This amp is a funny thing. It's a solid state amp, not tube - the picture is wrong btw, I couldn't find one of the 20hd. But yet, it behaves more like a tube amp. It gains some headroom as you turn it up, like an old Marshall would. Is it the greatest simulation of a tube amp ever? No, the BIAS or Kemper or something like that would do that a lot better, but for the price, these things are rippers!