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Old 12th May 2008, 11:22 PM   #31
gareth is offline gareth  Wales
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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.
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Old 13th May 2008, 12:28 AM   #32
studiot is offline studiot  United Kingdom
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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.
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Old 13th May 2008, 01:44 AM   #33
digi01 is offline digi01  China
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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

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Old 13th May 2008, 02:11 AM   #34
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Quote:
Originally posted by AndrewT
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?
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Old 13th May 2008, 04:17 AM   #35
gni is offline gni  United States
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Maybe like this:
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File Type: gif good_ground_6.gif (16.7 KB, 6214 views)
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Old 13th May 2008, 05:11 AM   #36
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Quote:
Originally posted by gni
Maybe like this:

GNI,

What happens in your diagram if either DC positive rail or negative rail is shorted to signal ground? Now there is a large DC voltage difference between amplifier and power supply chassis

I am considering this diagram:
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Old 13th May 2008, 08:39 AM   #37
AndrewT is offline AndrewT  Scotland
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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.
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Old 13th May 2008, 11:04 AM   #38
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Andrew,

Do you think my diagram is better or worse, with the revision of connecting Earth (through a wire in the cable) to the amplifier chassis instead of circuit ground to the amp chassis?
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Old 14th May 2008, 06:44 AM   #39
gni is offline gni  United States
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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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Old 14th May 2008, 09:37 AM   #40
AndrewT is offline AndrewT  Scotland
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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.
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