^^^ No. But if, using whatever input you are using, you find that your levels are almost clipping (i.e., hitting zero) even when the REC knob is almost all the way down, you are running too hot and should use a lower sensitivity input.
There are some decibel meters you can buy for devices like the iPhone. They're fun to play with, but I don't know how accurate they are.
Good general rule which is true of almost every small recorder:
1. Start with line-in. If you get a good signal, use that.
2. If you don't, go to MIC/LOW SENS
3. If you still don't, go to MIC/HIGH SENS
In other words, there is never any harm starting with line-in. Once you do this a couple times, you'll find out what generally works for the shows you go to. I pretty much don't have to even mess with REC level knobs or that stuff during shows I go to, because (a) with digital, it's so much easier to fix things in post and (b) I know what the settings are likely to be before I go. Practice makes perfect.