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Electrics in the project studio - Using extension leads

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Electrics in the project studio - Using extension leads

Postby BH12neil » Sat Jul 15, 2017 1:03 am

Hi everyone,

I'm new to this forum and this is my first post.

I have been reading articles on this website about powering all kit from a single dual wall socket and I have to say I am confused. Articles I've read here recommend a star formation with extension leads is a way of avoiding ground loops, but elsewhere on the net I've read that plugging extension leads into other extension leads is dangerous. I understand the concept of overloading wall sockets and what may happen as a consequence which is fine, but the star formation as I understand it is effectively 'daisy chaining' albeit in a different way.

Am I missing something here; can someone explain the 'star formation' and its practicalities.

Cheers

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Re: Electrics in the project studio - Using extension leads

Postby ef37a » Sat Jul 15, 2017 5:29 am

Hi Neil and welcome.

The reason for running all the gear back, ultimately to a single wall socket is so that there is but one mains earth path. Discussions about earth loops etc can get complicated but having a single power point is the best first step.

Safety. I know electricians do not like an 'extension into an extension' I am not really sure why. If the primary extension is of the proper current rating and properly fused I can see no problem. I do agree it looks messy so maybe Sparks as a breed are OCD tidy?

All that said, DO buy quality products. The £3.99 six ways from Rock Bottom are not recommended. Look at CPC and others. The diss strips that get fitted to network cabinets are of excellent quality. If you feel qualified you can buy the strips and fit custom length cables. Avoid if you can strips that are touted as 'surge supressed and filtered' They rarely are needed in UK, do no good that I can see and can, in some circumstances, make ground noise worse.

Lastly, do not worry about loading and safety. Even a very big studio rig would not come close to the 13A limit. (that excludes things like lights, heaters or 2kW power amps!).

Just occurred. Power poles/pods are a neat solution.
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Re: Electrics in the project studio - Using extension leads

Postby ef37a » Sat Jul 15, 2017 5:39 am

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Re: Electrics in the project studio - Using extension leads

Postby Mike Stranks » Sat Jul 15, 2017 7:33 am

ef37a wrote:Hi Neil and welcome.

The reason for running all the gear back, ultimately to a single wall socket is so that there is but one mains earth path. Discussions about earth loops etc can get complicated but having a single power point is the best first step.

Safety. I know electricians do not like an 'extension into an extension' I am not really sure why. If the primary extension is of the proper current rating and properly fused I can see no problem. I do agree it looks messy so maybe Sparks as a breed are OCD tidy?

All that said, DO buy quality products. The £3.99 six ways from Rock Bottom are not recommended. Look at CPC and others. The diss strips that get fitted to network cabinets are of excellent quality. If you feel qualified you can buy the strips and fit custom length cables. Avoid if you can strips that are touted as 'surge supressed and filtered' They rarely are needed in UK, do no good that I can see and can, in some circumstances, make ground noise worse.

Lastly, do not worry about loading and safety. Even a very big studio rig would not come close to the 13A limit. (that excludes things like lights, heaters or 2kW power amps!).

Just occurred. Power poles/pods are a neat solution.

:clap: :thumbup:

Oh! And welcome from me too! :)
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Re: Electrics in the project studio - Using extension leads

Postby Hugh Robjohns » Sat Jul 15, 2017 5:48 pm

BH12neil wrote:...but elsewhere on the net I've read that plugging extension leads into other extension leads is dangerous.

Lots of things in have the potential to be 'dangerous'. The trick is to gather knowledge and understanding to enable you to minimise or mitigate that danger. And with the best will in the world, the Internet isn't always the most reliable reference source! ;-)

As a general-purpose, arse-covering, rule, that standard advice is to avoid running one extension board from another. However, the reason is really only to avoid accidentally exceeding the current rating for the board's internal wiring and external cabling.

If you know the plug-board is built to a high standard, and you know the current demands of the intended installation, and allocate those loads to plug-boards appropriately, there is no risk. And in the case of a typical home studio, the total power loading -- and hence current demands -- will be way less than the roughly 3kW limit for a single wall socket / plug-board.

So, assuming you are using decent quality plug-boards with well-made socket contacts and switches, there really aren't any safety concerns at all. Obviously, though, the plug-boards should be fitted with the appropriate gauge of mains cable and fuses, but any reputable brand will be... (by law)

Also, don't ever use tarnished plugs! The oxide coating that forms on the plug pins over time increases the contact resistance, leading to potential overheating -- and you really don't want that. So it's worth unplugging everything at least once a year to check the state of the plugs, and clean them with deoxit d5 or similar.

There is an important difference between daisy-chaining and star-formations. In the daisy chain, you have board 1 plugged into the wall, and then board 2 plugged into board 1, board 3 into board 2, and so on (see below). If each board has four sockets then with three boards you would have a total of ten sockets available after they are daisy-chained together.

With the star formation, board 1 plugs into the wall, and then board 2 and board 3 both plug into board 1. This still gives you ten available sockets. However, the earth path from boards 2 and especially board 3 is very much shorter in the star formation, with everything being reference to the earth point in board 1 -- and that small detail can make a very significant difference when it comes to minimising ground loops.

In the daisy chain situation, board 3's earth reference is contaminated by currents flowing in boards 2 and 1...

plugboards.png


Finally, always plug the heaviest power-consuming devices into board 1, and in sockets as close to the exit cable as possible. This, again, helps to minimise contamination of the ground paths. We're talking here about big power amps, active speakers, chunky computers etc ...
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Re: Electrics in the project studio - Using extension leads

Postby BH12neil » Sat Jul 15, 2017 6:10 pm

Thanks everyone, your comments have put my mind at ease and I am now happy to move forward on the excellent advice given.

Cheers,

Neil
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Re: Electrics in the project studio - Using extension leads

Postby ef37a » Mon Jul 17, 2017 10:36 am

I am presently talking to a guy on another forum who is asking about the electrical systems he needs in a studio build in Amsterdam.

I have guessed it would be the French setup but any information would be handy.

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Re: Electrics in the project studio - Using extension leads

Postby Martin Walker » Mon Jul 17, 2017 6:35 pm

Hugh Robjohns wrote:Also, don't ever use tarnished plugs! The oxide coating that forms on the plug pins over time increases the contact resistance, leading to potential overheating -- and you really don't want that. So it's worth unplugging everything at least once a year to check the state of the plugs, and clean them with deoxit d5 or similar.

I echo this advice, and have heard improvements in low-level detail in my studio after my annual mains plug cleaning. The possible increase in contact resistance is as Hugh mentions is a possible precursor to overheating, but it also means that any ground loops in your studio may end up having increased current flow and therefore increased background noise.

Half an hour giving all your mains plug pins a quick rub with some wire wool followed by a small squirt of DeOxit D5 can make a noticeable difference in my experience :thumbup:

Oh, and welcome to the SOS Forums from me as well BH12neil! 8-)


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Re: Electrics in the project studio - Using extension leads

Postby Folderol » Mon Jul 17, 2017 7:54 pm

On the subject of plugs, there was a period when cheap ones from a country that (apparently) has a wall across it had live and neutral pins that were not properly finished, so that the socket contacts were riding on burrs instead of the faces of the pins (they were cut from long pre-formed bars of brass). I've not seen this for a long time - apart from anything else these pins must now have an insulated section.
However, it's worth checking any leads/adaptors that come from such a place, and ensuring that the pin faces are smooth and flat with a very slight rounding of the edges.
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Re: Electrics in the project studio - Using extension leads

Postby jagraphics » Tue Jul 18, 2017 9:09 am

One thing to remember is if you are using a coiled extension lead the current rating is a lot lower if the cable is could than if it is uncoiled. I have seen a heavy duty reel type extension lead only partially uncoiled to take the main supply to a lot of other gear.... after a while it started getting rather warm :-)

As the others have said get QUALITY extension leads. Always go for the higher current rated cables. A star configuration is best. Also Most important use appropriate fuses and have spare fuses.

Fuses do age and can blow at the most in opportune times. If when you replace the fuse it blows again FIND THE PROBLEM do not put in a higher rated fuse.

I know this is all blindingly obvious but it does bare repeating as some times people can do the stupidest things.... (see my wardrobe from the easily 70's..... :-)
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Re: Electrics in the project studio - Using extension leads

Postby Hugh Robjohns » Tue Jul 18, 2017 9:35 am

jagraphics wrote:One thing to remember is if you are using a coiled extension lead the current rating is a lot lower if the cable is could than if it is uncoiled. I have seen a heavy duty reel type extension lead only partially uncoiled to take the main supply to a lot of other gear.... after a while it started getting rather warm :-)

Absolutely! I've seen quite a few melted mains cable reels over the years.

The most entertaining one was at a recording of a Songs of Praise type programme many years ago. An inexperienced lighting sparks was asked to rig a big HMI light outside the church to illuminate the stained glass windows on one wall. Half way through the recording a member of the public came rushing in saying something was on fire outside!

Sure enough, the sparks had run mains to the HMI ballast unit from a big metal cable drum, but most of the cable was still wound on the drum. With the load from the HMI light being pretty high, the cable had overheated and the insulation melted, producing a lot of smoke.

Shortly after being alerted to the problem the light went out as the insulation failed and the mains cable shorted, tripping the breaker. Thankfully, the OB truck and everything else was on separate trips and remained powered up!

Needless to say, the whole mains reel was a right-off... and the junior sparks learned an important lesson.

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Re: Electrics in the project studio - Using extension leads

Postby Mike Stranks » Tue Jul 18, 2017 10:01 am

Ah yes! Melted cables reels...!

My best one was a 'have you got a spare extension cable?' in an open air situation where everyone's running off one genny. (No reason given as to why it was needed.)

Said 20m reel was left mainly coiled and used to power an urn and two kettles. Eventually it was a pile of gloop and, as in Hugh's case, got a short across live and neutral. That tripped-out the whole genny.

Of course, according to the powers-that-be it was my fault... 'twas ever thus! :D
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Re: Electrics in the project studio - Using extension leads

Postby ef37a » Tue Jul 18, 2017 10:33 am

Never lend nuffin' to nobody Mike!

If they don't already have it they probably don't know how to use it!

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Re: Electrics in the project studio - Using extension leads

Postby jagraphics » Tue Jul 18, 2017 12:58 pm

ef37a wrote:Never lend nuffin' to nobody Mike!
If they don't already have it they probably don't know how to use it!
Dave.

+100 (and + a few more if one one will lend them to me :lol: )

If they do have one but "forgot it" they will probably forget they forgot theirs and the one they have is yours and pack it in their bag when they go......

Or of course they may have one but "it just broke" so you can lend them one to try breaking when they repeat the process that broke the first one......

It's simply much better to be thought of as a Grumpy Bas*****d who doesn't lend kit and therefore who doesn't get asked than being "everyones friend" who lends kit and then looses friends (and kit) .
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Re: Electrics in the project studio - Using extension leads

Postby ef37a » Tue Jul 18, 2017 3:29 pm

And I WAS that Grumpy B***td when I had a workshop in a factory a few years ago!

People from sales would come asking for a battery drill (don't know HOW tf I was going to work without one!) and I would say "Give me a ten pound deposit and you can borrow one. They moaned a lot but none took up the offer.

In contrast the ladies on the shop floor would, on occasion, very politely ask to borrow a screwdriver. I would help THEM out because they would hunt me out from the other end of the factory, in their break time to give me the tool back!

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Re: Electrics in the project studio - Using extension leads

Postby Mike Stranks » Tue Jul 18, 2017 11:27 pm

As we're a-wandering off the topic...

... my favourite 'borrow' request is "Can I borrow some gaffa tape please?" Yup! Just stick all the bits back together at the end of the gig and give them back and that'll be fine! :D

I'm happy to lend DI boxes - or other hard-to-break kit - to people I know well. Similarly with cables... apart from that the only loans I do have me accompany them in a supervisory category. I call it 'damp hire'!
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Re: Electrics in the project studio - Using extension leads

Postby Sam Spoons » Thu Jul 20, 2017 11:49 pm

Or "moist hire" .........

I nearly lost a couple of LED PAR cans last Saturday. I was playing (supporting a Tribute band) but using their PA. The headliners were good but not sufficiently captivating and my back was playing up so, as I'd got my gear in the car, I sloped off early forgetting I'd loaned them a couple of lights.

The promoter (an absolutely sterling gent) rang me on the Sunday asking if the lights, bags and stands left at the venue were mine. I replied the lights were but not the other stuff (adding that 'd seen the DJ carrying some bags like he described into the venue). I went back when passing to collect the lights and they were nowhere to be seen. Today the Promoter found them locked in a backstage room (fair enough, they were, at least, safe from any light fingered 'Charlies') and dropped them off at my house asking, in passing, if a mic stand left there was mine? It was.... (senility check alert, I hadn't even realised it was missing) but TBF it did have a sticker with my name and mobile number on it (which said promoter, and the venue staff hadn't even thought to read......)..... It makes me wonder if my little lable printer (bought on Hugh's advice) was as good a purchase as I originally thought....... :beamup:
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Re: Electrics in the project studio - Using extension leads

Postby ef37a » Fri Jul 21, 2017 7:55 am

Getting back OT a bit.. (ok! ok! MY fault as well!)

Can The Team tell me if domestic ring main wiring is inferior for noise than a radial?
I can see that an old installation could have poor connections in such a way that the currents in the live and neutral conductors don't cancel but is there any real problem with a new installation?

Ring mains are peculiar to UK AFAIK and I think our overseas friends think they are the devils recipe for earth noise problems. Most of us are of course stuck with them.

Oh! And Sam? It will be senility when you start buying kit you already have!

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Re: Electrics in the project studio - Using extension leads

Postby Sam Spoons » Fri Jul 21, 2017 9:27 pm

I suspect myself of 'anility', I keep wanting to buy another of things I already have 'just in case'.......
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