WOW! 6XX Owners, look no further.
I have a Dragonfly Red—and it's very good for a small, portable DAC/AMP—but it's nothing like this. Right out of the box with the included tube, BRAND NEW, it sounds more open and more full to me than the Dragonfly. And it looks lovely to boot.
What a joy. Clear, rich, and deep. It's all you need, if not all you could want. And the price is bonkers (especially with their discount).
Six months and hundreds of hours in, this is easily one of my favorite-ever gadgets. Sounds as great as ever and has all of the power I need—but I’ve noticed they can make noise in some lower-quality, lower impedance headphones.
None in my 6XXs (dream pairing!) or my Beyerdynamic DT770s (250ohm).
The 6XXs, as has been mentioned, shine like crazy in this arrangement. They are just plain fun to listen to. Sounds FEEL good through them. It's difficult to describe—but great music really hits you everywhere it's supposed to.
The DT1770s sound excellent too, but not as enveloping for music because they are closed back. They are isolating—not actively and not a ton—but enough—so the advantage is that they envelop you more for games and movies. They block out more and leak less, so it's also better in a work environment or with family around.
But in your own room in a quiet-ish environment (it won't block noise, but with this amp, it's no problem overwhelming it), the 6XXs are amazing.
And as noted in my reviews of the DT1770s, even at 250Ω, they require more power to drive at the same volume as the 6XXs at 300Ω. Not much, but noticeable.
Still, you can cause yourself plenty of damage with either if you want to—and, even if you don't—the details you can reach when you really drive these things is truly impressive. Clear, crisp, WARM, and distortion free. The tube alteration isn't substantial—and I wouldn't want it to be—but it is, in a word, soothing. Nothing is harsh at any level. There isn't any distortion at all in either of the above headphones. Or anything else for that matter.
And another reviewer mentioned a clunk when you turn it on and off? Not at all on mine. Neither of my headphones make a sound when the AMP activates. I can only hear it on the amp itself—when the tube warms (it takes about 30 seconds), the light switches from red to white—the amp makes a tiny (and pleasant) click.
Other than that the only unwanted noise you'll get is from overdriving lower-impedance phones. I have a pair of Vic Firth's—and they are a severe no–go. They buzz like they have a problem, even at a low volume—and with isolating phones like those, it's impossibly annoying.
Would recommend to a friend.