hey i got my system installed on tuesday by the guys i bought it from. on wednesday it would bump but then there wouldnt be any sound i took my car in and they said that my stock amp that was powering my speakers are blown. is there aany other possiblility why the sound is going in and out liek they messsed up on the install? i didnt change the speakers i just got subs box and amp? any info would help thanks.