If the amp puts out a hum when all other components (except speakers) are disconnected, the problem is the amp. Turn the amp off before disconnecting, then turn it back on to check.
Breaking off the ground pin on a three-contact plug is not a good idea, and could even be lethal. Those are there for safety. If you have a "ground loop" making its way around through the power cords, it would be a lot safer to try to fix it by connecting all to the same outlet. Or better yet, get an isolation transformer.
Breaking off the ground pin on a three-contact plug is not a good idea, and could even be lethal. Those are there for safety. If you have a "ground loop" making its way around through the power cords, it would be a lot safer to try to fix it by connecting all to the same outlet. Or better yet, get an isolation transformer.