Comment 12 for bug 653446

And I do some another checks via pulseaudio console utility pactl:
I can change the volume of sink via command
$ pactl set-sink-volume 0 10000 # volume is from 0 to 65535.

When I changing it to maximum value (65535), it don't break channel balance and set 100% volume only for channel with maximum level.

But when I set volume to 0, it breaks balance :(

I created the issue about this in pulseaudio tracker: http://pulseaudio.org/ticket/874

So, at now for solve 0% problem I see only the workaround from previous post, but for solve problem on 100% you can change the volume increase method in kmix to like in gnome.