Electrical Shocks when Speakers/RCA cords plugged into DJM-900Nexus

Hi Guys

Hoping someone can point me into the right direction where to proceed with this annoying issue I'm struggling to isolate.  The shock is continuous in nature and although not a big shock it's enough to surprise you when you get hit.

So I have a DJM900 Nexus with 2 x CDJ2000 Nexus's and 2 x Traktor D2s connected to a laptop and speakers. I am in Australia using 240v

Now when I have it all plugged in and setup I am getting a slight shock when touching the metal screws on the mixer.

This only happens when the laptop isn't plugged into mains power. If the laptop is plugged into power then the shocks stop. The shocks occur through all CDJ's, D2's and the mixer.

Now to isolate the issue. I've tried plugging in the mixer by itself. No shocks received. I did the same with the D2's and the CDJs and by themselves no shocks occur. I tried the same with the laptop and nothing happens. 

Furthermore I tried several powerboards and several power outlets in the house.

Now I think I have gotten it down to it only occurs when the speakers are connected. I have tried two different lots of speakers (FYI just using 5.1 logitech setup) Also tried a 2.1 set of speakers from my computer. I then tried a friends logitech 2.1 setup as well.

When I unplug the speakers the issue goes away.

Any ideas how to solve this or what's faulty?