Check the level of the input signal on the 302’s LED display. Is the CLIP light on all the time? If so, reduce the incoming signal level by turning the INPUT level counterclockwise. Is the incoming signal already distorted? Make sure that your microphone is not broken, and that the mic is not distorting, sometimes vocalists get a little too close to the mic causing its capsule and/or internal electronics to distort. Most studio condensers have switchable -10dB and -20dB pads to reduce the level from the capsule before it goes to the electronics, these are almost always needed with drum over-heads and high hats.