Hi Mac ,
When i am listening to sounds that the computer makes i have done it both ways .I can use either the USB connection or use analog line cable which is split going out from 1/8 computer connection to the input 1/4 inch connection channel 7/8 on the mixer.The USB is not going through a pre amp with mid ,low and high asjustments it only lets me ajust sound shape with the Graphic EQ and not with the pre amp channel ,low ,mid and high so with the analog hook up i get the low ,mid and high ajustment besides the Graphic EQ.Again with USB connection i only get control over the Graphic EQ Becuase with USB the computer is not feeding through one of the single pre amps 7/8 input .

Regards,
Greg