Logitech Speaker system voltage leak

[N TYPE]

I have a Logitech z906 speaker system which was only 6 months old.
While rearranging the system the other day I was feeling a tingle when I would touch the heat sink on the back of the amplifier.
Put my meter on it and was reading 100vac to earth  Im in australia we use 240v MEN system
The device doesnt have an earth pin and shows double insulated symbol on the box.

As tempted as I was to pull it apart and have a look inside i refrained from doing so and contacted the supplier for a replacement.
Recieved my brand new replacement unit yesterday and decided to test it before setting it up.
Lo and behold theres 100vac between the exposed metal and earth on this unit too, although this time I cant feel any 'tingle' when touching the exposed metal.

What do you guys make of this.. is it some sort of ghost voltage? I could definately feel some current flowing while touching it though.. similar feeling to when you would touch the antenna port on some older TV sets..

The unit is supposedly double insulated so this should not be possible, right?
Logitech is a legit brand which surely must have gone through proper certification so I doubt the design is dodgey, however it is made in china so perhaps the switching transformer has been swapped out for a dodgey local one with poor isolation.. ?

[samnmax]

Usually the tingling sensation on an isolated device is caused by a Y capacitor between the negative of the primary (after rectification) and the negative of the secondary (which seems to be connected to the heatsink in your case). Apparently this reduces electromagnetic noise but  keeps the secondary at a relatively high voltage with respect to earth ground.
BTW, this sometimes causes issues with laptop touchpads working erratically when using two-pronged AC adaptors.

More information here:
http://www.epanorama.net/newepa/2012/04/02/isolated-laptop-power-supply-issues/

[wraper]

This is not a fault and actually how most of the double insulated devices with SMPS behave.

[isopropilick]

Absolutely normal, most devices that have no physical land and so have the leak of voltage

[N TYPE]

Thats an interesting read samnmax, kinda makes sense being that its a fixed appliance which relies on signal quality.
It still astounds me that this can be acceptable though, i mean 100vac is never a good sign (even if it is a high impedance source) you shouldnt feel a tingle when touching a double insulated device! (or any device for that matter).
Kinda feel bad now for sending back a perfectly working (and non-faulty) unit for replacement.. Oh well somebody at logitech gets a free sound system