Offizieller Kommentar
Hi Vincent,
It's most likely a grounding issue; since the jogs on the DDJ-800 are capacitive, if the problem ONLY occurs when the speakers are connected, they may have a short or be creating a ground loop between the speakers and your computer which is affecting the impedance of the jogs. Please try using something like an isolation transformer, or simply try connecting your computer's power supply to the same electrical circuit as the speakers.