| arold19 |
Hello, I have a bizarre trouble...
I have a gainclone at home and it work very well on my speaker at home. This week, I tried my gainclone with my friend system and it make a loud hum.....
I don't undertand, maybe because de "cheap" dvd player of my frind doesn't have ground ??
Maybe the speakers are two sentisive ???
With nothing at the input, it make no noise, when I plug the dvd player, the noise apper.
Do you know the problem ?? |
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| GregGC |
Connect the two (amp and DVD) in the same power outlet and see if the hum still there. Something to do with the GND loops.
Is the DVD connected to a TV? Where is the TV connected to? Disconnect the TV from the DVD player.
/Greg. |
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| arold19 |
Yes, the video output of the DVD player is in the TV, and the audio output is in the gainclone.
This can cause a problem ??? |
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| arold19 |
This was the problem! The noise leave when I disconnect the video cable.
But, How I can listen a movie??? If a plug the video cable, I have a big hum in the speakers and if I don'T plug the video cable, I don'T have image !!!!!!
The TV doesn't have any gound. The power cord of the TV have only 2 pin.
How can I repear this problem ???
Thank you !!! |
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| dalbjerg |
The TV doesn't have any gound. The power cord of the TV have only 2 pin
That's right but the TV is grounded thru the antenna cable. You can by an isolation trafo to either the antenna cable ore the audio (2) |
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| leadbelly |
If you do a search on "ground loop" you will come across many suggestions and examples of fixes. You will possibly need to buy or make yourself an isolation transformer for the cable connection.
AC devices are grounded even through a 2 pin plug. That's why it's important to not mix white wires and black wires. |
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| leadbelly |
| quote: | Originally posted by dalbjerg
[BThat's right but the TV is grounded thru the antenna cable. [/B] |
No, that's misleading. The TV is grounded through the 2 pin plug AND the video cable. If it wasn't, there would be no loop. It's why the white wire is white and the black wire is black (or blue and brown overseas). |
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| Frank Berry |
Disconnect the TV antenna. Does the hum go away?
I have been able to break the ground loop in cases such as this by opening the shield of the TV antenna cable and connecting a couple of 100 pf capacitors across the break. This breaks the loop at audio frequencies but permits RF to pass. |
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| dalbjerg |
The TV is grounded through the 2 pin plug
I’m sorry too tell you that in the whole EU no TV is connected galvanic to ground thru the 2 AC wires. That will mean that you could have 230Vac (110V ) on the chassis. That would mean that you would actually touch the Powerline on the antenna plug, scart and SVHS if you turn your power plug the “wrong” way. The only connection to the Powerline came from the condensators in the net filter. In EU the CE marking tell that the only wire that most be grounded should be marked yellow/green, and must not draw any current <10mA. |
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| leadbelly |
| Thanks for clearing that up. I had been under the impression that Europe had adopted polarized plugs as North America has. |
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| arold19 |
It's true, when I get off the calbe antenna of the TV, the noise gone.
So, thank you very much for the help, I will do or buy a filter..
Thank you !!! |
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| macboy |
| quote: | | Thanks for clearing that up. I had been under the impression that Europe had adopted polarized plugs as North America has. |
You are mistaken about north american wiring. On two pin plugs, one is the "hot" and the other is the "neutral". Neither is ground. Only 3 pin plugs have a ground, and as dalbjerg said, it must never carry a significant current. |
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| peranders |
| quote: | Originally posted by dalbjerg
The TV is grounded through the 2 pin plug
I’m sorry too tell you that in the whole EU no TV is connected galvanic to ground thru the 2 AC wires. That will mean that you could have 230Vac (110V ) on the chassis.... |
I must correct you a little here or make it clearer. Older TV has "hot" chassis via a fullwave rectifier bridge.
IF the TV has some sort of audio output, like headphones or speaker, the TV has:
1 An output transformer, older TV's
2 Cool chassis (not hot)
No TV has "hot" audio output, not very safe :dead: |
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| leadbelly |
| quote: | Originally posted by macboy
You are mistaken about north american wiring. On two pin plugs, one is the "hot" and the other is the "neutral". Neither is ground. Only 3 pin plugs have a ground, and as dalbjerg said, it must never carry a significant current. |
No, I'm not. What makes the neutral "neutral" is that it is attached to ground in the circuit panel, hence it can be part of a ground loop. |
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| UrSv |
| quote: | Originally posted by leadbelly
Thanks for clearing that up. I had been under the impression that Europe had adopted polarized plugs as North America has. |
Some parts do have somewhat polarized plugs like France who has a plug (Schuko style) which can only be inserted one way, GB with their dinosaur (in the most positive sense) plug or Switzerland which have fully polarized plugs. |
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| arold19 |
The TV is new.
What I want to say, it is that the TV is not grounded.
The "negative" of the RCA plug is connect with the "negative" of the coaxial plug of the "wall" because they are together inside the TV.....
The noise came from the antenna cable. |
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| peranders |
| quote: | Originally posted by arold19
The noise came from the antenna cable. |
Unplug the antenna and measure the ground of the antenna. Maybe someone has defect TV connected. I had this problem where I lived before. The ground of the antenna was at 230 V potential. When I connected my stereo to the headphone jack. Guess what happened?:yikes:
The TDA2002 exploded! and the feedback resistors went to heaven :wchair: |
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| ir |
| quote: | Originally posted by UrSv
Some parts do have somewhat polarized plugs like France who has a plug (Schuko style) which can only be inserted one way, GB with their dinosaur (in the most positive sense) plug or Switzerland which have fully polarized plugs. |
apparently the New Zealand/Australian plugs are the safest in the world. the ground pin is always longer then the other two as well so it makes contact first
this is all a bit off topic anyways |
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| macboy |
| quote: | You are mistaken about north american wiring. On two pin plugs, one is the "hot" and the other is the "neutral". Neither is ground. Only 3 pin plugs have a ground, and as dalbjerg said, it must never carry a significant current.
No, I'm not. What makes the neutral "neutral" is that it is attached to ground in the circuit panel, hence it can be part of a ground loop.
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I'm afraid that you are.
The neutral is connected to ground at some point (nowhere near your breaker panel or your house!). However, no electrical device should ever consider the neutral to be ground, and it along with the hot wire must be isolated from the case or anything else that a person may come into contact with. Currents flowing through the Neutral wire will create a potential difference (voltage) between it and ground. This isolation (usually galvanic isolation, i.e. transformer) also completely eliminates the possibility of a ground loop via the neutral wire. |
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| leadbelly |
| quote: | Originally posted by macboy
I'm afraid that you are.
The neutral is connected to ground at some point (nowhere near your breaker panel or your house!). |
The neutral actually originates in your circuit panel. The feed from the utility is 240V single phase. There is no neutral coming from your utilities service. The neutral is created by grounding inside your panel. Open up your panel if you do not believe me. |
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| janneman |
Well, I don't know which country you live in, but that practise (grounding the neutral in your distrib box) can get you arrested for criminal neglect in The Netherlands, and indeed most of Europe. We get 3 wires from the power company, phase, neutral and ground (and the other phases, but most of the times these are not used in house installlations). Are you sure your panel wasn't put in by some unqualified moonlighter trying to skimp a few bucks?
Jan Didden |
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| leadbelly |
| quote: | Originally posted by janneman
Well, I don't know which country you live in, but that practise (grounding the neutral in your distrib box) can get you arrested for criminal neglect in The Netherlands, and indeed most of Europe. We get 3 wires from the power company, phase, neutral and ground (and the other phases, but most of the times these are not used in house installlations). Are you sure your panel wasn't put in by some unqualified moonlighter trying to skimp a few bucks?
Jan Didden |
You may not have heard, but mains is 120VAC over here :)
Arguing this is just brutal. Just do a net search if you don't believe me!
http://www.electricalknowledge.com/...asp?TOPIC_ID=50 |
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| dalbjerg |
Sorry leadbelly, some one has fumbled on your electrical system.
According to your national organ Canadian Electrical Code (C.E.C.) and ESA you must have 3 wires in a wall outlet with 3 pins.
See this link http://www.electrical-online.com/ho...s/Grounding.htm
"If you live in an older home (pre 1960's), you may have "polarized", rather than grounded receptacles. Polarized receptacles operate on a 2-wire vs. a 3-wire system. A polarized receptacle visibly differs from a grounded receptacle as they are two, rather than three-pronged. Important to note that you cannot change a polarized receptacle to a 3-prong grounded receptacle without either grounding the outlet properly, or using a GFCI receptacle. (Check local electrical authority and codes.)
Some one (Sweden) said that old TV’s are connected at the chassis. That’s right but they all have a trafo in their antenna circuit.
This topic can seem to be irregular, but here are so many opinions and standards in line power writing. I have been a sound engineer for several years, and often there are problems with musician/PA equipment from other countries. (I’m sorry to say that the Danish system is bad, but wee have no ground in our normal outlet, only in wet rooms). |
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| runebivrin |
To the best of my knowledge ground and neutral are connected at the fuse box in Sweden. In fact, that's where protective ground comes into existence. Then again, we almost always use all three phases within a household for even load distribution and less impact of single phase failure. Nowehere have I've seen a separate ground connector from the electricity company.
It's important to understand what the protective ground is for: to ensure that fuses blow if a live wire comes in contact with the metal case of an appliance.
Ground fault protection is an entirely different beast, which relies on measuring the difference in current between live and neutral. More than approximately 10mA difference, and the breaker trips, as it means current is escaping on an alternate route.
That said, it's a sound practice to make no assumptions what so ever on what wire is which in an outlet. Your appliance should work equally well either way, if the PSU is well built.
I'm fully aware different countries have different standards, but I'm pretty sure all of EU use similar wiring standards, and when you think about it, running the ground conductor all the way to the power company makes very little sense, as it would only increase the risk of dangerous failure along the way.
Rune Bivrin |
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| leadbelly |
| quote: | Originally posted by dalbjerg
Sorry leadbelly, some one has fumbled on your electrical system. |
I hate threads like this, having to outshout the dunderheads so someone in the future doing a search will not be mislead. Don't worry about baiting me, I will not post in this thread again. So I will shut up and just post links to what others say:
http://www.faqs.org/faqs/electrical...section-17.html
"Since the white wire is connected to neutral and the grounding conductor inside the panel, the proper term is "grounded conductor"."
http://www.faqs.org/faqs/electrical...section-15.html
"There are logically four wires involved with supplying the main panel with power. Three of them will come from the utility pole, and a fourth (bare) wire comes from elsewhere."
http://www.faqs.org/faqs/electrical...section-32.html
"Nowadays, many two-prong devices have one prong wider than the other. This is so that the device could rely (not guaranteed!) on one specific wire being neutral, and the other hot. This is particularly advantageous in light fixtures, where the the shell should neutral (safety), or other devices which want to have an approximate ground reference (ie: some radios)." |
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