I've tried the putting a piece of plastic between the cable ground and it still has the same problem. I'm going to go and buy the line filter tomorrow and try it. Also I have 2 subs running. When i connnect the second sub from the line out of the 350 i have the same problem with the other sub as well. But if i connect the other sub direcly eliminating the 350 it doesnt hum. Is this normal?

Thanks again