First, be sure that the input levels are set to a high enough volume. For the Mic/Guitar input on the front, use the Mic/Guitar in knob to boost the incoming volume. For the 1/4" jacks on the back, use the Line L,R in knob to boost the incoming volume. After adjusting your input volume, check to see if the Record Level lights are responding. If they are, your inputs are working! If you still can’t hear your inputs make sure the output level slider is turned up.