Here's a video I did in my shop to demo the groove tube sockets which are pretty cool. The compressor on the video camera was squashing any ability to really hear the amp. You can hear it ease up at the end. I was showing amplitude of the voltage/power before and after.

These are really cool items to have around when you don't feel like using a distortion pedal. With a set of these you can have the amp produce the distortion, which has it's own unique sound.