High pitch noise coming from subwoofer

Ok my car is a 1991 Acura Legend and I have a xtant x1001 and a JL 12w7. I have a high pitch nosie coming from my sub when it is on and actually the sub doesn't even work accept for that noise, and it pops when I turn off my car like many subs. My amp light is on though and all wires are connected, what could this be? It is not ground noise because it is not constant it goes up then off in like 2 second intervals. I know my amp has power and since my sub still pops when my car turns off I assume power is getting to the sub. Could there be problems with the signal? I have no clue on this one guys. I also recently jumped my car with my stereo attached and my subs started going kinda crazy when the power was going through them, could this have contributed?

check your rca's

Checkthe ground to make sure it's still tight.Cause I'm So white and nerdy...

First Class Certi-fried installer