Wow, I got a response! Thanks so much. I am still learning what all the terms and concepts mean. I do not want 40x gain but want line level signal (if those are different). I think I am looking for about 20x gain maximum? I could put in a potentiometer I guess? (Or, maybe not).
I hope my questions/suggestions are not too odd. I truly am trying to educate myself on this. As to simpler routes you mention, I would be very grateful if you could elaborate. First, let me say what I am trying to do.
I am using a Linux-based netbook when I travel, which is a lot. I have modded it to run quite well as a mini-DAW. I use it to just capture ideas but have been frustrated with just using PIP from its onboard preamp. I have made a simple stereo microphone with a set of Primo EM172s. They require a minimum of about 3.35v to operate well and they get it from the PIP of the netbook.. They sound good but there is a constant "hiss" which I believe is the crappy preamp on the netbook. So, I am trying to go around it with a line level signal. The input is both mic/line so I am assuming there is some sort of switch in the input that senses the input level and adjusts accordingly.
I made battery powered preamp that is better but has little "musicality" to it? It just seemed to me that it would be cool if I could use the 5v power provided by the USB to power the mics and preamp. One challenge I have not wrapped my newbie brain around is how to ground it. I am assuming that the ground going back to the USB power port might work? That might mean though it conflicts with the ground going into the line in jack.
Anyway, that what prompted my question above.
I am happy to answer any questions and really appreciate the response.