dude what it sounds like u dont have the amp wired right you said it was a older amp what ohm rating are ur subs and and what can the amp do alot of older amps cant run in 2 ohms and can check how many ohms your subs and putting out with a volt meter and it can also be a bad ground or the power wire is too small and cant get the wattage needed to run the amp.Just trying to help look in to these things.