I might be being a bit stupid here, but why can't you just use the headphone port? I assume this is not good enough quality for you or something?
Motorola RAZR HD XT925 (Canada) ~ CM11 M8 ~ TWRP 220.127.116.11 (DHacker build) ~ ART ~ Moto 3.0 Kernel
Google Nexus S i9020 (World) ~ CM11 M8 ~ CWM 18.104.22.168 ~ ART ~ Guru Kernel 0.9.4
LG G Pad 8.3 V500 (USA) ~ Stock Android 4.4.2 ~ Stock Recovery ~ ART