Hi,
there is something wrong with your configuration.
If you use the PC output, you should have selected that as the Master Out (in my case Realtek High Definition Audio).
I am attaching my configuration.
In this way, I get the "master" sound from the amplifier connected to the PC and the Cue directly from the DDJ400.
Obviously you have to activate the channel you want to hear as Cue in the Mixer section of the controller (yellow buttons marked Cue).

