The hum is, in my opinion, a fault in the board that has been present since development. I spent quite some time trying to track down the issue on a friends jokerz, and by disconnecting the amplifiers and adding an external battery powered amplifier I could get rid of the hum. That was not a viable solution so we ended up with adding a resistor in series with the speakers so that you need to turn the volume up a bit. The hum was pretty unaffected by volume, so this solution made it bearable.