Hi MozZ,
If you have a new gld-80 it will not play mp3’s check the knowledbase http://allen-heath.helpserve.com/Knowledgebase/Article/View/451/124/gld-what-codecs-are-supported-for-usb-audio-playback, older desks will.
Cheers Dave
GLD-80
AR2412
GL2400-24
MixWiz3
