As others have said, tubes and "crystal clear tones" do not generally go hand-in-hand. Solid state circuits are much cleaner (noise and distortion wise) than tube circuits, thus the "need" distort the signal with sims if you want the old tube amp sound. I cut my electronics teeth in high school with tube amps, radios, TVs etc. It's hard to believe now that you could buy replacement tubes in the local convenience stores, since they failed so often. They always seemed to fail when you were watching your favorite TV program. My dad would smack the side of the TV and that sometimes helped jostle the broken filaments back in line, but eventually we would take the tube down to the local 7-Eleven, test it on their machine, and take a new one home. Ahh- those were the days lol. By that time transistors and integrated circuits were pushing tubes out and when we wanted to build a really high gain multi-stage amp (not for musical instruments) we were very happy to have clean solid state.
My son's Zoom H4 mic has a whole bunch of input filters you can choose if you want it to sound like various models of old tube amps. I didn't find any of them pleasing on my uke, except a few of the very mild reverb settings. Which sounds better is a matter of constant debate amongst audiophiles, but for me the uke sounds better clean.
Geeze - I am really getting old!!