As it always goes with "too good to be true" expression, the true part may not necessarily turn genuine. So I start with the worst at the top,
CONS
1. The volume is way too sensitive, and can hardly be controlled for the normal listening sessions, i.e. it is either loud or louder. In my particular unit tuning the volume down turns off the left channel sooner than the right one, and at some point only the right channel can be heard. Seems to be fine when set to louder.
2. The input terminals are wrongly labeled (white to red and red to white). It is not a problem when discovered, but the strangest part is that connecting through the 3.5mm mini jack input or the RCA produce audibly different results. I can not be even be guessing why.
3. Although the unit sounds quite good out of the box (at the right volume) the Chinese vacuum tube is just rubbish when compared to anything other. I picked up the Electro Harmonix 12AU7/ECC82 from a local guitar shop (€16) , and the difference is day and night. Which tells me that the price this unit is sold at is in fact not the price it will sound good at.
PROS
1. Solid warm overall sound. Not as warm and pleasing with 300Ohm Sennheiser HD650 (I prefer the FIIO X5II output for it), but very noticeably better through the Beyerdynamic dt-770 (32 Ohm). The unit is apparently tuned to puts more current than the voltage out, which makes it more suitable for the low impedance headphones, and less so for the demanding ones.
2. Feels solidly built (surprisingly), and looks very nice also.
3. Can be fun at trying different vacuum tubes.
I would have given it all 5, but the loud or louder volume is a big downer for me. Basically, unless modified, the unit can not be used for the long sessions as intended.