Loud Humming

About 4 minutes after turning on my system a loud hum is heard and the music stops playing. I'm trying to identify the source of the problem without having to breakdown the entire system. Any insight would be greatly appreciated. I have an Odyssey Stratos amp with an Van Alstine Ultra SL preamp,Van Alstine Insight DAC and OPPO CD player, used as a transport. Thanks!