I sent Kingwa a query re firmware to clear up any confusion, response was:
We have the new firmware and driver for update the products .
Driver download: http://www.audio-gd.com/Audio-gdUSB32driverversion1.rar
Firmware update tool and software download: http://www.audio-gd.com/Audio-gdUSB32FWversion1.rar
The newest firmware is audio-gdUSB32FWversion2forDAC and audio-gdUSB32version2forDI . Choice the proper for your device, even though they can working for both devices .
It need install the driver if applied in Windows.
There is an update guide include in the folder.
The wrong operate or bad USB connect may cause the update fail and shatter the firmware, want to buy the new firmware replace in the unit.
So please read the guide careful and make sure the USB connect as well, for the table PC, connect the USB port on rear may better. Before update, restart the computer is better.