This might seem like a dumb question, but don't let that fool you. It is a dumb question.
Say I connect my mics to my MixPre-D, and then connect my MixPre-D to my Sony PCM M10 recorder via line-in.
Using the recorder, I can attenuate or boost the signal. Apparently unity gain is at 4 on the PCM M10, so that's what I leave it at.
But . . . what's boosting the signal if I turn up the gain on line-in? If it's not the recorder's on-board preamp doing the work, what is?