can I ask please some questions
1- can you root and install viper4android
2- how does the onkyo sound signature compare to a fiio x7 with am3 or am5 amp modules, as right now I am finding the fiio x7 a bit bright for my liking and enough bass
3- how is the sound stage compared to fiio x7
4- can I connect it to mojo, although I will not do it on the go but I just want to make sure that I can connect it to mojo if I need to
5- what is the difference between DP1XA and DP1X
For (1) - If you do a search, within this thread, for "fastboot", you'll find posts with links to the TWRP and SuperSU downloads, as well as the steps for how to unlock the Bootloader if it's locked (mine wasn't), and how to install the TWRP and SuperSU. As an aside, the fastboot command, when running within a Cygwin64 Terminal on Win7, didn't see the DP-X1, but it did when running within a regular Win7 Terminal. The various adb and fastboot command I've used in the past on my Nexus 5 and Nexus 7, were run from the Cygwin Terminal.
There are several threads on the XDA Developers Forum which deal with installing the various versions of viper4android on different versions of Android. I've got the Version 2.5.0.5 (FX), Codename "Beautiful" installed and working on my DP-X1 (Android 5.1.1). It's been quite a challenge to get viper4android running on my Nexus 5 & 7, which have CM13 (Android 6.0.1). The first attempt, with viper4android 2.4.0.4 seems to have worked - but then I tried updating to 2.5.0.5, and now it will install and enable, but not process audio on either of the Nexus devices - and trying to go back to 2.4.0.4 hasn't resulted in audio being processed as it was before...
The only other DAP I've heard so far, is the Shanling M1, which isn't in the same price/performance league as the DP-X1 or fiio X7.
For (4), the DP-X1 apparently can output digital audio via the USB connection to an external DAC (but Onkyo has never released a proposed firmware update to allow it to operate as a USB DAC).
For (5), you may have to take a look at Onkyo's website (possibly the Japanese site).
Take Care,
David Baldock