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Anyway, have you checked System Preferences > Sound > Output yet and can tell us, what is listed there as Output Device?


 
Please don't take this the wrong way, but a friend of mine had a similar issue as what you're saying, but it was much simpler.

A mac has 2 volume levels, one for something plugged in and another for the internal speakers. Are you sure it's not just set to the default mute for your headphones?

Or does the volume control stop working all together when the headphones are plugged in?
 
the volume on my mac is mess up

it just stop working the volume control i have to go into system prefrance to adjust the volume or restart it so it fixes it:apple:
 
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