I think its diginal, not sure if this helps but from what i found the specs are as follows:
Audio-Subsystem
Audio+Channel(s): stereo sound
Analog/Digital Converter
(Recording): 16 bit nominal quantization
48000 Hz sampling frequency
Digital/Analog Converter
(Playing): 16 bit resolution
48000 Hz holding frequency
Microphone(s): mono sound
Loudspeaker(s): stereo sound
Audiutput: 3.5mm plug
Audio-Controller: Wolfson WM8994E
USB: USB 2.0 client, Hi-Speed (480Mbit/s)
USB Series Micro-B (Micro-USB) connector