(Hopefully this is the right place to post this…)
I recently got a new AMD FW13 along with a pile of expansion cards, and everything worked great except for the audio expansion card, which didn’t show up as an available audio device in either Linux or Windows, and also didn’t show up in lsusb, Device Manager, or anywhere else I could find, both on the FW13 and on other systems. I thought the card was defective and got a replacement from support, but it had the same apparent issue. Then I started tinkering a little more, and discovered that the card is only enabled when something is plugged into the 3.5mm jack - otherwise, the system won’t even see the card at all.
I’m guessing this is some sort of power-saving feature to keep the card fully off when not actively in use? Regardless, hopefully this can save a few support tickets down the line… 
