sound card seems to be attached to motherboard. It's by IDT...

and this is your problem. 

I figured it was the integrated soundcard. Thanks to each of you for your answers and confirmation. 
 
I am thinking about the Focusrite Scarlett 2i4, it handles USB 3.0. However I am concerned that the preamps won't deliver enough gain(+55 dB max). I have two Fat Head ribbon mics and want to record an acoustic accordion, which I think needs about 65 dB gain. 

Ribbons generally want more than 55 dB. You may end up needing an external preamp. Also, most USB 2.0 interfaces are compatible with USB 3.0.