Sound problem (treble, bass balance)
 

I have a problem with sound on my user account. This only happens on my user account. And here is the problem, it seems instrument quite louder then voices, that are lot quiter. This appears no matter which sound system(plugin) I use, Arts, ALSA, OSS but it doesn't help? Why is this happening? I think the problem may be in the bass/treble balance but i'm not sure where could I chage this?