Microphones

If no sound is coming in and you have plugged your 3.5mm jack into the line input, it is more than likely not the fault of the microphone. The line in is not amplified, so a pre amp is needed. If you run it through a powered microphone, like one from a lecture or whatever that should be enough, or an external USB sound card is commonly used here. Otherwise you can purchase a USB connected mic; or use line out from one computer into the line in on the Mac or any device really with an amp in it. Basically it is because on a normal sound card you have mic, line in and line out but on a Mac you just have line in and line out, line out is amped and line in expects pre amped input.