To update the firmware on your Denon AVR-X520BT you must use the on the front panel
: Plug the USB drive into the front panel USB port of the receiver. Enter Update Mode : Denon Avr-x520bt Firmware Update
While holding them, press the button to turn the unit on. Initiate : The display should show " USB Update Start ." Press ENTER on the remote or the main unit to confirm. To update the firmware on your Denon AVR-X520BT