60D Audio Gain in Video

[rexbobcat]

I just took some video for a friend of mine who is in theatre and needed me to video her monologue. We were on a large theatre stage and it was very quiet except for her speaking. When I listened to the audio there was a lot of hissing, and it sounded like there was a fan blowing. But there wasn't. I was using manual audio levels.

I'm just curious if anyone has any experience with audio gain on the Canon EOS 60D? Unlike the T2i and the 7D, the 60D has manual levels. However, what I've found is that this really only affects the overall volume, and the hissing noise is still their as if AGC was still in use. And if I do record at a lower decibel, and then try and bring it up in Adobe Premiere, the hissing is even worse.

I can kind of cancel out noise in Adobe Soundbooth, but it causes a lot of distortion at certain volumes or frequencies. Also; I'm using the onboard microphone. I assume that probably makes a difference? If I get an external mic will I have problem with the hissing?

Everybody was praising the manual levels on the Canon 60D, but I haven't found it to be any different. From what I can tell, it just affects volume.