One of if not, the most popularized attenuators out there to date. Plug it in properly and you'll be able to crank the snot out of your tube amp and control the overall volume level with the hotplate. This enables you to of course get that great tube saturation at bedroom levels. It's a very simple to use device and doesn't require much, it's really only got one knob and one or two additional switches.
Tonally it is supposed to replicate what a cranked amp would sound like, though in my opinion it replicates more of what a cranked marshall would sound like. This being said, THDs seem to sound great with marshall amps for some reason but everytime I try it with another amp it just doesn’t sound like how I’m used to that amp sounding when cranked. I can’t say why or how but it the THD just seems to give off a more vintage tubey tone all together. I think this is the reason for other revisions of this hotplate being produced by other companies and such. Also feature-wise other companies have upgraded it, some all in one type that allow you to hook it up to any OHM configured amp/head/combo rig.
Though overall, it’s a good product. If you’re a one-amp type of user and just want to get a good bedroom level tone this would be worth looking into. Yes it’s a bit pricey, but compared to when it first came out it’s gotten cheaper. Though personally, I find no use for it these days. As these days most modern amps have decent and usable tones at low volumes. However if you’re got a vintage amp that you haven’t been able to crank and rock out with since your last gig in the 70s in Madison square garden, this is what you want!