If you really want to go crazy with experimenting with tube tones... get a THD!!! But if you really want to get the most tone out of your tubes it's worth looking at an attentuator. This will allow you to saturate your tubes all the way even when you're playing at level 1. Most people Have tube amps that they never even get to hear the true tone of because they never crank them past 2. To get the tone you have to supply the tubes with all the power. The attentuator allows you to do that without having the volume way up. I know you're wanting to know more about tubes themselves... and this is something you should know.