microphone input distortion on dj console mk4

hi,

i have a hercules dj console mk4 and the sound from the microphone input at the front is distorted. i tried 3 different microphones. same problem. the microphone sound seems to reach saturation and the sound is clipped and distorted.
could it be that i need to try a microphone with much lower impedance or could it be a problem with the mic jack or an internal problem of the console? the console output 1-2 is connected to the aux-in of a sony hifi system. 

thanks in advance for any help