The point is that in VDJ it will make the click through both soundcards when it syncs them, so you have to kill the sound from both to avoid it coming through the speakers, if that is the case the you need a third music source to continue the mix then make the switchover… That is why I wanted wireless HID for the next line of cdj’s then you could use your own soundcard like an Audio 2 and make transitions seamlessly as you only have to deal with your soundcard. The controller switching would have no issues especially wirelessly.