I have a Sennheiser mic, and when I plug it into the HMC40, the audio goes mute.

This isn't a XLR adapter mic, any ideas why the audio goes mute? I've tried messing with settings and nothing helps. The mic IS turned on.

I spent a good $250 I'd like to use it :) Thanks in advance.

Ran across this last night on a friends HMC 40 and sennheiser video mic... She had accidentally left the cable from the 40's optional audio unit plugged in which takes priority over the mic input.
That's about the only thing I can think of.

Not sure I get what you mean (sorry for late reply, forum is supposed to send out emails when I get replys). I only have one thing plugged in, and that's the mic. Sorry, just confused. :)

Do you have the optional XLR audio unit attached to the camera?

Hey, no I don't. Can't afford it :)

Hmmm . . . what model of Sennheiser are you using? Is it a condenser that needs a battery?

MK 300 I believe. I'm getting a battery tomorrow if the weather is good. It did work on my VX2000 with no problem so I assume the battery is good.

Battery fixed the issue! Yay :)