Canon 550D Magic Lantern Audio Setup
Camera details: Canon 550D Magic Lantern Audio v2.3 - 23-Nov-2013 version
This is a tutorial for being able to send the correct level of audio to the Canon 550D Magic Lantern Audio input via a 3.5mm Jack. There is of course a video at the bottom of this post with my demo but this is all the steps laid out in text form for easier viewing and understanding.
I begin the Canon 550D Magic Lantern Audio setup but setting my Sound Devices 664 to -10 on the output options. This is basically half of line level which is -20 effectively. I found this out by trail and error. Mic level was too high (even on the lowest setting) and Line level was too low (even on the highest setting)
I am using Sennheiser G3s as a wireless camera link. Normally on DSLR shoots there is more hand-held rigs or multiple DSLRs and so having some linked for post is a feature many corporate and short films like for the editing stage. This also makes software like PluralEyes 100% accurate.
To get to the Canon 550D Magic Lantern Audio menu, you just press the delete (trash can) button to access the menu. The audio menu is the first one to come up and as you will see in the video you then just need to adjust the gain to 10dB and the audio being sent out at -10 from your mixer will work just fine.
It flutters on the display around -20 and -21 and also is converting or fake monitoring a stereo signal from a mono source. These settings are as close as you will get for a lineup tone to properly calibrate the mixer to the camera.