So you've made the decision to buy an external headphone amplifier for your desktop setup. Awesome. It's an easy way to make your nice pair of wired headphones sound better (because your computer's built-in amp just frankly isn't very good) — and you want that. Now you just need to decide which one to buy.
There are two main types of headphone amplifiers out there. A solid-state amplifier amplifies the electrical signal using transistor circuits, while a vacuum tube amplifier does the same thing with vacuum tubes. The do effectively the same job, just in different ways. The thing is that there are more solid-state headphone amplifiers in the sub-$200 range because they have less moving parts and are cheaper to make.
Tube amps just sound different
A vacuum tube amp can definitely be considered the "elevated option." They're more expensive because they're more complicated to make, but you find still models that are relatively affordable vacuum tube amplifiers, like Schiit Audio's Vali ($149) or Vahalla ($349) . That said, a vacuum tube amplifier isn't definitely make your headphones sound better than if you had a solid-state amplifier — it's just a different sound.
"Some people (including me) think there is something 'better' about the sound of tube amplification," said Jason Stoddard, cofounder of Schiit Audio, a California-based audio company that sells both kinds of amplifiers. "We don't really talk about perceived sound, but many audiophiles have commented on tube sound being somewhat more 'liquid' or 'natural' through the midrange. This is what I perceive as well, though this is not measurable in terms of frequency response."
The other thing with vacuum tube amplifiers is that you can swap out and try them with different tubes, which changes how they sound. It's an allure for tinkers (which audiophiles inherently are), in much the same way how people try out different preamps, photo cartridges, styluses (and more) with their turntable setups to customize the sound.
The design is undeniably cool
So the sound quality is admittedly subjective. The design of the two kinds of amplifiers is also subjective. If you ask me (and I think most people), vacuum tube amplifiers have a "wow" factor that solid-state amplifiers can't compete with. The tubes stick out and glow when you're listening music. It just looks cool — and admittedly a little intimidating.
Vacuum tube amplifiers aren't reserved for audiophiles, but if you're somebody who is thinking about buying one, there are definitely a few words of caution. First, with their exposed glass tubes, they're definitely more fragile. And two, they require more maintenance; the glass tubes of a vacuum tube amplifier will eventually need to be replaced (Stoddard says after about 5,000 hours of run time).
A vacuum tube amps isn't a set-it-and-forget-it option. It requires more maintenance, but it also allows for more customization. But are great-yet-different options. "If you really don't want to deal with things, get solid-state," Stoddard said. "If you like playing and experimenting a bit, go tubes."