Consider the fact that you have 3 sets of gain knobs... you don't want to max one, min the other, and end up overloading one of the intermediate stages.
I suggest the following, other opinions welcome:
- setting the M10 to mid-range (5).
- set the L/R gain on the UA-5 so you get the occasional blip on the red light, or just set them to 2 o'clock
- adjust the headphone jack volume control to bring the M10 gain the way you want them.
- there is a little red light on the UA-5, not the phantom power one, the other one... ideally you would turn that off, it's said to reduce the amount of circuitry the signal has to go through.
FYI, I don't know if people realize this but you can do standalone analog out recording with a STOCK UA-5. You need digimod to get digi-out without a computer, but a stock one will put out an analog signal. I've done it.