UK MAINS SUPPLY

[admin_exported]

THE UK MAINS

Many people take the Mains supply for granted. After all it works, it's reliable so whats to talk about?

I will try to explain.

Your Mains supply is not as straight forward as you might think.
The wiring from the Sub Station carries 230v Live (+ or - dependent on local load demands), and the 0v Neutral.

HUM INJECTION BY MAINS GROUNDING CURRENTS.
In many cases the "Mains Ground" is the Neutral conductor, which is ONLY grounded at the transformer Sub Station to your home, it serves many houses from connections tapped off its length.
There is substantial current flowing down the N+E conductor, so it's often 1 Volts rms or more ABOVE Earth.
In the internal house wiring, Neutral and Ground are ALWAYS separate with the Earth conduit grounded and Cross Bonded.
Now it is the voltage present on the Neutral and Earth conductors that give you the 'Noise Floor' which then effects your equipment.
If some ground current is unavoidable then the use of balanced inputs (or ground-cancel outputs- it is not necessary to use both) should give at least 40 dB of rejection at audio frequencies.

Custom made Mains cables help in this so that's why they improve the sound. However they do not totally eliminate the problem so that's why there's several more things that can be done.

 

[Anonymous]

Trevor, what are your references for this? I'm sufficiently interested to want to investigate further.

 

[Anonymous]

Tarquinh:Trevor, what are your references for this? I'm sufficiently interested to want to investigate further.

A good place to start is hear...

http://www.dself.dsl.pipex.com/ampins/groundloops/grndloop.htm

and then this.....

http://www.dself.dsl.pipex.com/ampins/balanced/balanced.htm

 

[Big Aura]

Trevor - can you explain (for the uneducated) how a custom mains cable helps - presumably you have a shoddy supply coming in, and you send that over a beautifully constructed cable - but the cable itself can't fix the underlying problem, can it?

I have one of those Tacima powerblocks - I presume that cleans it the supply, but do I then need a raft of custom mains cables between it any my kit? What can go wrong in the 60cm between the Tacima and the amp?

Cheers

Garry

 

[Anonymous]

Hi Garry

The object of the exercise is to get rid of the 'Noise Floor' before it gets into your equipment, for then the problem is made even worse.
So the 1st place to start is at the point where your Mains Meter Unit is and make the Earthing point there as good and clean as possible. Then check the Cross Bonding (water pipes) clean and tighten them.
So now you know that you have a excellent Earthing point in your house so the conduit will be running cleaner.
Now behind your units there is wires/cables running everywhere and they all are putting out / picking up RF pollution etc. Good cables will be shielded from this and some will even balance stray voltage on the Neutral line.
In an ideal world each piece of your system will be fed with 230v live, 0v Negative and 0v Earth going back to 1 good source.

Then it is just down to how well designed each component is to how well it performs!

 

[Anonymous]

You could well find after this that you are over the moon with how good your TV picture looks and your music sounds.

Knocks the itch of constantly upgrading on the head!

 

[margetti]

trevor79: So the 1st place to start is at the point where your Mains Meter Unit is and make the Earthing point there as good and clean as possible. Then check the Cross Bonding (water pipes) clean and tighten them.

Hi Trevor, maybe putting you on the spot a bit here, but is this safe for an unqualified electrician to do? I know it's Earth points we're talking about, but... Would it be prudent to turn the mains off before poking around, or is the OTT health & safety environment at work over-influencing me?

ÿ

 

[Anonymous]

Yes, of course if you are IN the consumer unit IT WANTS TO BE SWITCHED OFF.
At the meter unit the Earth bonded wire is well away from the live and Neutral wires and is completely separate to them.
Typically hasn't been touched since the house was built/or rewired so the EARTH grounding that your whole house relies on could be very poor!

If you are having any Mains faults (tripping fuses, shorting out, faulty wiring etc) get an electrician to look at it.

 

[margetti]

trevor79: At the meter unit the Earth bonded wire is well away from the live and Neutral wires and is completely separate to them.

ÿCheers - that was the bit - "completely separate" - that I was looking for! Yes, I know it was maybe a bit of an obvious question, but, well... 230V and all that!

 

[Anonymous]

I think Russ Andrews has written a booklet (or even a full book) on this subject, not sure if you can download anything .....?