As discussed in past entries, theres a significant (IMO) sound quality dropoff when making the switch from iOS to a snapdragon powered android device. With a history developing the most popular portable audio device ever (the iPod) Apple, it has means and motive to provide decent audio quality. Android on the other hand does provide support for compression-less audio, but with mostly undisclosed audio specs and
general underperformance, that means very little. You could spend quite a bit of money for an Android specific DAC but now theres another option.
The Fiio X3 (original) and Fiio X3 (2nd Gen) are two of the best bang per buck Hi-Res audio players, capable of playing back virtually every file format imaginable at up to 192kHz/24bit resolution audio. It also doubles as a USB DAC bringing that high quality audio to your laptop or PC.
Now, the Fiio is compatible with many android devices as well. If you own the Fiio X3 all you’ll need is an Android OTG (On-the-Go) adapter. To put it short, the OTG adapter basically expands the micro USB port on your phone into a full fledged USB port, which allows your device to communitcate with accessories like keyboards, mice, full size USB storage devices like thumb drives and portable HDDs, as well as the Fiio X3 and possibly other DACs.
If you have the Fiio X3 here’s what you’ll need to do:
First, check to see if your unrooted devices is compatible with OTG by downloading USB OTG Helper in the google play store
If your device is not compatible, follow these instructions to root your device.
If your device is compatible or you’ve rooted your device, head over to my favorite store ever (monoprice.com) and buy their OTG adapter for $1.47.
Update the Fiio X3’s firmware to the latest release
Navigate to devices settings and switch USB mode from “storage” to “DAC”
Plug Micro USB cable (the shorter the better) in to your compatible android device. Then plug the full size USB male at the other end into the USB female of the OTG Adapter.
Plug the micro USB from the OTG adapter into your device.
Verify that the Fiio X3 displays a screen with “USB DAC” at the top.
Plug in headphones to the X3 or your attached headphone amp and enjoy!
Tech Tourguide 
Thank you for your tutorial. I’ve done all the steps, but somehow the X3II doesn’t recognize my OnePlus One as an audio source.
Instead, it shows a message on screen reading something like “The USB data storage has been removed” with a leading exclamation mark. The message disappears for a split second only to appear again, alternating on and off.
I suspect it’s my OPO needing a different setting. I’ve used the same OTG adapter with a standard USB-A to USB-B micro cable.
Any help is very much appreciated!
Best regards.
Bernhard
Thank you for the comment! I have not tested this out on the x3II. I would verify that it has the latest firmware and that the X3 is in DAC mode. If you haven’t already, install the windows driver and verify the DAC mode is functioning for Windows. On some andriod devices you get the option to choose usb mode on your notification panel. You may look for that option and try changing it for connected devices. Hope it works out for you!
Does the X3 Ist Gen support OTG audio? I tried it with the Samsung Galaxy 3 and the Moto G 2014. Both dint work out. The Galaxy 3 managed to get the X3 to light up and open the DAC screen but no sound. Could you suggest a way to get them to work?
Hmm I was able to get this to work using the exact method I listed. Verify that you have the latest firmware installed. If you have the windows driver installed try uninstalling it. I’ve noticed that after getting the otg adapter to work with my Note 4 that I had to reinstall the windows driver to work again. I no longer use the X3 as an andrid DAC simply becuase it charges from the android device which drains the battery very quickly. You may try changing the usb connection method as well but I wouldn’t count on this as an everyday solution even if you do get it to work.
Beware: the latest firmware (1.6) disables OTG!
Thanks for the information, Mitree! I’ll update the post.