tedandjess, I haven’t looked at my 414 in a while, but I’m remembering a slider for Trim which controls the input level. Effectively it is kind of a fader for the “mic preamp” that Tascam builds into the thing. Do you have this and how are you setting it? It sounds like you don’t have it, but instead a simple switch for either mic or line.
Also, I recall that the 414 does not have XLR inputs, but rather ¼” jacks. If this is the case with yours, how are you getting your mic plugged in? If you have access to any other mic pre, even those on a cheapo mixer, run your mic into it and take a direct out from that channel into the input of the 414. Leave the 414 fader about ¾ of the way up, and set a strong signal from the mic pre.
What is gain staging? There are people on this board who could fill a book on the subject. Although I’m not one of them, I’ll offer this thumbnail sketch. Gain staging is setting optimal level at each link in the signal chain such that a comparable optimal level is passed on to the subsequent link in the chain, and ultimately the recording medium. Optimal level is that which is sufficiently above the noise floor to be heard clearly over it, yet where the peaks are not clipped (or in the case of analog, beyond desirable tape saturation). Noise floor is….oh, screw it!
-kent