XDJ-RX2 background noise in headphones

Hi,

When I use the headphones there a very low background noise like the noise of a fan.

It is not audible when I cue a channel in the headphones or I cue the master. It is only audible when there is no sound in the headphones. When I extract a little bit the jack it seems that it disappear. 

I am not sure if it comes from the RX2 or from the headphone itself.

Thanks

Hassen