well i dont know if they can just "go-bad" but i would assume they could over time and if your amp isnt receiving signals fromy our rca's check somewhere in your car to see if the wire got cut or it might be your amp
no it wasnt the pre out on the reciever i had actually had that happen to me as well before thats what i thought at first also, the problem was the outs on my amp unsoldered and fell off. stupid massive audio amps NEVER buy one
Massive audio amps are good quality for the price. I couldn't find anyone else who had that problem...... Let me guess, did you mount the amplifier to the sub box? lol