DDJ RZ No sound in headphones

Well since i don't have power up speakers this is what i did i have an amplifier which has an XlR input and those big jacks for the output for speakers not sure how many M.M are they  so i used Xlr to 3.5mm jack cable and connected the amplifier to my laptop with and usb sound card as my laptop headphones jack is bit broken 

Now everything is working fine i am getting a signal on the channels and the controller is working fine but i don't have signal in Master and my headphones doesn't work i have changed the setting in the Rekord box so it transmit the signal to the speakers using the sound card which is connected to my laptop and everything is fine but no master and Headphones signal HELP.......! please