What should i do when the output of my DDJ-SX2 is a static sound?

If the files are ok and not corrupt, try new speaker cables.  Also make sure the firmware is up to date...

I'll try it, thanks!

Also if using win 7 test your PC for latency issues with "dplcat" latency tester, if using windows 10 then you need to use latencymon as the driver structure and low level system are different. 

I found this issue often on win7 that the driver & audio software would loose sync and the results are static in the audio output. You can tweak the latency of the drivers via the ASIO control panel, this should appear on your task bar when ASIO mode is activated by your software package (eg serato, virtual dj) , some software like virtual DJ have a button to activate the ASIO control panel, first I would increase the latency value , if that fails return the latency to default and increase kernel buffers from 2 to 3, then again test and adjust latency value to get best response from your decks. VDJ 8.x also has advanced options where you can further tweak latency values and buffer sizes.