Only had this for about a month, i was playing a song at medium volume and i turned it off to leave and i hear this humming noise. so i go over to the sub turn it off then on again and its still humming. Disconnected everything turned the volume of the sub all the way down and same hum. unpluged it and pluged it back in and it makes a couple small pops and is humming...Is the amp blown? or is it the sub itself?