Reply to Kontrol s4 noise problem

Hello wonder if anyone can help I have recently got a second hand s4 i have a problem where i am getting a static noise from the master out this happens with just power connected or just usb connected I have tried same cables and setup with my s2 and no noise at all the s4 is working and you hear it more in quiet parts of the track but it is unusable like this any ideas please ?

regards

wayne