Valhalla is a Class A, single-ended triode headphone amplifier with no overall feedback and noninverting circuit topology. It provides classic tube sound and can drive headphones with impedances as low as 32 ohms.
Yes, we know that all you got out of the preceding paragraph is probably, "Classic tube sound." And if you're not a tube junkie, you might not even know what that means. Some people say tube sound is a smoky nightclub with a hot chick in a red dress, it's a warm swimming pool in summer, glowing green against the purple twilight, it's a . . . well, hell, you can't really explain tube sound. Think "smooth, fluid, liquid, alive." But not in a SF-movie-gonna-eat-you kinda way.
All Tube, All The Time
The only active devices in the audio signal path in Valhalla are tubes. The 6N1P triodes input provides linear, low noise voltage gain. The 6N6P triodes provide good power output capability for a wide variety of high-impedance headphones (though, if you're looking at orthos, check Mjolnir, Lyr and Asgard instead.)
High Quality Parts
Don't compare Valhalla to cheap tube amps using open-frame carbon pots and substandard parts. Compare it to tube amps using Alps Blue Velvet pots, Dale resistors, Wima capacitors, and other top-end components. Also consider that Valhalla has almost 2,000uf of filter capacitance in its oversized power supply, for superior performance.