No signal, No sound

Just got my DDJ-400. Connected it to my laptop and connected my powered bookshelf speakers as well. It worked great. I disconnect the powered speakers from the controller. I than connect the controller to my amp. My amp has my passive speakers connected, but there was no sound. I checked the indicator lights on my amp and it doesn't show that there is a signal coming from my controller. I disconnected my amp from my controller and reconnected the powered speakers to the controller. Once again it work perfectly. When I connect the controller to my amp to push sound to my passive speakers, what am I doing wrong? Why does my amp show there is no signal from the controller? I'm in need of technical help. Thanks...