Play on computer speakers while prelistening in DJ controller built-in audio

Most DJ software let you play the mix on computer speakers while using the DJ controller built-in audio, at least for the preview. 

In Serato:

In Djuced,

• go in Settings > Audio

• as Audio device, select the dj controller built in audio interface

• as Output, check the outputs of the DJ controller for Master and Headphones

• In “Send master to computer speakers”, select the computer audio device

In VirtualDJ

• Go in Settings > Audio

• In the Outputs thumbnails, check Speaker+Headphone

• In Hardware thumbnails, select the DJController with built-in audio

• In Outputs lists, you should see the Master and the Headphones of the controller

• Click on + sign on bottom right of the Outputs list

• Select the computer audio interface as Master output