Mains Noise Suppression

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Spikes and pops, huh?
You can approach the problem from any number of directions. It may take a combination of things to get the noise under control. A couple of things occur to me off the top of my head:
--There have been at least two threads where we were talking about various strategies for filtering noise from the AC lines. You might want to look those up.
--Your system might be on the same circuit breaker as the noise-producing equipment. Try putting your system on an outlet that you know to be on a different circuit breaker. In particular, there's a trick that works for 120V AC lines--switch to an AC line that comes from the *other* side of the incoming 240V, as all the 120V lines on that side of the AC may be polluted by the hash.
--Indulge in a little fiddle factor on the power supply in your system. More capacitance in the main bank. Regulated rails. Small capacitors (.01-.1 uF) across the AC line before and/or after the power transformer.
Experiment a bit with some of the cheaper options, then proceed in whatever direction seems most promising.

Grey
 
Seeker

Grey is right in his response about minimising the pick-up of mains borne noise. However, you should also consider eradicating it at source as far as possible. The main culprits are switches and thermostats on things like fridges and central heating systems. The noise generated when the contacts make or break can be suppressed fairly easily if you can get access to the switch/'stat terminals, by wiring a contact suppressor across the contacts.

The contact suppressor can be purchased as a single device or can be made from a 120ohm resistor in series with a 0.1uF capacitor. If you make your own, ensure that the capacitor has a suitable voltage rating. The switch/'stat will be handling mains voltages so the capacitor must be rated for an rms voltage at least equal to your mains voltage (there are special types designed specifically for this purpose). Also ensure that all connections (eg capacitor to resistor) are insulated and cannot make inadvertant contact with any earthed metalwork. If in doubt, employ a qualified electrician to do the work for you.

In particularly difficult cases, a VDR (voltage dependant resistor) in parallel with the contact suppressor may be needed.

Geoff
 

tinitus

Ex-Moderator R.I.P.
2005-11-24 1:47 am
Hey, I need mains filters on my PC components

My hifi is picking up noise through mains
I have tried a "hifi" mains filter on my PC, and it helped
But that filter burned a while ago
Since then I have wound my PC mains wire on a small toroid core
It helps too, but not enough

I want to BUY some small simple filters
And not too expencive

Any suggestions which, and where (EU) ?

Or are there other options, like those to put on signal interconnects etc ?

Any experiences what really works here ?
 
If your system is solid state, the pops and cracks are probably from the broadband RF burst (from switch or relay opening or closing) getting rectified by some p-n junctions. While eliminating or mitigating the problem at its source might be best, you could also try a simple low-pass RC filter on each audio input, with a cutoff frequency of 200-300 kHz or so. To come up with the simple filters, see my two posts at http://www.diyaudio.com/forums/pass-labs/169382-f5-how-reduce-bandwidth-response.html#post2228277 . Also see point number three in my post at http://www.diyaudio.com/forums/chip...ival-hi-end-design-advice-34.html#post2245928 . If your power amplifier doesn't already have such filters, they should be installed in any case, probably as close to the first amplifier components as possible. If the bursts are getting in through the DC power rails, you might have to experiment with different decoupling/bypass capacitors, and possibly an additional small series resistance or a series inductance, depending on what stage is being affected most (small signal or large).
 
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jean-paul

Ex-Moderator
2002-09-20 7:20 am
Germany
We only have 2pin connectors here
Im not sure its even allowed to do what you suggest

No wonder that you have/had noise problems. What you do is not allowed and the suggestion to check the earth/ground connection is the right one ( except that is was called neutral by Brian which is not the correct name ). All computer power supplies are designed with a noise filter in them so no need for an extra filter. They do need safety earth/ground for filtering and safety. That is why all normal computer power supplies use the euro 3 pin connector with safety ground/earth and that is why a 3 pin euro cable with safety earth/ground contacts is supplied. Standard 3 pin connectors with safety ground should always be used in 3 pin "earthed" wall outlets. That way a connection from the computers safety ground/earth will be made to the safety ground/earth of the domestic installation that is properly "earthed" as described by law.

If you use any desktop computer unearthed you will not only have noise problems in for example your sound card but the computer will pollute the mains too because of its SMPS. And if you touch the metal case you will "feel electricity" or you will even experience a shock when touched with moist hands as it will carry half the mains voltage because of the resistors/caps in the mains filter connected from L and N to the (now not to safety ground connected) earth connection + case. Please check up how mains filters work, they do need an earth/ground connection to loose the noise to.

Only devices that have 2 pin connectors from the factory don't need safety earth/ground. These are nowadays so called "double insulated" devices. This system is often misunderstood in various european countries that insist every mains connected device should be "earthed" but this is not the case as the device is double insulated. The requirements can all be found on the web.

Some problems aren't problems but just severe user errors that start simple from an ignorant action but often cause problems later. Just connect the gear as it should be connected and it will be safe and the noise problem will be gone.
 
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I need mains filters on my PC components

My hifi is picking up noise through mains

We only have 2pin connectors here

connect the gear as it should be connected
All 2pin double insulated equipment must never be converted to use the third pin Protective Earth (PE) for extra safety nor filtering.

All 3pin equipment must use a 3pin mains connection with the third wire (PE) and must never be modified to remove that PE purpose.

It is always better to reduce interference at source, i.e. in the fridge/washing machine/"Hoover"/in the workshop.
 

tinitus

Ex-Moderator R.I.P.
2005-11-24 1:47 am
We have two kinds of voltage here
230V fore normal domestic electronic
Wall sockets are 3pin with earthing
Electronics are always with 2pin connectors without specicfic orientattion
400V fore professional workshops, with 5pin connectors and earthing
Fore stationary machines, or heavy portable machinery

Its true, lots of hifi does have a round 2pin connector with additional earthing on the side of the connectors
But the only approved wall socket here is 3pin
Yeah, a strange thing really
 

tinitus

Ex-Moderator R.I.P.
2005-11-24 1:47 am
All computer power supplies are designed with a noise filter in them so no need for an extra filter. They do need safety earth/ground for filtering and safety.

Might well be the problem on hand

Below is a picture of the 3pin wall socket used around here, and the only legal one

Strangely its now common that electronics use another kind of international 2pin mains cable
Used a lot fore hifi
Maybe better known as Schuko
My PC actually does have this kind of plug
As do the charger fore my portable PC

Matching wall socket would the blue one(picture)


So, I need to find some kind of adaptor, or cut the cable and mount other 3pin plug, or build a custom connector box

Man, no wonder theres so much noise on our mains :mad:
 

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jean-paul

Ex-Moderator
2002-09-20 7:20 am
Germany
Might well be the problem on hand

Below is a picture of the 3pin wall socket used around here, and the only legal one

Strangely its now common that electronics use another kind of international 2pin mains cable
Used a lot fore hifi
Maybe better known as Schuko
My PC actually does have this kind of plug
As do the charger fore my portable PC

Matching wall socket would the blue one(picture)


So, I need to find some kind of adaptor, or cut the cable and mount other 3pin plug, or build a custom connector box

Man, no wonder theres so much noise on our mains :mad:


Hi, if the left version (which I've never seen before) uses only the 2 pins then regulations in your country are plain unsafe. I see there is a third opening which appears to have a third pin to "earth" but since all standard cables in the EU use the outer contacts it still won't help much. As seen before a countries own standards will only end up in more costs and confusion since the majority uses the real standard types which of course will be cheaper as they're produced in much larger numbers. Besides that this is pretty unsafe as it is now, certainly if the organization that defines the standards in your country allow stuff to be imported with the Schuko plugs. In fact this seems such a serious safety problem that I would call that organization to reconsider safety regulations if I were a citizen like you living there. I am sure you get shocks when touching metal parts of computers in your country for the reasons I posted earlier. This can easily be measured with a DMM between case and PE/safety ground. There will be 115 V AC on the case if 230V is the voltage..

The right one is the standard Schuko that should be used in most European countries except for the UK with their ... eh, special plugs. When you use the right one (of course with the side contacts connected to PE/safety earth) you won't have problems.

Are you from one of the "newer" EU countries ? Just curious as the Schuko is standard for a very long time now. Although I normally would not advise to use stuff that is not allowed in this specific case I do advise to use the standard proven Schuko wall outlet with the side contacts. My motivation for this is that it would be way safer for you and your family. Best would be to remove the odd wall outlet and have it replaced for a Schuko one. While you are at it you could also change those in the rest of your house like the ones used at moist areas like the kitchen, the washing machine etc. Never use Schuko connectors that have side "earth" contacts without connecting those to safety ground/"earth"/PE !! So you have to have your electrician make sure the third pin in the now used outlets really is connected to PE.
 
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jean-paul

Ex-Moderator
2002-09-20 7:20 am
Germany
Type K (Danish standard)

As of 1 July 2008, wall outlets for type E (French 2-pin, female earth) are permitted for installations in Denmark [22]. This was done because no electrical equipment sold to private users is equipped with a type K plug, and to break the monopoly of Lauritz Knudsen — the only company making type K sockets and plugs.

Sockets for the Schuko F type will not be permitted. The reason is that a large number of currently used Danish plugs (coincidentally made by the afore mentioned Lauritz Knudsen monopoly) will jam when inserted into a Schuko socket. This may cause damage to the socket. It may also result in a bad connection of the pins, with resultant risk of overheating and fire. Broken type F sockets are often seen in German hotels visited by Danes.[citation needed] Many international travel adapter sets sold outside Denmark match type C CEE 7/16 (Europlug) and type E/F CEE 7/7 (Schuko-French hybrid) plugs which can readily be used in Denmark.


What a mess ! The webpage shows a lot of types used in Europe but nowadays the Schuko type F is very common (not only in Europe).
 
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Pano

Administrator
Paid Member
2004-10-07 6:05 am
Every country is different

Since we don't know the codes and practices in Tinitus' country, we don't know how his system is wired. He needs to find out what are the codes and standard practices there. His house may not comply, if it's old.

Having had my hands on wiring in the USA, Canada, Mexico, UK, France, Germany, Italy and Russia _ I can tell you that everyone does it differently. And everyone thinks their way is "best."

In the USA (and Canada, AFAIK) it's simple. Domestic power comes from the step down transformer on the street. The secondary of this transformer is 240V center tapped. The center tap is connected to earth at the transformer which is usually up on a pole. That earth connected center tap becomes what we call the "Bonded Neutral". It is at ground potential. It is connected to ground again at the service entrance to your house. The reason the neutral is bonded to ground is safety.

So we have 2 hot wires and one neutral. Between the 2 hots is 240 volts. Between either hot and neutral is 120V. Since neutral is bonded to ground, so either hot wire to ground is also 120V. Typically we use 1 hot and the neutral for our household devices. 2 hots will be used for the 240V devices such as watter heaters, clothes dryers, heat and air.

In the 1960s we added the ground wire. So now we have 3 wires. The ground wire mainly protects from voltage spikes, such as lightening strikes, but also acts as an additional drain to ground. Because current does flow in the neutral wire (it's 1/2 the circuit) it can sometimes be above ground potential. The ground wire normally carries no current, so "should" always be at ground potential. That makes it a nice drain for noise.

In other countries things are not done the same way. So you have to know what your countries codes and practices are. Consult a code book. Do not just ask, must people don't have a clue. Even some electricians don't. Once you know how things are supposed to be in you area, check to see if your house is really wired that way.
 

jean-paul

Ex-Moderator
2002-09-20 7:20 am
Germany
"Best" is not very impressive, "safe" and "standard" are. It is not a problem if a country chooses an own standard that they think is "best". If they do they should not allow foreign domestic appliances to be sold with "wrong" plugs that could cause harm to their people.

I have seen the same in countries with the british wall outlets and european Schuko type F cables on domestic appliances that are sold there. What will people do ? They use a ballpoint pen and force the Schuko plug in the british connector. It is matter of either joining international standards or an own "best" system with all imported appliances using the own "best" plug. If Schuko F type wall outlets are forbidden how-come computers can be sold with Schuko/IEC cables ?

The system panomaniac describes is the same here but here a 3 phase system (so 3 hot wires and a neutral) is used with ground. Between L and N there is 230V. Between the 3 phases (then called L1,L2 and L3) there is 400V. A special 3 phase CEE form connector is used in industrial environments for heavy equipment requiring 3 phase power. All supply wiring till 10 kV is in the ground and transformers are in special houses and not on poles as they earned the hard way that poles with transformers are a good recipe for black outs.
 
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Might well be the problem on hand

Below is a picture of the 3pin wall socket used around here, and the only legal one

Strangely its now common that electronics use another kind of international 2pin mains cable
Used a lot fore hifi
Maybe better known as Schuko
My PC actually does have this kind of plug
As do the charger fore my portable PC

Matching wall socket would the blue one(picture)


So, I need to find some kind of adaptor, or cut the cable and mount other 3pin plug, or build a custom connector box

Man, no wonder theres so much noise on our mains :mad:
I'm not shure if I understand you correctly. Schuko provides a threewire connection i.e. live, neutral and protective earth.
Two wire connections are used with safe insulated equipment only and come in europe with so called 'euro plugs' and cables.
Anyway, do you live in an EU country? I'm pretty shure that all electronic equipment sold in EU countries must comply with the national electrical safety and wiring standards. That includes the local used plugs.
So, if you haven't imported the things yourself or bought 'fell from a truck', you should ask your dealer for a proper mains cable or at least a suitable adaptor.
regards
 
All supply wiring till 10 kV is in the ground and transformers are in special houses and not on poles as they earned the hard way that poles with transformers are a good recipe for black outs.

And we learned here that underground equipment is frequently underwater, therefore is a good recipe for black outs. As you say, there is no 'best'.
 
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