I have an Antec 300 case and the GIGABYTE GA-P55-USB3 motherboard. This is my first build and I installed the mobo last night. I think I got most of the plugs in the right place, but my case has a plug for both AC 79 audio and HDA audio for the front port. The manual says it depends on the motherboard as to which one to use, but I couldn't find anything in the motherboard manual.
Does anyone know by chance which one I should plug in?
In all my times doing builds with the Antec 300 case (which I highly recommend) you can use either the HD Audio or the AC'97 port. Not both though. I have always preferred to use the AC '97 connection on the motherboard.
Actually I change my opinion after doing a bit more research. I would suggest you use the HDA where you can. I think I will change my case at home now.
The AC'97 connector simply extends the audio card's or motherboard's microphone and speaker to the jack on the front of the Antec or other manufacturer's case.
The HDA has additional functionality to enable "jack sensing", meaning on audio cards or motherboards with more sophisticated sound systems a popup will show prompting you to select what it was that you just plugged in. For example, it will ask if you want the connection you just made to be a "line out" or a headphone. Or whether it is a "line in" or a microphone.
HDA stands for high def audio, and you can look into it further if you like.