understanding star grounding

Star grounding is a technique which often helps a lot but it is not per se a concept. And ground loops are not necessarily evil. For example, fig post #4 rarely gives hum if the shields are very close, just as they are in most circumstances when using twin cables with RCA connectors at both ends.
 
fluckscapacitor said:



If this grounding scheme is used, but the power supply is in a separate chassis (6 foot cable between the two), should the break resistor be put in the amplifier or power supply chassis?

here you go:)
if you do not like break resistor you can use the other kinds of disconnect network or connect the power g to the chassis.

Zang
 

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tsz said:
In the connection of post #5 the supply currents to channel 2 and 3 combined with the resistance in the ground wires to channel 1 should give rise to (or am I wrong?) a voltage on the inputs 2 and 3 (referred to their grounds). Will this be significant?


the start point of #5 is basis on you do not use the other ground bar.you have to connect all ground wires to a reference 0V point(circuit GND).

Zang
 
Hi,
all these recent diagrams omit the Safety Earth.
These will completely mislead any newbie and even more experienced builders, into thinking that what is on the diagram is sufficient.

I suggest that all these diagrams that have a dangerous layout, by omitting the Safety Earth, be removed from this thread, before someone gets killed.
 
I admit that the diagrams do omit what type of connection there
is to the AC mains.

If each independent power supply is a double insulated switch-mode,
there there would be no connection to earth ground and the case
could be plastic. That is how it would work in the USA where
we use 120VAC mains.

Three prong connection would require special considerations that
AndrewT and others have outlined in many threads. . .probably
save my life and other in the process. . .
 
People really need to understand the diffefrence between Double Insulated (Class 2) equipment and 'Safety Earth' type equipment(Class 3).

The differences are very, very, major and not to be taken lightly. As has been mentioned by others the differences and misinterpretation could kill if not understood.

Electricity kills people. Under the right conditions 30mA or 0.03A is enough to cause defribilation or death.

Gareth
 
The use of an earth lift resistor can indeed be a dangerous practice if carried out inappropriately.

The technique is sometimes used in stage setups to avoid unwanted hum or other interference/coupling.

It has also lead to some unfortunate accidents and even fatalities in these circumstances so its use its best avoided.

However the following is too sweeping a statement

The exposed conductive parts must be permanently connected to the Safety Earth.


You are surely not suggesting that both the tip and ring of a mains adapter jack plug should be earthed? That would short the supply!
Both tip and ring are exposed metal parts that can be grasped by user and are also connected to the circuit.


Any circuit designer will tell you that circuits soon become so complex that avoiding earth loops is impossible.

In fact the old maths question of connecting three supplies to three houses on a flat sheet of paper proves this topologically.

The real trick is to avoid have large (return) currents flowing in the same segment as that used for input grounds.
 
The exposed conductive parts must be permanently connected to the Safety Earth.
studiot said:
However the following is too sweeping a statement
..........
You are surely not suggesting that both the tip and ring of a mains adapter jack plug should be earthed? That would short the supply!
Both tip and ring are exposed metal parts that can be grasped by user and are also connected to the circuit.
If the equipment is NOT compliant with the double insulated standard then it must meet that Safety Earth condition.
It is not too sweeping. It's how they are built by competent manufacturers and we as DIYers are expected to meet at least the same safety standards.
If you knowingly don't and someone gets injured/killed or property damaged then the criminal/civil proceedings may push the point home.
 
In respect of extraneous conductive parts then only the casework needs to be 'Bonded' to the main supply earth, except when Double Insulated (Class 2) equipment is used.

Please do not give out the wrong information with regards to Electrical Supply or somenone is going to get seriously hurt if not killed.

If you need diagrammatic evidence this can be provided.

Bonding every extraneous conductive part is practically (in respect of Audio projects) un-achievable.

Thanks
Gareth

PS..I really do think that a thread needs to be started to explain the differences between Class2 and 3 before someone gets hurt and never does a DIY project again. This is serious.
 
Some devices are not (double)insulated they are isolated .
Mains adapter power supplies are one such. They are, of course , designed to produce a 'live' voltage on an external metal part.

The power supplies, with or without transformer, are capable of breaking down internally so that it is possiible for the line voltage to transfer to the external jack.

It's just not possible to double or even single insulate something which is designed to draw power form the mains and present it at a metal terminal.

You can insulate the mains connections and isolate the input and output circuitry, but you cannot guarantee that there will never be crossover.
 
hi all,
this thread is talking about signal grounding.
for more information of safety.you will google EC earth.
i recommend IEC 60950, http://www.i-spec.com/IEC_60950/iec_60950.html suggestion
diyers should first understand IEC standard before they start to make things:)

i have to say all diagrams does not omit the Safety Earth.the break resistor or disconnection network are work on the amplification circuit duty.

have you see this?Post #11
for three prong connection,you should connect the Safety Earth(E) to the chassis of cause.

Zang
 
AndrewT said:
Hi,
all these recent diagrams omit the Safety Earth.
These will completely mislead any newbie and even more experienced builders, into thinking that what is on the diagram is sufficient.

I suggest that all these diagrams that have a dangerous layout, by omitting the Safety Earth, be removed from this thread, before someone gets killed.


Why not just modify his diagram to reflect the safeway to implement his suggestions/ideas?
 
Hi Gni,
can you add the label "Safety Earth" to your diagram.

Can you add a note stating " the ground connection pin in the umbilical cord must contact first and disconnect last to ensure the Safety Earth is in place in the amplifier before the PSU power poles connect".
BTW,
XLR plugs and sockets are designed to achieve exactly this.
Similarly UK style square pin plugs achieve the same requirement.

Your diagram shows, excellently, just how the RCA input barrels and the speaker terminals are Safety Earthed via the PSU. That complies with the rules that Gareth insists are impractical/impossible to meet.
 
I hope this fixes some problems of previous diagrams. . .such an
important issue. . . .some sort of standardized diagram for all
instances is needed. . . .

studiot made a good point I think by stating there is a real difference
between double insulated and isolated!

More research. . .great links by all. .

Seems there must be four conductors to allow for a safety earth connection
to both boxes. . .then a power supply return (ground). . .

The new diagram hopefully addresses both AndrewT and fluckscapacitor concerns. . .

10:30 PM California time. . .too late for me. . .I'll work more tomorrow.
 

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Hi Gni,
your last diagram addresses all the issues I had. Excellent.

Does anyone else see any problem?

Do we need a dedicated fourth conductor between the chassis?
Can the audio ground lead going to the disconnecting network do the duty of carrying fault current back to the PSU?

If we get agreement on your diagram, then I suggest it becomes the Wiki standard for two box amp/PSU.

BTW,
your diagram can become a single box amp/PSU with just the removal of the extra box and the short length of surplus Earthing wire.
How about posting that once we see others' comments.