What caused my Motherboard to spark?

I just got myself a new antec 900 case and everything worked fine until I plugged in my headphones. No sound came up on the headphone and the speaker. I restarted that pc and I now get the message "No audio output Device is installed" I reinstalled drivers but I get "Device object not present" Then I opened the motherboard and plugged ac97 on F_audio. I only plugged HD audio before but now both is plugged. Booted the computer and I still get the message "No audio output Device is installed". I plugged in the headphones and I heard a quiet sound(I think its a spark) and then I smell a burnt smell coming from the motherboard and I turned quickly unplugged the cpu. I waited for a bit and started up the computer and everything runs fine except the audio. I am now scared to plug in the headphones. I think the onboard sound fried or something. But I don't see any burnt marks on my mobo.
Should I just buy a new soundcard or a new motherboard?
I'm also worried about that burnt smell but other than that everything seems to work fine except the sound.