This is a bit of a misconception for a lot of folks. When you're recording you are always using a preamp. All mixers, DAW, recording interfaces, etc. with analog inputs have preamps of some kind built in. The vast majority of microphones out there use a ballanced, low impedence signal. This has to be converted to a single line level signal before recording and the preamp does this. If the device is designed properly and is of good quality, this will happen as transparently as possible. This is great for signal integrity, but not always best for "tone". Many folks like the "sound" of some preamps over others for various reasons. Many like the warmth and smooth compression offered by tube based preamps, while others like the clarity and high headroom of analog preamps. It's all about personal preference and how much money you are willing to part with. Dedicated mic preamps can sometimes work wonders in certain situations, but they are not always needed. Placing a $5000 tube preamp between a cheap, crappy mic and a noisy four track tape recorder while in a terrible sounding room isn't going to do much for your end result.