I have not been able to update the firmware in my ld-5. My unit will not display the message “Update Firmware! Bootloader v1.0” after turning power on with MENU button held down, as stated in the instructions (step 4) on the website. I purchased my unit in mid-February 2015 so mine may be very early production. I think my firmware might be different than units sold later.
The A-A USB cable is passive, wire only. The Prolific chip must be inside the unit so Prolific driver will be required.