My client is speaking into a microphone then going directly into the camera. Does anyone here recommend some sort of preamp or anything that can help warm up the vocals and perhaps even have a compressor?
You can do that somewhat in editing. As far as doing it "live" you didn't say what type of microphone you/he is using. What type of connector does it have?
Is this a fixed shoot (at a desk or chair) or is the subject moving around?
My take on it is that as long as you're getting a clean undistorted signal, leave anything else for post. You can't easily remove anything you add while recording, so if you decide you don't like whatever it is later you're stuck.
A videographer friend of mine swears by Sound Devices MixPre. It's a 2-channel Compact Field Mixer with Input Overload Protection. sweetwater.com/store/detail/MixPre/] . It's over $600 - but places "unclippable" input peak limiters in the signal path - and he thinks it's worth the cost. Battery and AC operated.
Who makes the SD-522 ? I have been thinking about a field mixer and I liked the idea of the limiters built into the Mix Pre - but it seems pricey to me.