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Old 11th May 2008, 09:15 PM   #21
forr is offline forr  France
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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.
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Old 11th May 2008, 09:35 PM   #22
tsz is offline tsz  Sweden
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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?
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Old 12th May 2008, 07:13 AM   #23
digi01 is offline digi01  China
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Quote:
Originally posted by fluckscapacitor



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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Old 12th May 2008, 07:24 AM   #24
digi01 is offline digi01  China
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Quote:
Originally posted by tsz
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
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Old 12th May 2008, 02:48 PM   #25
AndrewT is offline AndrewT  Scotland
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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.
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Old 12th May 2008, 03:23 PM   #26
gni is offline gni  United States
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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. . .

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Old 12th May 2008, 08:15 PM   #27
gareth is offline gareth  Wales
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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
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Old 12th May 2008, 09:28 PM   #28
gareth is offline gareth  Wales
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Perhaps another thread could be started that explains the differences??

Gareth
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Old 12th May 2008, 09:40 PM   #29
studiot is offline studiot  United Kingdom
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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

Quote:

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.
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Old 12th May 2008, 09:54 PM   #30
AndrewT is offline AndrewT  Scotland
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Quote:
The exposed conductive parts must be permanently connected to the Safety Earth.
Quote:
Originally posted by studiot
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.
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