I recently did a popular mod to my Superchamp XD. I put a line/poweramp in so that you can just use the tube preamp, without any of the digital or solid state that comes before it. At the same time I also added a poweramp mute switch so I could use the line out and play when son is asleep in the house. The line in mod will also mute the speaker when a cable is plugged in, but I put the switch in as well because its easier than finding a cable and plugging it in.
Tube amps can be dangerous. Always observe tube amp safety: