In standard USB audio, a PC / Mac / Galaxy S3 / Galaxy Note 2 operating as a USB host (i.e. a USB A-device) interworks with a USB DAC operating as a USB peripheral (i.e. a USB B-device).
The Galaxy S3 / Galaxy Note 2 is a USB On-The-Go device.
A USB OTG device can act as a USB host or as a USB peripheral.
Simply put, a USB OTG device like a Galaxy S3 / Galaxy Note 2 can act acts as
. a USB peripheral when a Micro-B plug is inserted [regular cable]
. a USB host when a Micro-A plug is inserted ["OTG cable"]
S3 as USB peripheral:
. S3 – regular cable – PC / Mac as USB host
. S3 – regular cable – upcoming specific Android Jelly Bean-compliant USB DAC as USB host
S3 as USB host:
. S3 – "OTG cable" – USB mouse as USB peripheral
. S3 – "OTG cable" – standard USB DAC as USB peripheral
where
"OTG cable" = micro-A plug + USB cable + micro-B / mini-B / type-B plug
micro-A plug to be inserted in an A-device (i.e. a S3)
micro-B / mini-B / type-B plug to be inserted in a B-device (i.e. a standard USB DAC)