Can I plug my Mic into the Mic Jack on my Mac?
A. Your Mac doesn’t have a Mic jack, it has a Line-In jack. Line Level is “louder” then Mic Level, so your Mac is expecting a louder signal, thus you’re not going to get very good results plugging a mic in, it will be too quiet. Additionally, if you are using a Professional mic (like a Shure SM57, etc.) with an adaptor plug, you have an impedance mismatch (The mic is Low Impedance and the Line-In jack is High Impedance). When a signal hit’s a mismatch it’s like hitting a brick wall, most of the signal is reflected back and does not get through. There are a variety of USB and FireWire interfaces that will allow you to plug any kind of mic into any current Mac. Another choice is to use a Mixing Console. Plug your Mic into that, and the Console into the Line-In on the Mac. Small Mixers can be had for very little money.
