Like most modern desktops, on KDE it is possible to change the volume by hovering over the sound icon in the tray and moving the scroll wheel.
But my video card also seems to have a built in sound device (HDA NVidia Digital Stereo HDMI). I never use it, but for some reason, it is the device which is mapped to the convenient volume icon. So, when I want to change the volume, I have to open the whole window with all playback devices and move a slider there, which is especially unpleasant when I start a very loud recording at 2 AM and want to quickly turn down the volume before I wake all neighbours.
So, how do I map the icon to the real sound card?