I currently own a Sound Devices 702 recorder, and I'm quite happy with it, but I'm stuck with a doubt that has been going on my mind for a while, and it concerns on the use of a mixer/pre amp.
Whenever I've used my 702 (which I've done a lot) I've always been happy with the results, but I've never been sure if a better sound quality could be achieved adding a good pre amp, say a Sound Devices 302 field mixer, to the equation. And I'm asking this only in terms of better sound quality, because I know already that a 302, for instance, allows me to have more channels than the 702 has.
How much better can a sound recording get with a field mixer added to a Sound Devices recorder?
Aside from having more inputs to feed the 702 and a selectable HP filter on the 302 it's highly unlikely you'll gain any sonic benefit overall. SD's preamps are some of the best around. In your case, less is more.
Eric is correct. Sound quality wise your 702 is great.
There may be operational differences that may make a difference….
8 reasons for a mixer in front of a camera.
1. They let you vary volumes without shaking the camera or getting in the way of the camera op.
2. You may need to do that a lot with some people. I ride gain even if one person is talking if their voice fades on the end of each line. You can only do this in a relatively quiet environment, otherwise you bring up the ambient noise.
3. Mixer preamps (good ones) sound better than camera preamps.
4. Good mixers have input transformers that scrape off RF before it get into your audio.
5. Good mixers have limiters that allow you to record hotter, keeping your audio further above the noise floor without distorting.
6. Good mixers have EQ that lets you roll of LF HVAC noise before it gets into your audio.
7. Good mixers have mulitple outputs so you can feed more than one camera, or separate recorder simultaneously.
8. Good mixers make your sound better. If they didn't pros wouldn't waste money on them.
You can use Y-connectors for dynamic mics, but you have no ability to change the volume level individually.