Shocking stuff - laptop charger abroad

[topper]

Hmm. I'm on holiday still, and I've got my laptop charger plugged into my laptop via a typical 3-2 pin adaptor (with no earth connection). The charger's UK plug has a metal earth pin, not a plastic one, FWIW.

All has been fine until I plugged my USB audio interface into the laptop, and into my guitar. It's a Korg Pandora PX5D, which takes power from the USB cable as well as using the USB cable to input and output audio.

When I touch the strings of the guitar, there's a definite voltage there. Not enough to give me a belt, but enough to make me not want to touch the thing. It's probably worth mentioning that in a traditional setup, the guitar is plugged into an amp which is earthed. Here it's plugged into a PX5D, which is plugged into a laptop via USB, which is plugged into the mains via a charger (with no earth pin connection).

What's going on here? Is it unsafe? Should the laptop charger be earthed? It could be difficult to find a UK-Euro adapter here. I don't know much about electricity.

[randombs]

I have a feeling this is related:

I find certain metal laptops (specifically my Vaio with carbon fibre chassis and my aluminium Macbook) do that. If I rub the chassis with my finger, it feels weird, almost like a really mild vibrating feeling, but only if the laptops are plugged in (no ground wire on either psu). Also, if I have one hand on one of the laptops (either, doesn't matter which) while it's plugged in and then touch the other one with my other hand, that one gives the same sensation, whether it's plugged in or not. If I unplug the psu from the first laptop, it stops happening.

If your laptop has a metal ground pin on the plug, it doesn't necessarily mean it's connected. If the wire coming from the plug is a standard figure-8 cable then it won't be. It will most likely be used if the cable has a clover-leaf connector (3 pins) going to the psu itself.

I think it's to do with the laptop not actually being grounded, but I haven't really read up on it. I remember reading about certain laptops giving the user a bit of a static shock and I imagine it's the same thing.