I have a Line6 UX2 recording interface where I can record my guitar/and mics thru my computer’s USB port, but I also wanted to record an additional mic through the actual mic jack on my computer.
Is it possible to record both the UX2 through the USB port and a computer microphone through the microphone jack at the same time?
No. Sometimes, under special circumstances and on some machines, you can run more than one soundcard connection at once, but rarely two different devices. Some Macs and I think Linux can force two USB devices to run at once as one, but you can’t separate the voices later and they slowly drift out of sync.
EBay your sound device and get a bigger one – one that has enough microphones built-in.