Thanks for that, that's good info...
Now, what kind of started some of this was my use of my mic's -10db pad in order to avoid using my R4's -20db pad. The trade-off sounds like it's an "add more noise by using the mic's pad and less noise from the R4's preamps b/c you don't have to use as much gain" vs. the "don't add noise by using the mic's pad but b/c the R4's pad is bigger at -20db you add more noise by having to using more gain on the R4 preamps." I'm also a little curious about whether using a larger pad (in general and all other things being equal) is worse than using a smaller pad.
But beyond that, and upon reflecting more on DSatz's comments, it seems like I might want to reconsider using the R4's pad a little more often.
One other question I have -- given what DSatz just said -- is that as an owner/user of AKG480's, I actually have a +6db setting on the same switch as the -10db pad (it's +6, 0, -10). I wonder if by using that, I can actually raise my signal higher off the noise floor, which would be great. If that's true, then it'd be worth doing as long as the signal doesn't overload the mic's built-in preamp in the body. Considering I record a lot of acoustic jazz, classical, and chamber music, I might be better off going +6 on the mic, and then go line-in (pad on) on the R4 if it's too loud for mic in. That'd get my signal higher off the noise floor by using the +6, then the pad on the R4 would keep me from clipping the recorder, and because of the +6 on the mics, I'd need less gain on the R4. This might be moot though, because I can usually run mic-in for a lot of my gigs (at 0 on the mics).
Interesting...