Can't get audio from USB headset or HDMI

[Steve the Pocket]

I have a USB headset that I use as my main audio source on this computer, at least when I'm in Windows, because I upgraded my video card at one point and the new one causes interference with the front-mounted audio jacks. But I've never been able to get it to work in Kubuntu. For the longest time, it wasn't even listed in the volume control, just the HDMI audio and onboard analog. More recently, I noticed that there is an entry for "Sennheiser USB Headset Analog Stereo", but it still wasn't actually usable. I pulled up the sound settings, fiddled with the preference order, set the headset to Default... still nothing. Then I tried changing it from analog to digital, because that seemed logical, and I was able to get the Test button to work... but actual programs still do nothing. Restarting not only didn't help, it caused the preference order to reset!

The HDMI, incidentally, doesn't seem to want to output sound either, although this doesn't really bug me since it was a last-ditch attempt at getting something that doesn't have interference and the colors look muddy on this display when I use HDMI anyway. I just want to know why none of my programs want to honor my audio settings when clearly the OS is able to recognize and output to it properly.

[dequire]

Without knowing anything else at this point - I would install PulseAudio Volume Meter. The package name in Muon will be 'pavucontrol'. It is a GTK+ application, but installs fine in Kubuntu and similar. It gives much more control over individual inputs / outputs and, most likely more important in your case, allows you to prioritize the USB sound card (which is how Linux sees it) over the MoBo one. If that doesn't work, report back with more specific hardware specs and Linux version and we can go from there.

[Steve the Pocket]

I was a bit stumped as to how this tool was going to help, but then I started something playing in Firefox and noticed that Firefox popped up on the Playback tab with a dropdown of output devices. I set it to the USB headset and it worked fine. And then I pulled up the stock audio CP, and it turns out it has one of those too. So apparently PulseAudio lets me set which apps go to which outputs, which might come in handy if I wanted to use my computer as some kind of mixing board, but the downside is that I have to set it manually for every app; I can't set one output as a catch-all default (or at least, it won't override the per-app settings it already defined for me). Am I reading the situation correctly?