I have just purchased a used Aguliar DB750 and was out playing a job last Friday without any problems. then yesterday, after playing with my band for a few hours the cabinet starts to make a loud noise as if the units was blown. I tryed to connect the amp to another amp and the same problem again. It's like the amp can't handle the vibration from the cabinet because when the amp stands beside the cabinet, instead of on the top, there is no problem. Do anybody know what the problem can be??