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Headphone amp case and AC earth and safety

Music1969

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Hello all

I did a continuity test between the AC earth pin of my SMSL SP400 headphone amp and the rear silver screws you can see in the photo attached (photo is from @amirm's review, my iPhone battery was flat a the time).

And the continuity test beeps. Just on these silver screws.

What does this mean in terms of safety?

In the context of some kind of electrical fault, is this anything to be worried about? Or normal stuff?

1629276594907.png


SP400 PCB.png
 

solderdude

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This means the enclosure is connected to safety ground, as it should.
Is there continuity between pin 1 (XLR) and the screws ?
 

restorer-john

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It means your device has an effective chassis earth. Which is a good thing.

It means that you are considerably less likely to recieve a fatal electric shock should there be a catastrophic internal failure where full mains potential became applied to the chassis. Your ELCB/RCD/Safety switch would trip and/or your main fuse panel breaker before you took a hit.

That's all.
 
OP
M

Music1969

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This means the enclosure is connected to safety ground, as it should.
Is there continuity between pin 1 (XLR) and the screws ?

Thanks !

I will test this later but I did test continuity between Pin 1 XLR and AC earth pin and it beeped.

So so since screws + AC earth also beeped, I would guess that XLR and screws would also beep.

i.e. all 3 continuous

Would that be a good thing?
 

solderdude

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Yep, that would be a normal condition.
 

EB1000

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I'd avoid any earth grounded audio gear. This is a bad design, done only to satisfy the audio-fools community. Audio gear should have double isolation for safety. You don't see AV receivers with 3 prong power cords, which is why ground loops in AV receivers are very rare.
 

Atanasi

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I'd avoid any earth grounded audio gear. This is a bad design, done only to satisfy the audio-fools community. Audio gear should have double isolation for safety. You don't see AV receivers with 3 prong power cords, which is why ground loops in AV receivers are very rare.
Earth grounded is still the best practice for balanced connections. AVRs usually have only unbalanced connections, where isolated makes sense.
 

restorer-john

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I'd avoid any earth grounded audio gear. This is a bad design, done only to satisfy the audio-fools community. Audio gear should have double isolation for safety. You don't see AV receivers with 3 prong power cords, which is why ground loops in AV receivers are very rare.

Seriously, that is position utterly deluded. :facepalm:

Hardly "bad design", it is good design. Safe design.

And you say "double isolation". You mean double insulation. And, it is not inherently safer from a safety perspective, especially when most implementations are faulty, flawed, or simply unsafe in the first place.
 

EB1000

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Seriously, that is position utterly deluded. :facepalm:

Hardly "bad design", it is good design. Safe design.

And you say "double isolation". You mean double insulation. And, it is not inherently safer from a safety perspective, especially when most implementations are faulty, flawed, or simply unsafe in the first place.

Of course, double *insulation (missauto correction). I've never had a ground loop problem until I hooked up the NAD C658 for the first time to my AVR. After calling NAD support, they simply told me to replace the supplied 3 prong power cord with a commercial two prong IEC cord, and the noise has resolved. I've noticed that only "audiophile grade" products use earth grounding in audio gear. You'll never see Denon or Yamaha do it. When the audio signal is galvanically connected to earth ground, and you have at least two audio devices with earth paths, you increase the chance for ground loops and other noises.
 

EB1000

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Earth grounded is still the best practice for balanced connections. AVRs usually have only unbalanced connections, where isolated makes sense.


So, you're saying that Yamaha engineers are not aware of that??The new RX-A8A with balanced connection and no earth grounding...

Again, it creates more problems than solves.

A8A.png
 

solderdude

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Is the signal ground tied to the enclosure somewhere ?
When one connects more than one device there can still be groundloops through the RCA grounds of devices.
In that case the enclosure will most likely still be grounded via one of the connected devices.
Only the power supply inside will be double insulated and encased so mains cannot make contact with the enclosure.

The amp from the OP only has L and R input and balanced at that. Not comparable to complicated multi input AVR's.
 
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