Audio to headphone amp via USB

[TheRogueOne]

Does anyone know of a way to transit audio via the USB cable from an android phone? Perhaps with the aid of a dedicated circuit?
I simply wish to play audio from my phone through my headphones (using a headphone amplifier) via USB instead of the audio jack.
Being a student (i.e poor), I'm planing on building a headphone amplifier and have have considered powering said amplifier via the USB output of my phone instead of lugging around 9V batteries. Of course, this can be done rather simply if it were just for powering - though if that were the case, I'd have a second cable coming from the audio jack output (which is obviously rather annoying).

 

[disfunctionalshadow]

You'll need and OTG (On The Go) cable, probably a powered hub and at least Android version 5 os.

 

[DF96]

Does an OTG cable include a DAC, or is it just a bit of wire with connectors on the end? Or does the headphone amp include a DAC?

 

[mrWagner]

You have to check your phone specification.
OTG is just a cable. Also have to mention that phones can't detect every dac. You also need driver on the phone for them.
If you have DAC in you phone, then the sound already comes out on jack as it is already Analog.
Your phone would send out the digital data on the OTG cable and your dac makes it analog. Just like a PC. It sends out the digital data on the USB cable.