As far as I understand, was the optics delivered to all dudu, including the 6 series?
I still can't use a pure signal not from Spdif, not from USB.
USB audio is generally a separate topic for the campaign, really no one is faced with the problem of the inability to output sound through an external DAC, on the same Amanero it is simply missing. The rest of the DACs just crackle and clap.
The external devices work great with my Pixel7 and Fiio JM21, but I bought the dudu6 only because it supports USB Audio and in the hope that I would get rid of unnecessary inconvenient devices. Sadness.