Playable bit rates? I didn't see it mentioned here or on their website. Looks cool, though.

It's pure amplifier, no DAC function. so, it doesn't care for bit rates

This thing looks too good to be true. 

~Very nice!

Looks good, sounds good from what I've seen here. I'm gonna look into getting one.

Opamp-free design is interesting.

I'm not sure it's opapm-free. Aune declares that output stage built with discret triodes, but may be they're using opamps in preamp stage. I'll ask for more details

Really great pictures! Very nice photography!
For an external headphone amplifier, 50 mW @ 32 ohms is rather too low. But it is justifiable if it has unique sound signature that worth the additional bulk.
Nice review!

thank you. please note, that this amp is pure class A, so on higher impedance loads it produce more power

@cleg yes that's right, class A, that's why I said it is justifiable if the sound quality is very good and really improves the listening experience.

pics on their site you linked to looks like there are no opamps. Did you try it with any sensitive IEMs?