I posted this on the audio forum and only got 1 reply, so thought it may be more product specific to post here. Can anyone tell me the right way to calibrate audio using a GL2 and a Sound Devices MixPre? I have AT 8202 pads which will reduce the input in settings from -10. -20 & - 30 db. and a cable made by Front End Audio for me to take it into the camera.

What is the correct setup and procedure? Thanks much!

These are general observations. I have not used the MixPre you have.

For best S/N ratio in the GL2, use the MIC ATT or line level setting for recording audio.
However, that assumes your mixer output a nice, quiet signal that can drive the GL2 audio input.

For highest quality sound use manual level control if you have the ability to ride the levels as you shoot. While the automatic audio level control is not bad for what it is, it still can convolute the dynamic range of the audio - if that is important to what you are shooting.

Use what ever pad (10,20, 30 dB) you need to match the MixPre output to the audio input level on the GL2 and maintain the head room you need to avoid clipping on peaks.