All your instructions work fine until step 6, the upgrade. I have 2 X3s and both behave the same; if you press ‘back’ for a long time when the device is turned off, nothing happens. Connecting the USB lead after a while does nothing. If you try it with the device turned on, it locks up and has to be re-set. In any event, there is no option to do anything. So, the instructions are in error. Pressing the back key for a long time with the device turned off does nothing. Am I missing something here?
Also, I am not exactly sure what the ‘burn tool’ is supposed to do (that I can’t already do by connecting via USB)? One of my X3s I have had for over 5 years, and it still works and sounds great. Even though I have other, more sophisticated, devices the original X3 remains a great little device and a tribute to xDuoo design and implementation.