If you have plugged your MP3 media device into the audio system and you cannot hear any music, try to turn up the volume on your device. As each media device is different, you may have to set the volume at different levels for each device you use to properly receive sound. The volume on the speakers is completely controlled by your media device and therefore requires it to be loud enough to play.
Another tip to keep in mind is that the amplifier will shut down if the volume on the device isn’t loud enough. It has a built-in timeout that will trigger if the media device stops playing, and to avoid this inconvenience be sure to keep the volume at a high enough level.