Using US mains leads? What about mains polarity?

Penance posting this link on Friday reminded me I meant to look into the mains polarity issue with my Shunyatas:

http://www.handymanusa.com/articles/polarity.html

It appears that on a standard US mains socket the live and neutral are the opposite way round to UK wall sockets. US IEC leads are consequently wired to swap over live and neutral (relative to UK IEC leads) so that they are the standard way round upon reaching the IEC inlet on the back of a piece of equipment. Or at least all of my Shunyatas are and I bet all others are too.

Using a single US mains lead plugged via an adapter into a UK socket therefore presents mains with reverse polarity to a piece of kit. That is, the live goes to the neutral and vice versa.

So the question is, does anyone do anything about this? It's less safe this way, and I know at least some people worry about having figure of 8 leads the 'right' way round to get the best sound, so possibly there are sonic issues too?

I reckon I'll make up a US wired IEC lead to feed a distribution block into which other US leads are plugged, which will get the polarity right again, but I was wondering if anyone had any comments? Does everyone just ignore/not know about this or what?

Martin

 

mains polarity

Hi Martin,

My understanding is that it does not matter at all, in terms of electricity and powering the kit, but it certainly does matter in terms of sound - at least to get all kit at the same polarity

The mains input goes to the mains transformer, and AFAIK this is where it gets difficult - there is no way to easily distinguish the internal connections, so no-one bothers, and just connects as they feel on the day. Most detachable input plugs are figure-of-eight anyway, so can easily be connected either way around, as you suggest in your post.....

I seem to remember a device that could look at the incoming poloarity into the kit and deduce whether it was neg or pos polarity defendant upon the field generated (pls note that as the kit is not marked this is not the same as checking it at the mains outlet) - do any other members have more info?

Simon

P.S. - I agree about Southampton - lived there for a few years now and am constantly amazed that it manages to get even worse, year on year.....

 

Unfortunately all the HiFi kit I own, and for that matter all I've come across, has three pin IEC mains connectors which are not reversible.

For what it's worth, from an admittedly naive perspective, it seems unlikely to me it'll make any sonic differences but it does clearly have safety implications.

Yup, heard of them too. Seems a little pointless given you can just check continuity with a multimeter, which I suspect would be cheaper to buy if you didn't already own one.

 

Martin, you cant check AC polarity with a multimeter unless you check from line to earth, but that tends to throw RCD's if they are fitted in the consumer unit.

 

Ah, right, there's clearly something I'm missing here... (not a great surprise there!). What I was thinking of was checking continuity to see which pin is live and which is neutral, and was taking which way round these were to be referred to as polarity. This will be what will be swapped by changing the way round you plug in a figure of eight connector, and I thought that was described ss swapping polarity. What does polarity actually mean in this context?

 

Martin, you're correct. Your description is what I think of when talking about mains polarity. You can test polarity using, ermm... a polarity checker . If you have one of those electrician's screwdrivers that have a little orange light that glows when you stick it in the mains, that's a polarity checker. It will only glow when you touch "live" with it and not with neutral (or earth).

If you have your mains cable plugged in and are holding the IEC plug end, looking at the IEC end head on with earth at the top, the terminal that should be live is the one on the right.

Michael.

 

Ill try to explain, but been a long time since i practiced this stuff.

On AC there exists a potential difference between Live and the return, return could be neutral or earth. No voltage exists untill a load is applied between live and return. Return itself does not have a potential difference. When the load is applied the alternating effect of Ac happens. So if you touched the live, you would feel it, touching neutral or earth you should not feel it. But if there was a load between live and neutral you would feel it.So you could check polarity by useing a multimeter between live and/or neutral and other lead to earth, only the live when tested will show a voltage. Neutral should have no potential difference to earth.
In relation to mains connection, as others have said, it is more a matter of safety that live is switched/fused.

 

Cheers for clarifying Penance. My multimeter method was simply one of checking continuity between contacts at the two ends of a cable, not connected up to anything. Provided I can safely assume my wall sockets have been wired up the right way round this is then sufficient for me to work out which is live, and which is neutral, and therefore know if these are being connected up the right way round to a component. As well as not needing any fancy lights it means I'm not doing any measurements with mains voltages present, which makes me much happier.

 

There will be voltage present if you make contact with the live.

 

That's not going to happen unless I jab the multimeter probe into the live of the mains socket!

You're missing my simple minded approach...

Imagine I take my mains cable out into the garden, well away from any mains supply, with my multimeter, and see which of the IEC end contacts is wired up to the pin on the plug end that will go into the live terminal of a mains socket. That way I know which will be live when it's plugged in.

 

Sorry Martin, I did miss your point:shame:

 

If your leads are truly reversible - like the 'AC Telefunken' figure8 connector, then I would advise anyone to try reversing the connection, while the device is connected to the rest of the system. If you have a preferred polarity, mark it on the mains connection [dot of correction/nail varnish on the plug + socket]. You can also measure the case to case voltage with a multimeter. Logic says that the lowest voltage between device cases is a 'good thing' but it's the sound we are trying to aim for. The same could equally be applied to 3 pin polarised connections [which if sold abroad would simply have attached whatever unpolarized mains plug is used in wherever..]. The difficulty is that, if the manufacturer has attached a polarised mains like in the UK, and you reverse it - you are now responsible for any issues that arise.

 

Indeed, which is efectively the issue I have using US leads at the minute, and why I'm going to get round to sorting this out in my system soon.

 

I've never heard of any issues arising from connecting any equipment (hifi or otherwise) to the mains with "reversed" polarity. In most of continental Europe even earthed mains plugs can be plugged in either way around so there's simply no way to know if you've got it right unless you use a polarity checker....and it's only detail obsessed audiophools that bother with that.

As to whether it makes a difference to the sound, I haven't heard it. I do now have all my hifi gear connected up the right way (audiophool ) but I can't say I noticed any difference. Even the people who claim to hear a difference say it's OK as long as all your kit is connected up the same way, regardless of the actual polarity (allthough if you're going to check every plug, you might aswell do them all the right way).

Michael.

 

This is true. Modern consumer goods are wired to 'not care' safetywise. If you were making an amp yourself in the old days, you may be tempted to put a fuse in the live primary wire [in case of a transformer short]. This would therefore be safer the right way round.

Nowadays, consumer goods have extensively tested/designed transformers and can therefore be connected any way round without a direct mains connection possible to the case during a fault, or the low voltage circuitry [Class 2 ie double insulated], so they can be sold internationally. This doesn't mean there may not be sonic benefits [theoretically] from one orientation, and it may not be the way the manufacturer chose when he soldered the wires on. Maybe you have a piece of kit which DOES need to be the right way round and you want to find the best orientation in whatever else is plugged into it [as you say Michael, it is the relative way round between item A and B that could change the sound not the absolute orientation. Some of this is due to ground currents/transformer induced currents. Maybe its also having applied voltages on dielectrics [insulators]. It could have an effect on digital copper conections too. I did once informally experiment on my kit, and did draw results, but it was hardly generally applicable. If you have a preference for one way or the other, you simply mark a polarised plug and socket accordingly [eg dots of correction fluid].