Audiophiles love their tubes. They think they sound better. I don't believe it, although I can believe that vacuum tube amps sound fine. Lately chinese companies have caught on to the demand and have started selling relatively inexpensive tube amps to the mid- to high-end market. This lead me to wonder whether they are even using the vacuum tubes in the circuit. It woudn't surprise me if they are just biasing the heaters so that they provide the warm tubey glow, while using some mass-market integrated stereo amp inside the case.
Actually that sounded like a great idea. I needed a substantial amp at the time for the big, expensive headphones I had. I got it in my head that I would make a headphone amp, and I would put some random vacuum tubes on the top and bias the heaters so that they glowed, but I wouldn't actually use them in the circuit. I even planned to take them to headphone conventions (yes, they have those) and let people listen and comment on how "warm" the tubes made the sound.
After a bit of googling for vacuum tubes, though, I actually found a hybrid vacuum-tube/transistor amplifier schematic that uses the vacuum tubes for the preamp stage that adjusts the volume, but uses common transistors for the output stage. Another great feature is that it will run on a cheap 48V ethernet power supply. I decided to go ahead and build that since the tubes are still quite available. The amp has a very nice sound and drove the K701 headphones I had very well. I don't think the vacuum tubes make the sound any better, but they do look cool and that's important. I'm really happy that there is absolutely no audible hiss even with the volume turned all the way up. And the volume does go WAY up.