Comment 15 for bug 883485

Just to mention that, I tried what Alex (#14) proposed as well (i.e. also setting /sound-card to PlaybackBuiltin...), but that resulted in xfce4-mixer only showing one channel, which controls the PulseAudio Master Volume.
If you want to retain control over all Alsa Channels it's better to solely set /active-card to Pulse.

One little regression I forgot to mention is that the unmute-button in xfce4-mixer doesn't work anymore then (seemingly instead of the multimedia-button unmute). But personally I feel this is a minor issue, hardly anyone will use that directly because the mute/unmute function is present in indicator-sound directly.