Guys, I own a Saffire Pro 24. I use an Beringher MIC200 pre before the mic1 input. Must I set it to "Line" and give more gain to the pre than setting it to "Instrument"?
If you use another mic pre (with HiZ input) before Pro24, you need to feed that into a LINE input. If you're using a DI box, you need to feed it to the microphone input.
If line and Hi-Z does not have difference in gain, mic pre into either inputs can give no difference, so it is safe to plug into Hi-Z in case of absence of normal line input (for such interfaces). Difference becomes obvious for non-line signals.