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Running an amplifier unearthed



 
 
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  #1 (permalink)  
Old November 29th 17, 03:54 PM posted to uk.rec.audio
Johnny B Good
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Posts: 65
Default Running an amplifier unearthed

On Wed, 29 Nov 2017 13:09:28 +0000, Dave Plowman (News) wrote:

In article
,
D.M. Procida wrote:
If you read uk.d-i-y, you may have seen a thread ("This appliance must
be earthed") about Dutch mains sockets, which are often unearthed.


If I plug a Cyrus 1 amplifier (which has an extremely metal case and a
stern label saying "This appliance must be earthed") into an unearthed
socket, do I risk death by electrocution, or worse, poorer sound
quality?


The warning simply means the construction doesn't conform to the EU
requirements of a device with metal parts and no earth. Assuming it is
in good condition, I doubt you'd get electrocuted by it with no earth.

Noise figures as part of an installation may be poorer, though.


It makes sense to hard earth the amplifier and utilise the
'interconnects's signal earths to provide safety earthing of the
peripheral sources (TT. tuner, legacy optical disk player and tape deck
(s)). However, take note that phono plugs can sometimes prove ineffective
in earthing due to mismatches in the socket/plug dimensions so you need
to take care in your choice of phono plugs if you're going to rely upon
these interconnects to act as safety earths for your peripherals.

One sure fire way to provide safety earthing on peripheral kit
independent of signal earthing is to use a pair of 6A rated silicon
diodes wired in anti-parallel with a 100 ohm resistor and a 100nF
capacitor (all in parallel) in series with the safety earth connection
with a 1A safety fuse in each individual peripheral's mains supply
connection.

Under normal operating conditions, the signal earths will short out the
100 ohm resistor and the diodes high impedance at sub 500mV peak
voltages, effectively leaving the 'safety earth' connection in a state of
'disconnect' whilst still providing an effective safety earth in the
event of a fault.

One final note, it's good practice to power all of the components of a
"separates" Hi-Fi setup from a single ring main socket[1] via a quality
mains multi-socket extension lead or specialist connection strip. This
neatly isolates ground loop currents that can occur when using different
sockets on a ring main due to induced currents from heavy loads such as
washing machines, toasters, kettles etc.

[1] You can regard double/triple socket outlets (as well as adjacent
single/double/triple socket outlets) as being effectively a single outlet
in this case which can neatly do away with the need for a multi outlet
mains lead extension socket.

--
Johnny B Good
  #2 (permalink)  
Old November 29th 17, 05:20 PM posted to uk.rec.audio
Dave Plowman (News)
external usenet poster
 
Posts: 5,872
Default Running an amplifier unearthed

In article ,
Johnny B Good wrote:

One final note, it's good practice to power all of the components of a
"separates" Hi-Fi setup from a single ring main socket[1] via a quality
mains multi-socket extension lead or specialist connection strip. This
neatly isolates ground loop currents that can occur when using different
sockets on a ring main due to induced currents from heavy loads such as
washing machines, toasters, kettles etc.


I have a dedicated AV radial circuit here. With the earth for that going
light back to the house earth. Not sure that bit makes any difference,
though, but no big deal when installing it.

--
*INDECISION is the key to FLEXIBILITY *

Dave Plowman London SW
To e-mail, change noise into sound.
  #3 (permalink)  
Old November 29th 17, 06:04 PM posted to uk.rec.audio
Johnny B Good
external usenet poster
 
Posts: 65
Default Running an amplifier unearthed

On Wed, 29 Nov 2017 18:20:16 +0000, Dave Plowman (News) wrote:

In article ,
Johnny B Good wrote:

One final note, it's good practice to power all of the components of a
"separates" Hi-Fi setup from a single ring main socket[1] via a quality
mains multi-socket extension lead or specialist connection strip. This
neatly isolates ground loop currents that can occur when using
different sockets on a ring main due to induced currents from heavy
loads such as washing machines, toasters, kettles etc.


I have a dedicated AV radial circuit here. With the earth for that going
light back to the house earth. Not sure that bit makes any difference,
though, but no big deal when installing it.


It shouldn't. Assuming you only have a single safety earth connection to
the common signal ground return, the whole thing could be left to float
at whatever induced mains voltage happens to occur (including half mains
from filters or even a full contact to the live). It won't make any
difference although I'd be rather leery of actually touching any of the
kit if bringing your hand to within close proximity generates even the
slightest hint of mains hum.

--
Johnny B Good
  #4 (permalink)  
Old November 29th 17, 07:46 PM posted to uk.rec.audio
Don Pearce[_3_]
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Posts: 1,358
Default Running an amplifier unearthed

On Wed, 29 Nov 2017 19:04:32 GMT, Johnny B Good
wrote:

On Wed, 29 Nov 2017 18:20:16 +0000, Dave Plowman (News) wrote:

In article ,
Johnny B Good wrote:

One final note, it's good practice to power all of the components of a
"separates" Hi-Fi setup from a single ring main socket[1] via a quality
mains multi-socket extension lead or specialist connection strip. This
neatly isolates ground loop currents that can occur when using
different sockets on a ring main due to induced currents from heavy
loads such as washing machines, toasters, kettles etc.


I have a dedicated AV radial circuit here. With the earth for that going
light back to the house earth. Not sure that bit makes any difference,
though, but no big deal when installing it.


It shouldn't. Assuming you only have a single safety earth connection to
the common signal ground return, the whole thing could be left to float
at whatever induced mains voltage happens to occur (including half mains
from filters or even a full contact to the live). It won't make any
difference although I'd be rather leery of actually touching any of the
kit if bringing your hand to within close proximity generates even the
slightest hint of mains hum.


These days most grounds are heavily compromised by EMC from switching
power supplies coupled in through the Y1 capacitors. Hang enough of
those on a single circuit and eventually you can even trip the RCD
breaker.

d

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  #5 (permalink)  
Old November 30th 17, 09:02 AM posted to uk.rec.audio
Brian Gaff
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Posts: 637
Default Running an amplifier unearthed

Yes indeed, I was put of many moons ago from buying a Lecson system, you
remember the coloured sliders pre amp and the cylindrical power amp, as
touching the outside of the power amp while leaning on the radiator gave me
one heck of a belt. I did not enquire as to quite why this happened but it
seemed a trifle dodgy to me!
Brian

--
----- -
This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...

Blind user, so no pictures please!
"Don Pearce" wrote in message
...
On Wed, 29 Nov 2017 19:04:32 GMT, Johnny B Good
wrote:

On Wed, 29 Nov 2017 18:20:16 +0000, Dave Plowman (News) wrote:

In article ,
Johnny B Good wrote:

One final note, it's good practice to power all of the components of a
"separates" Hi-Fi setup from a single ring main socket[1] via a quality
mains multi-socket extension lead or specialist connection strip. This
neatly isolates ground loop currents that can occur when using
different sockets on a ring main due to induced currents from heavy
loads such as washing machines, toasters, kettles etc.

I have a dedicated AV radial circuit here. With the earth for that going
light back to the house earth. Not sure that bit makes any difference,
though, but no big deal when installing it.


It shouldn't. Assuming you only have a single safety earth connection to
the common signal ground return, the whole thing could be left to float
at whatever induced mains voltage happens to occur (including half mains
from filters or even a full contact to the live). It won't make any
difference although I'd be rather leery of actually touching any of the
kit if bringing your hand to within close proximity generates even the
slightest hint of mains hum.


These days most grounds are heavily compromised by EMC from switching
power supplies coupled in through the Y1 capacitors. Hang enough of
those on a single circuit and eventually you can even trip the RCD
breaker.

d

---
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus



  #6 (permalink)  
Old November 30th 17, 11:00 AM posted to uk.rec.audio
Dave Plowman (News)
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Posts: 5,872
Default Running an amplifier unearthed

In article ,
Johnny B Good wrote:
I have a dedicated AV radial circuit here. With the earth for that going
light back to the house earth. Not sure that bit makes any difference,
though, but no big deal when installing it.


It shouldn't. Assuming you only have a single safety earth connection to
the common signal ground return, the whole thing could be left to float
at whatever induced mains voltage happens to occur (including half mains
from filters or even a full contact to the live). It won't make any
difference although I'd be rather leery of actually touching any of the
kit if bringing your hand to within close proximity generates even the
slightest hint of mains hum.


Can you run that by me again? You can obviously get a potential difference
between two earths when any current flows. Like say between the earth to a
socket and the one to a light switch in the same room.

--
*WHERE DO FOREST RANGERS GO TO "GET AWAY FROM IT ALL?"

Dave Plowman London SW
To e-mail, change noise into sound.
  #7 (permalink)  
Old November 30th 17, 11:02 AM posted to uk.rec.audio
Dave Plowman (News)
external usenet poster
 
Posts: 5,872
Default Running an amplifier unearthed

In article ,
Don Pearce wrote:
It shouldn't. Assuming you only have a single safety earth connection to
the common signal ground return, the whole thing could be left to float
at whatever induced mains voltage happens to occur (including half mains
from filters or even a full contact to the live). It won't make any
difference although I'd be rather leery of actually touching any of the
kit if bringing your hand to within close proximity generates even the
slightest hint of mains hum.


These days most grounds are heavily compromised by EMC from switching
power supplies coupled in through the Y1 capacitors. Hang enough of
those on a single circuit and eventually you can even trip the RCD
breaker.


Which was the theory behind running my AV ground right back to the house
earthing point, rather than CU earth.

--
*Why don't sheep shrink when it rains?

Dave Plowman London SW
To e-mail, change noise into sound.
  #8 (permalink)  
Old November 30th 17, 11:05 AM posted to uk.rec.audio
Dave Plowman (News)
external usenet poster
 
Posts: 5,872
Default Running an amplifier unearthed

In article ,
Brian Gaff wrote:
Yes indeed, I was put of many moons ago from buying a Lecson system, you
remember the coloured sliders pre amp and the cylindrical power amp, as
touching the outside of the power amp while leaning on the radiator
gave me one heck of a belt. I did not enquire as to quite why this
happened but it seemed a trifle dodgy to me! Brian


You can get a small potential difference between earths grounded at a
common point when you measure well away from that point. Which is the
principle of equipotential bonding in a bathroom. But a large one means
something somewhere isn't right.

--
*Filthy stinking rich -- well, two out of three ain't bad

Dave Plowman London SW
To e-mail, change noise into sound.
  #9 (permalink)  
Old November 30th 17, 01:41 PM posted to uk.rec.audio
Brian Gaff
external usenet poster
 
Posts: 637
Default Running an amplifier unearthed

Yes knowing the shop concerned I strongly suspect the lack of earthing issue
mentioned elsewhere in this thread had come unstuck. Its very easy to get a
hum loop and feel that just unearthing one thing will fix it, but then
forgetting that no earth is possible not good either if anything went wrong
or just if a large capacitor is involved somewhere in the filtering.
Back when I was a spotty youth the trick we used to play on the girls
fitting components in the repair department was to leave a capacitor charged
up with a couple of hundred volts on their benches.

I'm sure you can imagine what tended to happen. Mind you there was one lady
who seemed to be immune to shocks. Probably had dry skin.
Brian

--
----- -
This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...

Blind user, so no pictures please!
"Dave Plowman (News)" wrote in message
...
In article ,
Brian Gaff wrote:
Yes indeed, I was put of many moons ago from buying a Lecson system, you
remember the coloured sliders pre amp and the cylindrical power amp, as
touching the outside of the power amp while leaning on the radiator
gave me one heck of a belt. I did not enquire as to quite why this
happened but it seemed a trifle dodgy to me! Brian


You can get a small potential difference between earths grounded at a
common point when you measure well away from that point. Which is the
principle of equipotential bonding in a bathroom. But a large one means
something somewhere isn't right.

--
*Filthy stinking rich -- well, two out of three ain't bad

Dave Plowman
London SW
To e-mail, change noise into sound.



  #10 (permalink)  
Old November 30th 17, 02:09 PM posted to uk.rec.audio
Johnny B Good
external usenet poster
 
Posts: 65
Default Running an amplifier unearthed

On Thu, 30 Nov 2017 12:00:07 +0000, Dave Plowman (News) wrote:

In article ,
Johnny B Good wrote:
I have a dedicated AV radial circuit here. With the earth for that
going light back to the house earth. Not sure that bit makes any
difference, though, but no big deal when installing it.


It shouldn't. Assuming you only have a single safety earth connection
to
the common signal ground return, the whole thing could be left to float
at whatever induced mains voltage happens to occur (including half
mains from filters or even a full contact to the live). It won't make
any difference although I'd be rather leery of actually touching any of
the kit if bringing your hand to within close proximity generates even
the slightest hint of mains hum.


Can you run that by me again? You can obviously get a potential
difference between two earths when any current flows. Like say between
the earth to a socket and the one to a light switch in the same room.


Provided all the Hi-Fi kit is bonded together via the signal earths and
only one point of connection to the signal earths is used to connect to
the ring main earth, it won't matter how much voltage is induced into the
mains earth. Indeed the whole lot can be left floating without detriment
to the audio signals passing between the separate components, even to the
point of having a connection (intentional or otherwise) to the mains live
where the only detriment would then be to the health of anyone grounding
such a high voltage to a real earth via their body.

Some of the internal signal wiring might be less than completely
screened from external electric fields which normally wouldn't be an
issue until you introduce a source of high voltage gradient (240v 50Hz ac
between you, at earth potential and the amplifier or TT wiring at 240v)
hence my semi facetious remark about being leery of inducing a faint hum
whenever you place a hand close to a less than completely screened piece
of Hi-Fi kit.

For line level signals, whatever minuscule currents might be induced
into the local safety earths of tape decks, tuners and other line out
sources will be way down in the noise. In any case, a lot of such kit is
usually double insulated, allowing the screen connections (ground
returns) to remain decoupled from all but the one and only connection
point to the safety earth, typically the main amplifier.

The one and only item of Hi-Fi kit that remains vulnerable to such hum
induction is the old fashioned TT cartridge wired directly into a remote
RIAA equalisation pre-amp located a metre or two away in the main
amplifier. The proper way to deal with this problem is simply to install
the RIAA pre-amp within the TT itself so that when the equalised signal
from the TT has to negotiate the link to the main amplifier, it can do so
at line level and appear as just another aux input signal labelled TT or
'Phono'.

--
Johnny B Good
 




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