to where do I connect the grounding terminal of an IEC connector? - Page 2 - diyAudio
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Old 29th November 2010, 02:03 PM   #11
AndrewT is offline AndrewT  Scotland
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the exposed conductive parts must be connected to the Safety Earth.
I should not have to repeat this but Mac is seriously in error.
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Old 29th November 2010, 02:14 PM   #12
Pano is offline Pano  United States
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Andrew - Please explain.

In the USA this is done for 2 reasons.
1) Over voltage (spike) protection
2) Fault protection. If the hot wire comes in contact with the chassis, the ground will trip the breaker quickly because neutral is tied to earth.

But if he has no exposed metal parts? What then?
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Old 29th November 2010, 02:26 PM   #13
AndrewT is offline AndrewT  Scotland
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Maybe he has no exposed conductive parts, but so far al he has given us is that he is using a plastics case/chassis.

If I come along and plug in an RCA interconnect, what do we have at the other end of that interconnect?

Two conductive parts: the Signal Flow and Signal Return.

Connect a pair of speaker cables. What is at the other end?
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Old 29th November 2010, 02:32 PM   #14
Boscoe is offline Boscoe  United Kingdom
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The ground in North America serves to protect you from over voltage spikes, lighting and such. If tied to a metal chassis, it can serve to trip the circuit breaker if there is a 120V short to the chassis.
In theory this is what's meant to happen only with you in the middle of the live and the earth! So when they trip when you make the circuit you don't die!

But tbh I don't know where to earth it in you case. You might not have to bother I have seen endless amount of audio equipment not earthed from big name manufacturers.
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Old 29th November 2010, 02:54 PM   #15
Pano is offline Pano  United States
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Good point Andrew.
But his low voltage audio section should be completely isolated by the power supply transformers. Thus the voltage on his RCA shield has no direct relation to earth, or to mains hot. That's how the mainstream ungrounded stuff works.

The problems come when it does get tied to earth. There may be one or more grounded devices in the system, or even the cable TV ground.
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Old 29th November 2010, 06:21 PM   #16
jitter is offline jitter  Netherlands
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After a discussion with some of you in another thread and reading Audio Component Grounding and Interconnection I decided to connect any mains powered DIY project I built or will build to PE (Protective Earth or Safety Earth). I even connected an appliance class II CD-player to PE after getting a jolt (see high potential on chassis CD-player). This means I have several pieces of equipment not only interconnected but to PE too. In theory this would mean groundloops. But I have not found any discernable ill effects of this (and I know very well what a groundloop can do as I had to solve a horrible one once). To quote David Davenport, author of the abovementioned article, "Loops aren’t bad – it depends on what is on the loop.". This turned out to be very true.

I have several commercial devices that are connected to PE. Some of them have circuit ground connected to PE and some do not. I think it depends on whether a fault in a transformer can cause mains voltage to be shorted to the secondary windings or not. If it cannot PE is not connected to circuit ground.

Last edited by jitter; 29th November 2010 at 06:31 PM.
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Old 29th November 2010, 07:33 PM   #17
DF96 is offline DF96  England
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If it possible for someone to touch a conductor in or around your circuit, either directly or indirectly, then that conductor must be referenced to ground so that it cannot become live. The exception is double-insulated equipment, but I understand that the regulations for that are difficult for a DIYer to achieve. So for almost all DIY the signal ground must connect somewhere directly to safety ground, and everywhere else it should connect indirectly to safety ground so that fuses still blow. Floating circuits are potentially dangerous, except where is it impossible to touch them.
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Old 29th November 2010, 08:48 PM   #18
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wait, so I have to connect signal ground (carrying the negative side of my phantom power supply) to safety ground?
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Old 29th November 2010, 08:53 PM   #19
Pano is offline Pano  United States
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DF96. Do you really see a hazard on the secondary side of a low voltage transformer?
Now I might see that in a big power amp with high voltage rails and high current. But in signal level devices? What do you think?

Signal ground can and often is connected to earth with no problems, so you can at least try it and see.
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Old 29th November 2010, 09:09 PM   #20
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Quote:
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Signal ground can and often is connected to earth with no problems, so you can at least try it and see.
Typically the only reason that's done is because the chassis is used as a shield. But since the chassis is plastic and doesn't provide any shielding, it's rather moot.

se
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