Nice review, thanks for the insights. Such a shame there's no balanced in and out. Loved my XD05 when I was using it!

Between the Xduuo XD-05 + and the MOJO, which one is better in sound quality?

Very close between the XD-05+ and Mojo on sound quality, but I'd give a slight edge to the XD-05+ when combined with the burson V5i op-amp or the Muses02.

Can I connect it to my hi-fi my the Aux In / Out using a 3.5mm to RCA phono cable?
Is it USB 2.0 or USB 3.0?

mine shows as usb-2.0 and it is an XU208 chipset which I believe is 2.0 only. I cant find any documentation that mentions 3.0 so I believe this is correct. Please correct me and let me know the source if you find additional info.
Yes, you could connect an analog output to the aux-in but you would need to use a line level output on the hi-fi or adjust volume accordingly. The Optical and S/Pdif might provide a better option as they are fixed level rather than using a variable output.

I have bought an XD-05 Plus after reading this review. There is something you may be able to help me with. The front panel does not display the sampling frequency of the song playing. Instead it's just displaying whatever I change it to in the Windows setting.

That sounds like it is either forcing the bit rate in windows so that is all that is ever getting to the device, or something in the driver is failing to send the track info and is just showing the default. Do you have an android device you can test with? If so try loading USB Audio Player pro and see if it reports correctly. That should tell you if the issue is windows or the device itself.

Thanks Wijen. Yes I'm a total Android person. I'll test it with USB Audio Player Pro with my Samsung S10+ later this evening.

Also in Windows 10, there is a device: XDuoo USB Audio 2.0 DFU which does not have a driver installed. I tried installing XMOS-Driver-v4.13.0.exe from XDuoo's website but it made no difference.

I am going to be using the device exclusively with Windows 10 on my laptop. So I'd really like to have sampling frequency issue sorted as this part of the reason I chose this device.

the DFU isn't needed as I believe it only comes into play for firmware updates and mine has that same missing driver in win 10.

Just tested it in USB Audio Player Pro and its working perfectly. Correctly displaying the sampling frequency the song currently playing.

Can I check does it display the correct sampling frequency in your Windows 10? I was also expecting there to be a console in Windows where it would show information of current sampling frequency and bit depth.

I will have to look tonight as I don't have it with me at work today. - maybe PM me rather than bouncing comments back and forth too - might be easier.

For IOS users the Apple CCk is always used in DAC devices, but with lighting to usb c cables becoming common. Can we use those to plug the phone directly? The old version has a much cleaner connection for cables such as the apple cck.

Good question, I think the reasoning for the CCK was the same as requiring an OTG cable in USB as otherwise it doesn't support bi-directional communication. If I can find one, I'll give it a shot, but I suspect the CCK will still be necessary.

Tried the mfi certified micro to lighting adapter with the Micro to USB C OTG and no success. Ordered the XDUOO Lightning to USB C, hopefully it arrives before march!!!

I appreciate your extensive review and comparisons. I am interested in this but would like your opinion taking into consideration my usage.
I will use it as a desktop only , and 90% of use will be with line out to my powered speakers. When I use headphones is only with IEMs or a B&O H7. I think either the fiio q5 or maybe the previous model of this one?? I do not need much power, but want clean power, and since most usage is line out I want the best DAC . Thank you in advance.