Hello. I recently switched from a cheap external capture device to AVerMedia's Live Streamer Ultra HD, and I seem to be having the same problem with this one that I had with that first device (though when I started using said first device, OBS was able to capture audio from it.) OBS, for whatever reason, doesn't want to capture audio from my Switch 1, which is hooked up to it. I've tried changing the Audio Output settings for the source, I've tried adding the card as a Mic/Auxiliary Audio selection, I've tried removing and re-adding the source, I've made sure the card has the latest firmware update... I just can't seem to figure out how to capture audio consistently from my Switch. Tomorrow, I plan on swapping out the cable that goes from my Switch to the card with the one that was included with it and see if that fixes the problem.
One thing that I'm continuing to learn about streaming is that it can get complicated if there's a problem, lol.
Here's some added information that might be helpful:
-The card has two HDMI slots, an IN slot (from my Switch) and an OUT slot (to an HDMI switch, since I switch back and forth between my computer and the Nintendo Switch.)
UPDATE: I seem to have found a most-likely-temporary solution. What I did was change the Audio Output setting for the video output source to DirectSound, close OBS, reopen OBS, and change the setting back to "Capture audio only".
UPDATE 2: It appears that I have found the problem. When my Bluetooth headphones are connected to my Switch, the audio is sent there instead of to both the headphones and OBS, and it is only sent to OBS when they're powered off.