look for an otg usb cable, something like this:
Edit: Beaten to the punch ;)Warning: Spoiler! (Click to show)
New USB DAC/amp: Creative Sound Blaster E5, a standard USB DAC and an Android-specific USB DAC!
Standard USB DAC & Android-specific USB DAC:
A standard USB DAC acts as a USB Device.
A standard USB DAC can work with a PC, a Mac or an Android-powered device acting as a USB Host.
An Android-specific USB DAC acts as a USB Host.
An Android-specific USB DAC can work with an Android-powered device acting as a USB Device.
An Android-specific USB DAC can't work with a PC or a Mac, because a USB Host can't work with another USB Host: USB is a master-slave communication bus, USB communication can only take place between a master device (i.e. USB Host) and a slave device (i.e. USB Device).
An Android-specific USB DAC is compliant with the Android Open Accessory protocol 2.0:
"Android Open Accessory protocol 2.0 includes optional support for audio output from an Android device to an accessory. This version of the protocol supports a standard USB audio class interface that is capable of 2 channel 16-bit PCM audio with a bit rate of 44100 Khz. AOA 2.0 is currently limited to this output mode, but additional audio modes may be added in the future."
According to the Creative web site, the Android-powered devices which have implemented the AOA 2.0 protocol are as follows: Google Nexus 5 / 7, Samsung Galaxy S4 / S5 / Note2 / Note3, Sony Xperia Z Ultra, Xiaomi Redmi / Redmi Note / Mi3, (LG G3).
E5 as an Android-specific USB DAC: thru USB HOST port
Xiaomi Redmi Note >> regular USB cable >> USB HOST port > E5 >> headphones
E5 as a standard USB DAC: thru USB port
Android device >> USB OTG cable >> USB port > E5 >> headphones or
Android device >> micro to standard USB OTG adapter + regular standard to micro USB cable >> USB port > E5 >> headphones
USB Audio Player PRO (UAPP) should play a 24/192 music file and output a 24/192 PCM stream towards a 24/192 capable Creative Sound Blaster E5.
Currently SG$199 (i.e. US$160).
"From 28 to 31 August 2014, the Sound Blaster E5 will be showcased and available for pre-order at just SG$199 at Comex 2014 (Suntec Singapore Convention & Exhibition Centre, Hall 601, Booth 6141 and 6801).
After which, the Creative Sound Blaster E5 will be available through sg.creative.com and all authorized Creative retailers from October 2014 for SG$269 (US$199)."
iFi micro iDSD USB DAC/amp & Sony Xperia Z2: