Hi group. I'm on holiday, 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 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.
In this scenario, 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.
TD gurgled happily, sounding much like they were saying:
Have you actually tried the guitar into a "normal" amp? I'd be starting to suspect something awry with the wiring inside the guitar - possibly something's come loose in transit?
USB can only deliver 500mA at 5v - so there's not going to be any risk of you being fried. The motherboard or audio box thingummy, otoh...
The earthing of the power brick's irrelevant if there's no earth pin in the laptop's power connection.
More likely it's another case of the unearthed PSU having suppression capacitors between live and the chassis and also neutral and the chassis, the slight leakage means you can pick up the voltage from the chassis when touching it, but not draw enough current to be dangerous, the USB connector's shield seems to be exporting the chassis voltage to the amp and on to the guitar.
Sorry for double response. The guitar is also okay when connected to the PX5D, when the PX5D is being powered by 2 x AA batteries with no USB (or other) connection to the laptop.
On Wed, 16 Sep 2009 10:24:52 +0000 (UTC) someone who may be TD wrote this:-
I'm not going to answer your specific question, which others have done. Rather I am going to answer a more generic question of power supplies for visitors to those parts of Europe outwith the UK/ROI, using a modified version of one I prepared earlier. The links will help with trips outside Europe.
The nominal voltage and frequency is the same throughout Europe, though I gather supplies in some of the former Soviet satellites are still less stable in voltage and frequency than is the case in the west.
These days most laptops have universal power supplies anyway, which will cope with almost any normal domestic supply. As long as you can plug it in it will work.
That leaves the plug it in bit. There is a rumour that there is only one sort of electric socket on the mainland, with only the UK and ROI being the odd ones out, but that rumour is false. As well as the sockets used in the UK/ROI there are French style sockets, German style sockets, Danish style sockets, Swiss style sockets, Italian style sockets and Russian style sockets (which have smaller diameter holes).
The good news is that if your power supply is double insulated (the symbol for this is a square box inside a square box, which will be marked on any double insulated gadget) and consumes less than 2.5A then you can use the so-called europlug. This will safely fit into any of these sockets [1]. This covers most of the gadgets people are likely to take on holiday. A hair drier probably consumes more than
2.5A, but there is a larger version of the europlug which will fit into the sockets too, except for the Russian ones as the pins are too large.
Travel adapters tend to be the equivalent of a europlug. I would not use one myself, but they may be useful if you have a small gadget with built in plug, such as a phone charger, provided it is double insulated.
The pins on a UK shaver lead are too large and too close together to fit into sockets on the mainland; been there, tried that. You will need one with a europlug or an adapter. A shaver lead with a europlug will fit into UK shaver sockets.
Unless you have got a non double insulated (in other words an earthed, or Class 1) gadget there is no need to read further. While most things are double insulated some are not, including some audio visual equipment and some laptop computer power supplies. These cannot be safely used unless the earth connection is made.
The good news is that there is a so-called universal plug (the CEE
7/7) which will make the earth connection on both French and German style sockets. This has been around for a long time, I can recall one fitted to a Hoover bought in the 1960s, and it is rare to find a plug that is only suitable for one or the other type of socket. However, this plug will not make the earth connection on the other sorts of socket. If you want to use Danish, Swiss, Italian or Russian style sockets with an earthed gadget you will need the appropriate plug fitted to the lead, or an adapter lead (I have made up a few adapter leads rather than change plugs on individual gadgets).
Note that from July 2008 the Danish Government has allowed French style sockets to be installed, as well as Danish style ones. So you might encounter some French style sockets in Denmark.
There are a few travel adapters on the market which do make the earth connection in some sockets on the mainland, though I have never seen one in the flesh.
Note there are also some computer socket versions of these sockets, though these are unlikely to be seen outside offices. A computer plug may or may not fit into an ordinary socket, it depends on the design.
If you want to see what these sockets look like then
has a country by country table. It also has the official designations of the things, like CEE 7/7. The letters E and so on are a USAian scheme to classify sockets, a scheme which I think has many merits.
Should you wish to make some leads up, or buy ready made ones, then there are a few UK suppliers, like . As well as a fairly good range of leads, though for some reason not Italian (though multi system sockets are more common in Italy) they have a few components (including CEE 7/7 plugs and German style Schuko trailing sockets) and a useful table of worldwide information. I have no connection with them, other than having bought a few things from them.
The above is somewhat simplified. In some places, Italy is an example, you may find sockets which will take a variety of plugs and you may find the same thing in posh hotels anywhere. Do your research before making the trip and you should have no or only a few surprises.
A note for the lawyers. This shouldn't need saying, as it is obvious to anyone but lawyers. The above advice is worth what you paid for it. Don't rely on it, but do use it as a starting point for your own research if you wish.
[1] it even fits into UK/ROI style sockets if you know how, but it is very naughty to do that.
On 16 Sep 2009 11:58:21 GMT someone who may be Adrian wrote this:-
There are standards, plenty of them. The lead for my netbook, the lead that fits into French and German style sockets, has the markings of nine different standards organisations on it. I think I have seen things with more than nine standards marked on them, but I have neither the time or inclination to look.
any gear unearthed with a normal RFI filter will have the ground at half supply voltage via the RFI capoacitors, at a reasonable impedance.. Enough to feel, but not be dangerous. Although its capable of blowing the inputs if connected to something that IS grounded.
On Wed, 16 Sep 2009 13:43:27 +0100 someone who may be Adrian C wrote this:-
One of the other "features" of many of these systems is that an earthed plug can be plugged into an unearthed socket. Everything works and people may get away with it without a death. It is fairly common for kitchens to have earthed sockets and most other rooms to have unearthed sockets (less of a problem if RCDs are fitted), though recently earthed sockets everywhere has become the specification in many places.
Thanks all for interesting replies. I managed to get a 3-prong UK-Euro plug adaptor for my laptop, but I'm still not convinced the problem has gone away. I only had a quick chance to check it out just now. I /think/ it's tingling less. But when my upper arm / tricep touches the strings, it still seems to tingle at times, yet with my fingers it's fine. Am I going mad?
What can I do to debug this a bit further? I could get my hands on a multimeter if required. I think maybe I do need to check the earthing on the guitar itself.
surely old problem well known to caravanners: power point has reversed polarity !! Getting leakage thro' chassis etc.?
If you are in France all appliances have double pole switches; so they wire up "live" & "neutral" pins to which ever L/N feed wire they fancy.
Also note many sockets are earthed; just that there are 2 L/N pins & earth is a strip of metal down the outside of the plug that meets similar in socket.
Moral always carry a plug tester ! & a switch over cable with L & NO reversed can be useful..
Is that really a possibility? I'm probably showing myself up here but I thought that the reason that (2-pin) European plugs aren't polarized is that it doesn't matter. Is that not accurate? Does it start to matter when a device uses the earth (i.e. isn't double insulated)?
The really weird bit is that I could feel it with my upper arm but not my fingers.
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