Just received the Hiby W3 II today, pretty amazing for the price.
I wanted something hyper-portable, so it was between the W3 II (£49) and the BTR15 (£115). Less than half the price of the BTR15, half the weight, integrated clip, CS43131.
Power is enough for my IEMs (QKZxHBB Khan) and headphones (Ultrasone Signature Pure). I haven't tried the Hifiman HE-R9 yet, although the R9's never go outside, so I probably won't bother. Anything that isn't 'easy to drive'
might struggle with the W3 II, but it's plenty for my uses.
I'm starting to collect CS43131/CS43198 devices, so I can confirm the W3 II sounds
similar to the Fiio K11 and KA11, but not exactly the same. Both Fiios sound slightly 'better' in the highs, sharper, more energy, I'm not sure yet. It could be the difference between bluetooth and USB, it could also be the extra power of the KA11 & K11. The W3 II still sounds great and retains the lively, exciting presentation of the DAC.
I've only used the W3 II with bluetooth, LDAC at 990 kbps on desktop and 660/990 kbps on mobile. Connection has been good so far, but I need to do proper testing 'out and about'.
The Alternative A2DP driver detects the W3 II and all codecs/settings seem to be available, although I've only used LDAC so far.
I haven't tried the android app yet.
Overall, I'm very happy with the W3 II. I'll update if I have any problems or discover anything important.