you should never!!! connect the ground to neutral.... as far as in norway, its against the law. ref. to NEK 400. 2012
floric: (excuse my english)
neutral is tied to ground at the distributor
you have a separate ground in your home
there is a differential circuit breaker in your house, it measures the difference in intensity between live and neutral if it exceed 30mA (here for modern house, 600mA in old house) it will trip if there is a fault maybe through a human connected to ground or a casing to your home ground (should be less than 60 ohms) so a human should get less than 2 volts wich is harmless.
if you connect your amp between live and ground the circuit breaker will trip... or your home wiring is not safe, and I suggest you correct it!!!!
one thing you can do is to connect your amp ground to a nearby radiator or water pipe (leaving your psu/xformer connected to live and neutral) these pipes are often quite well connected to ground but if you have a fault in your amp, no differential circuit breaker, and an isolated (from ground) pipework you could "distribute" mains voltage around through the pipes...
... this is what I think I know... and what I do here!
neutral is tied to ground at the distributor
you have a separate ground in your home
there is a differential circuit breaker in your house, it measures the difference in intensity between live and neutral if it exceed 30mA (here for modern house, 600mA in old house) it will trip if there is a fault maybe through a human connected to ground or a casing to your home ground (should be less than 60 ohms) so a human should get less than 2 volts wich is harmless.
if you connect your amp between live and ground the circuit breaker will trip... or your home wiring is not safe, and I suggest you correct it!!!!
one thing you can do is to connect your amp ground to a nearby radiator or water pipe (leaving your psu/xformer connected to live and neutral) these pipes are often quite well connected to ground but if you have a fault in your amp, no differential circuit breaker, and an isolated (from ground) pipework you could "distribute" mains voltage around through the pipes...
... this is what I think I know... and what I do here!
In Germany professionals are not allowed to implement new installstions like that.
Hello Paulv,
... my electrical english isn't very good ...
No in the installations here there is no ground provided by the ditributor. There are three phases "live" and a neutral. The ground is suppilied by a earthing point (a pole in the earth) that belongs to my house. At the entrance of the neutral line into the house, the ground and the neutral are connected, the supply pipes of the heating, the gas, the water etc. (all metal parts). After that point there is the electicity meter of the supplier and then the differential circuit breaker after that the three "live phases" are split to supply seperate "chains". In my case there are two circuit breakers, one for the new cabeling (with supplied gorund, neutral and live to every outlet, light etc.) ond one for the old cabeling that still supplies some rooms (only neutral and live, "ground" is supplied by a connection in every outlet, light installation etc.).
I did ths installation myself and it was proven and approved by a professional electcian and by the supplier. both cicuit breaker break at a differential current of 30mA (and they work both). As far as I know this kind of installation is common in Germany. Since the 70s, only the "the wire" installation is allowed for new installations (done by a pofessional). The old kind of "two wire" installation is still accepted for existing installations.
I thought these two types of installation are common, at least in europe. At least in italy I already saw similar installations (of both types). If there are differen prctices in other countries, please excuse me.
In the text above, I omitted the fuses there are fuses of course.
Now back to the topic:
The problem is, that normally you have neutral and live on the outlet but you can't be sure, in which direction the plug is inserted. So you don't know, which of the two cables is neutral. As long as you supply the transformer with the voltage between those two cables, that does not matter, because after the transformer, you you have a voltage between the two ends of the secondary winding, no neutral and live, just differential. After a rectifier you still have a differential DC voltage (a "+" and a "-" for a single voltage). If you connect two devices together e.g. by a signal line, you need ot tie the "-" of the two together in order to get a defined potential, this is "grounding" if you don't do it, either the singal (a voltage) won't be defined (you may even hear music) or the grounding will be done via the signal wire which normaly causes hum.
So we need a wire that connects the "virtual grounds" together. You can't take the neutral wire, because you don't know which one it is. In many cases it is done via the ground wire from whch you know which it is- you may look at a lot of power supply schematics that do it exactly this way.
If you don't have a ground wire, you can take the neutral wire as ground (for the ps) but you have to seperate this wire from the neutral at a piont where you know for sure which one ist the neutral and were you can be sure that no one will change the connection. This can be done in the outlet.
With this practice your gear will work. But normally the case is connected to gorund and in the case of a fault, the supply voltage may be connected to the case if you use this practice. This may be lethal! So you need another way to provide your savety and that's the reason why you need a differential circuit breaker.
Sorry if my wording and my argumentation is not exact in terms of engineering, I'm a scientist not an engineer and it's hard to express ths without a drawing at hand. I just wanted to describe, what could be the problem of the f5 sounding bad with no ground connected. I already fixed a similar case for a friend of mine. Not sure, if this problem can be fixed like this too.
Best regards
hello Floric
what a long explanation! I learned something:
the difference with here in france is that you connect neutral to earth BEFORE the meter, circuit breaker etc, which in a way is a good thing (lower resistance of the earth), and from there you split again phase, neutral (those are going through the circuit breaker) plus ground wire that runs direct.
Even if you are sure which is the neutral you should never connect it to the case, in the event of a fault (live wire touching the case) the circuit breaker would not trip.
back to hifi:
many systems have only two wire connection: neutral and live
the common ground between appliances (CD preamp, amp, tv) is done through signal (audio) cables and the whole system is left "floating" , no reference to earth, which is OK with good transformers and isolation, if you had two ground connections in each appliance (the socket ground plus the signal ground) you would have ground loops which generate hum.
It can be usefull to have your system referenced to ground but then connect only one appliance to your socket ground (NOT THE NEUTRAL), and do it on the small signal appliance (cd, turntable).
... balanced connection have a high immunity to ground loops, noise and hum...
lastly: are we off topic????
cheers
Paul
what a long explanation! I learned something:
the difference with here in france is that you connect neutral to earth BEFORE the meter, circuit breaker etc, which in a way is a good thing (lower resistance of the earth), and from there you split again phase, neutral (those are going through the circuit breaker) plus ground wire that runs direct.
Even if you are sure which is the neutral you should never connect it to the case, in the event of a fault (live wire touching the case) the circuit breaker would not trip.
back to hifi:
many systems have only two wire connection: neutral and live
the common ground between appliances (CD preamp, amp, tv) is done through signal (audio) cables and the whole system is left "floating" , no reference to earth, which is OK with good transformers and isolation, if you had two ground connections in each appliance (the socket ground plus the signal ground) you would have ground loops which generate hum.
It can be usefull to have your system referenced to ground but then connect only one appliance to your socket ground (NOT THE NEUTRAL), and do it on the small signal appliance (cd, turntable).
... balanced connection have a high immunity to ground loops, noise and hum...
lastly: are we off topic????
cheers
Paul
Surely this can't be true.
In Europe (we have the harmonised power supply) the mains power is fed in via the Live and returns via the Neutral.
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I've had a debate with a friend about the difference between US and European power. He thinks there is something different about the phase and says a 220v motor will not work on both systems. To me, the power is basically the same except for a center tap which is used as the neutral in the US.
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You are right, the circuit breaker would trip only if someone touches the case. If it is sensible enough (30mA e.g.), this is not very pleasant but far from lethal. In most cases the fuse will blow because of the short circuit.
Hello Paul,
to get even more back to the topic. Look into http://www.firstwatt.com/pdf/prod_f5_man.pdf page 18. The gorund of the PS is connected to ground via a thermistor (which acts as a ground loop breaker to avoid hum and could be left out). You may find hundreds of examples construced like that sometimes with ground loop breaker or ground loop resistance, sometimes without.
I think an F5 would not work correctly without even if other devices do because they are constructed different. There might be cases where a setup like this will work, but not in every case.
But with this construction you "earn" an additional risk: In the case of a fault in the transformer you may get line voltage at the case (which is connected to ground too).
To find a solution to the F5 problem above: Whi not connect the case of the computer so the case of the F5?
Regards
Flo
I would star Earth directly to each of any metallic enclosures, not "chainwire" it for safety reasons. In F5 leave the audio ground float from chassis with only a CL60 from audio star ground to chassis. Hope this helps,
Best,
nAr
over here youcan turn the plug 180 degree and plug it back in. so no live/netrual.
It doesn't mean you don't have live/neutral. We can do it too here in France and there is indeed live / neutral. Mains is asymetric by nature, i.e. one can measure 230V between Live and Neutral, but also Live and Earth. But between Neutral and Earth you don't have anything significant in general.
Do bear in mind that the power is distributed in 3 phases (triphase) before big district xformer. Once here all loads (phases) are power-balanced against it, and Neutral is a special return path to the big xfo they assign you. So between phases you would have 380V, perhaps your neighbour has a different phase from xfo than you
but perhaps the same. Between Phase and Neutral they give you you have the 230V ... Best,
nAr
i would suggest getting one of the neon bulb pocket line-testers. once you've wired up the amp make sure that the switched side is the "hot".
there's a "differential scope probe" video with folks from Nat Semi (Bob Pease RIP among them) and a Tektronix sales/tech rep on youtube -- one of the guys said to the Tek technical rep "the first thing i do when i get a new scope is cut off the ground plug". Can't see it on the video, but i am sure that the Tektronix guy's eyes were rolling around in the back of his head.
and 30mA is more than enough to kill ya.
there's a "differential scope probe" video with folks from Nat Semi (Bob Pease RIP among them) and a Tektronix sales/tech rep on youtube -- one of the guys said to the Tek technical rep "the first thing i do when i get a new scope is cut off the ground plug". Can't see it on the video, but i am sure that the Tektronix guy's eyes were rolling around in the back of his head.
and 30mA is more than enough to kill ya.
That's right but the lethality (right word?) depends on the time the current flows through the body. Normal differential circuit breakers, at least the ones used in households, have switching times from 20ms to 40ms. The 30mA can kill you if they flow for more than 1s. For 20ms you would survive 500mA.
But I would not try it, better to avoid accidents like that.