I followed the tutorial mentioned here but after the sound is much quieter even at 100%. I have loooked at the Pulseaudio volume controls and alsamixer and they are all also at 100.
I faced the same problem: I've used
I've found out that if my volume level was, say, 30% before I've started QJackCtl, it seems to think that this is the max volume it can get, so this volume will be 100%.
So I just turn volume to maximum and started QJackCtl and now sound volume is okay.
Hope this helps.
I have found that it's the alsa mixer that had the headphone volume down to 0. all I had to do is start alsamixer, select my sound card and up the headphone volume. hth