I catch bits and pieces here about how great tube amps are supposed to be. I'd like some links to sites with basic information about tube amps and how they work. One thing that usually leaves me scratching my head is how they can use so little power. I've run across a few on Ebay and Audiogon that boast numbers of watts down into the single digits and low doubles. I'm curious why I need a receiver with 100 watts of power per channel when these little things (That frankly look like a bunch of junk attached to a base ) need only a few. I'm familiar with the concept of headroom, but how do tubes compensate? Some other questions I have: What exactly are the tubes? What's inside of them? Do you still use a normal pre-amp with tubes?