an unrelated problem anyway, maybe i'll bring it up with them then... Personally - I think it may have something to ddo with the fact that it is a mono mic with a stereo plug. On the off chance that the line in input is balanced (though I doubt it) that would account for this particular mic not working. My Sony MS stereo mic works in the port and so do headphones used as a mic. the only difference I can think of between those two and the one I want to use is that it is a mono signal instead of a stereo...