I have the new 60d as well. I’ve tried playing around with different microphones and inputs. The built in microphone doesn’t have any hiss but the quality is unusable. I’ve tried two different microphones two completely different plugs with the camera’s mic input and as soon as I plug in either mic I hear the exact same hiss. It’s obviously due to the 60d and not the microphones. And the only thing the audio level control does is reduce the total volume of the hiss.
I don’t know how to fix it.