The sound coming from all of the speakers is staticky and muddled. About 8 months ago, I was getting a whirring noise under my drivers seat. I removed the seat and replaced the fans on amp. A couple of months ago, the stereo started a random popping crackling noise when off and the same staticky sound when on. It stopped one day and worked normally for several months. This past week, the sound issue came back (without the popping and crackling when off). The fans I installed on the amp appear to still be working. What else should I look for to fix this issue?