Sound from Line Out - Cuts Out

Hey,

I recently upgraded to High Sierra. It took be a bit to get my sound working, but I thought I had it working.

Today, when trying to listen to music, my speaker (plugged into the back of my machine via Line Out), would play for about a minute, then do a little digital noise then quit. If I selected the Line Out again in the preferences panel, it would work for a moment, then stop.

I tried plugging it into the headphone jack in the front of the computer, but apparently this no longer functions. Everything did work perfectly on Sierra.

Any ideas?

Thanks!

Motherboard: GA-Z87X-UD5 TH