Have a 414 myself, and have some "problems" too. Your question, you can take the out of the 12 track and plug it into the sub in on the 414. You control the level with the master fader. This is for using it live. For recording, you'll have to take the out of the 12 track and plug it in to one of the tracks on the 414. Like sub-mixing, you'll have to get all the levels and sound the way you want on the 12 track and then record on a 414 track. Once you do this, you can't go back. It's a one time shot. So practice a few times to get it right, watch your levels. Shouldn't peak no more than +2 on the 414. The meters on this unit are as fast, so some of the peaks on say a kick track might peg the board at +6 and above, you will get CLICKS. Trust me on this, been there done that. With analog, you can record "a little hot," but not too much. You may need some adapters, go to Radio Shack, they got it all. One word on using XLR's on the 414: You can't generally just plug a mic with an XLR cable into a 1/4" jack on a 4-track or mixer, even with a properly wired adapter. That's because the mic will almost certainly have a lower impedance than the input of what you're plugging it into, and that means that unless you correct things with an impedance matching transformer, it will sound like junk. Fortunately these things are available for less than $15 at Radio Shack (you want #274-016), and adapt the XLR plug to 1/4" at the same time.