What kind of mic? And are you talking about going into a computer or is this just a general mic question? Of course if you are going into a computer you want to check your line levels in Windows (or Mac if thats what you're on).
Also does this mic require phantom power or some kind of pre-amp? Some mic's have batteries inside to act as the pre-amp, maybe your batteries are low.
It could be a couple of different things, but more info is needed.
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