Andre

Hi all I'm a newbie, so bare with me. My SW112 started with high rumbling noises. I thought that was the RCA cable so I changed it. It did not solve the problem. I realized that the rumbling comes with the power cord attached and the sub powered on. I tried to change the gain and other things behind it. The only solution was to put the gain to 0, but it made me not to hear the rumbling, it is still there. What should I do to solve it ? Should I take it for a maitenance ? Thanks