It had been months since I had an weired issue with the embedded audio controller of my Gigabyte motherboard.
Plugin the headphones on the front panel of my box didn’t mute the output to the speakers, which nullified the purpose of having headphones.
I long thought that it was some hardware issue that I would have to sort some day by opening the box and checking the connections.
Yesterday, I decided to solve it for good and I started to google… and found out that it was a pure software issue!
The culprit sounded to be some unproper settings of the ALSA module and this Ubuntu guide just saved me.
I carefully followed the steps and it appeared that for my Gigabyte GA-790FXTA-UD5, it was necessary to this line:
add options snd-hda-intel model=3stack-hp
Ok, it did not go so smoothly as I picked out randomly models from the list until I find the right one (I had no idea of what was embbeded on my board). I hope this may help, as I have quite a lot of people with similar issues with all kinds of vendors.