I recently had an email conversation with Blackmagic about this topic. I initially asked them for help using the microphone and line inputs on my Ultrastudio 4K mini which I couldn´t get to work.
This is the response I got:
Please be aware that the device does not support single AES input with a microphone input, you will also need a video paired with this. When recording with the audio input a video signal is also required even if it is a black video. Please attempt to input a video signal and then add the audio with the microphone over the top of it.
My answer to this was:
Really? Who would ever need a microphone input on an Ultra Studio Device which only works with a video signal? Having a black video signal present is much too complicated for daily use.
I was considering getting an Ultra Studio 4K Extreme device as well. Is it the same there too? The Extreme has 8 XLR inputs on the back. Are these also not usable as simple Audio-in ports?
I did buy the Ultrastudio 4k Mini under the impression that it is a mobile video device where I do not need to cary an extra Audio interface for doing voiceovers because it has an XLR Port on the front.
It would have been good to know in advance that this port is basically useless…
Blackmagic support´s answer:
I have tested this workflow just to clarify and without the presence of video then there is no way to just capture the Audio input.
In regards to the UltraStudio 4K Extreme 3 this behaviour is the exact same, with all of our Video I/O videos this is to be expected.
Please let me know if you have any further questions.