I am very disappointed about the sound quality of my onboard Realtek (ALC 662) inside Linux Mint Cinnamon 17.2, so I tested the Pulseaudio Equalizer. My problem with it is, that it sets back the volume to 100% on each reboot while my standard volume is more like 50%. I tested like 10 methods I found in the web to fix that, but nothing worked at all. :-/ I am a Linux newb, so please keep this in mind if you try to help me.
Have you tried to set: flat-volumes = no in /etc/pulse/daemon.conf It would be nice to know a summary of what you have tried.
The setting you have proposed is set to *no* by default after installation. Hard to tell you how I allready tried to fix this problem, haven't made bookmarks of the methods. I played around with lotsa batch files to save the volume level at Linux shut down / restore settings after boot. Editing default.pa (can't remeber what exactly) and other stuff.
Did you try to open /usr/share/pulseaudio/alsa-mixer/paths/analog-output.conf and change the LFE and Master sections so 'volume = ignore'?