When you play a test sound in the phonon settigns, it is always played at 100% volume. This is in particular a problem when using PulseAudio, as it will set the overall volume to 100% when flat-volumes=true which is the default. Reproducible: Always Steps to Reproduce: 1. Select the output device 2. Click on "Test" Actual Results: Test sound is played with 100%, if using PulseAudio the overall system volume gets set to 100% too. Expected Results: Test sound should be played at a sane volume, it should not change the overall volume. Or at least the volume should be changeable. This happens with both the gstreamer and the vlc backends. I'm using KDE 14.12.3 at the moment, with Phonon 4.8.1, but I can reproduce the same in Plasma 5.2.2 with Phonon 4.8.3.
This is actually the same as bug#346614, which got reported later, but has more comments. *** This bug has been marked as a duplicate of bug 346614 ***