Okay, so I bought these things: Shure SM57, Behringer MIC100 tube ultragain, ESI UGM96.
The problem is, the recorded sound does not reach reaper. The preamp (behringer) seems to be getting the signal, but still no sound. I already changed my system preferences. Line-in: ESI UGM96 and Line-out: ESI UGM96. I also changed reaper settings too. When I changed my system preferences, I noticed that the signal was reaching my mac through the mic, but I didn't hear anything, and when I record, no sound. I tried using audacity too, and I could get some sound if I changed it to 2 (Stereo) Input channels.
If I do this, I only get sound from the right side. What am I doing wrong?
The problem, if the sound is reaching through the microphone, is that you're using your microphone as input device.

You don't need to change the system setting, too, for Reaper's are separated from them.

Open reaper, go to the preferences (reaper's, not system's), select the UGM96 as input device and, if you want to, as output device too.
Then create a mono audio track and select "input 1" as input for that track.
Plug your preamp into the first (usually the left one) input and play!

Be sure to have your input monitoring active for that specific track, or you'll not hear what you're playing, though reaper will get that.
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