The Pro Box S2 is more convenient in use with the volume knob and the small display when compared to the Explorer² with the indicator lights.
The Pro Box S2 has more features, with the digital filters, and is capable of high resolution audio up to 32bit/768kHz PCM and DSD512, while the Explorer² is limited to 24-bit/192kHz PCM.
I had not used the Ether C Flow headphones with the Explorer² yet so I did a quick comparison with two albums that I know well:
- Dawn by RY X (Tidal FLAC 44,1 kHz 16bit)
- A Head Full Of Dreams by Coldplay (Tidal FLAC 48 kHz 24bit, MQA 192 kHz)
For the test I had both DACs connected to the same RPi running RoPieee, both using an Audioquest Pearl USB cable. Both endpoints were grouped in Roon so I did not have to change zones.
They both sound very good, with a slight preference for the Pro Box S2, but it would be difficult to tell the difference in a blind test.
On a few occasions while playing MQA, the Pro Box S2 briefly switched between MQA and non-MQA which is annoying as there is a significant difference in volume level. This happened only a few times, and I was unable to reproduce, e.g. by playing the specific section again. The switching did not happen earlier in the week and I have used the headphones on the Pro Box S2 for several hours every day. Maybe this was related to the endpoints being grouped and both DACs being connected simultaneously?
I’m currently running Roon Core on an HP Microserver running Windows 10 running Veeam Backup.
I have ordered a NUC7I7BNH and will move Roon core to ROCK in the course of next week.
Edit: The problem with MQA dropping to non-MQA has been resolved with a firmware upgrade to 2.12. See this thread. My Pre Box was on firmware 2.10