I use a HM700 and never had any problems with until now. I have a shoot coming up in a studio environment, several pieces to camera in front of a green screen. I’ve been doing some mic tests to find which mic I’ll use (ECM77 or Tram50, both wired) and to get some idea of levels.

I’m getting slight ‘background noise’ when the talent is not talking, as if the mic preamps are faulty, phantom is on and levels on the camera are around 5 to 6 on manual, turning phantom off on the camera and using batteries in either of the mics makes no difference. The best result I can get is to feed a mic into a battery powered mixer, use a line out and line in on the camera and the noise disappears.

The noise can be filtered in FCP (or FCPX) but I’d like to know if anyone else is getting this with a 700 in a quiet environment with a quiet speaker or should I get the camera looked at.

Dumb question - have you tried changing out the XLR audio cable?

It sounds to me like you are occasionally dropping phantom power. It's either the camera or perhaps the cable that the audio (AND the phantom power) are passing over.

Shaun, no question is dumb when you don't have an answer!
However, yes, tried about 10 different XLR's, same result. I can get less noise when the camera audio gains are set to around 2 and feeding the mic through a mixer and using the mixer gain to get an acceptable record level - just seems to me to be noisy preamps in the camera.

It sounds about right. My 700 does have some noise in the pre-amps. I wish it didn't but...
I have a pre-set in my NLE (Vegas 12) and I have presets in my various audio programs just in case but honestly I have only ever used the one in Vegas. It's not a big chunk but you can hear it and it does bother me although one time I forgot to clean the audio (some run and gun stand up interviews at a trade show) and the client never noticed anything wrong. So it's not too bad but...

Thanks Don, I've not really noticed it before but the test for this shoot showed it up, sounds a bit like room tone but it shouldn't be there in this studio setup. I can work around it, the background noise removal tool in FCPX at 5% to 7% sorts it but wondered if it might be something that could be fixed by a service tech.

I forgot to add to my earlier post that I don't know if that's the way they all sound or if the preamps on mine are just noisey, but again the little noise that is there is quite easy to clean out.