I installed Lubuntu 15.10, all is fine. Much faster than Ubuntu, I like the minimalist interface, etc. I plug my Skullcandy Slayer (Slyr) USB headphones in, and nothing is changed. The output remains my two analog speakers.
I then tried using the 3.5 jack with my headphones, and still nothing. Audio continues playing through the 2 external speakers.
I tried xfce4-mixer and pavucontrol (pulseaudio), as well as tinkering around in alsamixer, but to no avail. I'd be fine losing my EQ if I need to use the 3.5 jack, but the same USB headphones worked flawlessly on Ubuntu 15.10... Any help is greatly appreciated!