Gosh, Z was right about that TA-22! I’ve had this with me for a few days now and am impressed by its qualities, especially with headphones from the upper mid-range.
With both the Arya Stealth and the HD800s, this DAC/Amp does exactly what is needed to make both headphones shine, smoothing out the range that occasionally makes these headphones sound a bit harsh without even remotely missing detail to permit.
It opens a realistic stage in all directions, wide, deep, high, thumbs up for it. He also manages to provide both headphones with a clean and very solid bass reproduction, which few amplifiers can actually achieve, especially with the Sennheiser.
As a result, the Arya suddenly sounds silky and almost realistic and retains its attention to detail without drifting into its usually rather “technically sterile” reproduction pattern.
The HD800s shows its qualities completely and in this combo reminds me why I love the Senni so much!
By the way, for Sennheiser’s 650 it’s all a bit too much of a good thing, it tends to sound rather dull in combination with the TA-22, with slight distortions in the bass range, while both the 600 and 660s benefit from the interaction.
The sensitive menu navigation through the rotary control mentioned by Zeos is no longer up-to-date, since the menu navigation has probably been improved and the rotary control now has a gradual grid, similar to the Topping A90D.
I would also like to mention that the amplifier didn’t passed the Andro test, which means it is definitely not dead quiet in the low/gain area, in combination with the hypersensitive Andromeda.
But if you have headphones or less sensitive in-ears that tend to be a bit high-pitched and/or could use a little bass boost (like 80% of the ChiFi goods 
), here you go, the TA-22 exists.
All thumbs up from my side 