What's the difference between a "pre-amp" and a "power amp"?

Answer 1

I'm assuming you're talking about either a guitar amp or a bass amp. Well, a guitar amp has two parts to it, preamp, and poweramp. The preamp is the portion of the amp that shapes the sound of your instrument. You can dial in gain, EQ, reverb, delay, and whatever else effects you may have. After preamp has shaped the sound of your tone, the power amp takes over, and amplifies it with minimal coloring. Thus, poweramp basically controls the loudness of your gear whereas the preamp shapes what type of sound you'll get. Often expensive, they are sold separately if you so desire. Mesa Boogie's Triaxis, and ADA's MP-1 are a very well known and used premps.