The A1 is suitable, unlike the X1 exclusively for Android devices with USB OTG connection or for connection to a Windows or Mac PC. I have tested the A1 with a Samsung Galaxy Note 3 and a Windows 7 PC.
In conjunction with the Samsung Galaxy Note 3, you can purchase the USB Audio Player Pro (around 5.00 EUR in PlayStore). Normally, it is recommended that first preparing the OTG connection via USB, the unit turns on and then only the USB Audio Player Pro starts. However, this has the effect that you only hear choppy digital shreds. Here then, for example, "File DAC 96000 Hz, 96000 Hz" is a song with high-res display correctly. But as I said, the sound is completely disturbed. I wanted to pack up the equipment already and return when I finally generated a clean sound with some back and forth. And I proceeded in the following order:
1st switch position on the rear panel to "Android / Line In"
2. Connect USB OTG
3. USB Audio Player Pro Open (ignore error message)
4. In the Settings of SW player the "Force 1 pocket per transfer" option select (must be done only once)
5. gadget / device again (important!)
6. Only now start a track
The procedure described generated finally a clean, well-resolved sound with punch and nice spatial resolution. All thing I noticed that was above Audio Player song now "41100 Hz, 96000 Hz File (red) DAC" displayed per the same high-res only with the USB. Similarly, only the upper right 48000 Hz LED lit up on the device. I researched again in detail on the manufacturer's website and found the following entry:
"Android Device digital connection: sample rates will indicate at 44.1kHz or 48kHz when connected with USB OTG cable"
It will therefore play no higher-resolution files in full via Android-OTG. That was me at first not clear. However, one must note that the excellent sound characteristics of a high-res file sonically nevertheless reflected compared to FLAC files in normal CD quality in a positive way.
The handling via Windows 7 PC, however, was a little easier. I use the Media Monkey as a software player and have an ASIO driver (normal) downloaded from the ADL website and included as output plugin. Now all high-res formats have been resolved correctly and displayed properly even on the device. The sound is excellent. Great resolution, good timing, rhythm is right, bass have Punch, heights are not overemphasized. Very nice.
Conclusion:
+ Very good sound via Windows PC
+ Complete cable set
+ Light and handy
~ Sound via Android ok, but can the competitors (Fiio E18) for significantly less money as well
~ Processing ok, but not outstanding
- User handling unnecessarily complicated (but may be better also in interaction with other smart phones - Feedback happy)
- Restriction to 48000 Hz via Android
