Not really a digital product, but if headphone amps are what you are looking for - a company with really funny name - Schitt Audio's Valhalla is quite serious looking and interesting. It 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. Well, let us explain. 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. Valhalla delivers warm, magical sound for most headphones, as long as they aren't less than 32 ohms."
Specifications
Headphone Impedance: 32-600 ohms
Frequency Response: 10Hz-200KHz,-3dB
Maximum Output: 30V PP into 600 ohms
THD: Less than 0.1%, 20Hz-20KHz, at 1V
Topology: Class-A single-ended triode, zero feedback, noninverting, single voltage gain stage
Tube Complement: 6N1P dual triode input, 6N6P dual triode output, 1 each per channel
