I bought the Plantronics 780 headset and it's USB. I don't have any sound card, only the built-in Realtek HD audio. When I connect the headset on my monitor's USB socket, I can hear the "ding" sound when I change the volume in the windows sound settings, but there are no applications in the mixer.
Here is a screenshot of the default audio device:
and here is a screenshot of the headset:
I'm wearing the Gigabyte GA-Z68XP-UD3, which has the Realtek ALC889 codec, High Definition Audio, 2/4/5.1/7.1-channel, Dolby Home Theater yada yada yada.
Is there anything I'm missing? How can I make the headset play audio? Is there any chance the Realtek doesn't support USB? Does the sound card even matter?