I have a strange problem. It just happen recently, when I accidentally unplug my headphone. But I unplugged it before and nothing happen. Basically now, when I use my headphone through front jack, when playing videos, I can't hear voice. Only background music. Using kde sound setup, pressing front left and front right test button, result in a mono sound. No distinction between right and left. This only happen with front jack. Rear jack is working fine.