Just bought a new canon c200. I started testing with brand new mics (Sennheiser g4 lav & MKE 600) and noticed a distinct & persistent white noise "hiss" sound in my noise floor. This is heard both when monitoring audio in camera and on my computer in post.
I've tried everything to mitigate the hiss: adjusted mic AF out/Sensitivity, swapped XLR cables, tried different mics (Rhode NTG-2) but I still get the hiss. Then I realized I can still hear the hiss when no mics are plugged in. This led me to believe it is coming form the camera's internal preamp. The hiss becomes noticeable once I adjust the gain beyond 5 on the camera for both audio inputs.
I did similar tests on a colleagues c300 and encountered the same issue: I could hear a hiss after increasing the gain beyond 5. I've called Canon Support and they suggested signal interference but I did more tests (stood out in a field with everything unplugged and still got the hiss) and if that doesn't work I should send it in for service.
Does canon just have crappy internal preamps? Can anything be done? Should I buy an external preamp to get clean audio?
Here's a example of the issue (recorded in a closet without any audio inputs) as the gain is increased from 0-10: https://vimeo.com/791269300