Update: Fixed the problem..... Opened the aune and notice the opamp was not completely pushed down into the socket. Also noticed that it wasn't the 2134 in there. It is the LF 353 :(

Bought one of these DAC/Headphone Amps a few weeks ago from a private seller: http://www.head-fi.org/t/438473/info-on-the-aune-usb-dac-amp   Everything worked wonderfully until today when I noticed that only one channel was working on the USB/SPDIF  (Digital) side over the headphones and...