I know that there is always furious debate on the audio groups about this,
but in all the years that I have been mending this stuff, I have never
actually been faced directly with it ...

Yesterday, a boat-anchor Yammy turned up from one of the high-end dealers
that I do work for, and with it was a power cable that the owner wants
fitting in place of the one that Yamaha saw fit to put on when they designed
it. This cable comprises a couple of metres of (20A?) three core rubber
power cable (the sort of stuff that you would use as the flexible 'tail' to
go from a wall plate to a storage heater, or maybe a hot water immersion
heater) plus a very ordinary UK 13A power plug on one end, and a reasonable
quality IEC straight plug on the other. The cost of this lead ? 100 UKP.
That's about $190 at the current exchange rate !! And he now wants to pay
the store to get me to fit it.

Now I'm actually not very happy about modifying anything to do with hot-side
power wiring, for obvious legal reasons, but my real question is about the
number of wires. Originally, the amp is fed with a standard 2 core power
lead. When this three core lead is fitted in its place, should I connect the
earth lead to the metal chassis ? I can't see that this should lead to any
potential safety issues, but as the amp was originally designed not to have
a power ground connected, might not connecting one lead to *more*
power-conducted noise getting in, actually making the performance *worse*
than the owner thinks that he is going to achieve, by his dubious mods ?

I have a contact within Yammy, who has direct access to the design boys back
in Japan, so I think that I am going to give him a call anyway, but I would
value the opinions of others on here as well.

Arfa

Arfa Daily wrote in message
...
I know that there is always furious debate on the audio groups about this,
but in all the years that I have been mending this stuff, I have never
actually been faced directly with it ...

Yesterday, a boat-anchor Yammy turned up from one of the high-end dealers
that I do work for, and with it was a power cable that the owner wants
fitting in place of the one that Yamaha saw fit to put on when they
designed
it. This cable comprises a couple of metres of (20A?) three core rubber
power cable (the sort of stuff that you would use as the flexible 'tail'
to
go from a wall plate to a storage heater, or maybe a hot water immersion
heater) plus a very ordinary UK 13A power plug on one end, and a
reasonable
quality IEC straight plug on the other. The cost of this lead ? 100 UKP.
That's about $190 at the current exchange rate !! And he now wants to pay
the store to get me to fit it.

Now I'm actually not very happy about modifying anything to do with
hot-side
power wiring, for obvious legal reasons, but my real question is about the
number of wires. Originally, the amp is fed with a standard 2 core power
lead. When this three core lead is fitted in its place, should I connect
the
earth lead to the metal chassis ? I can't see that this should lead to any
potential safety issues, but as the amp was originally designed not to
have
a power ground connected, might not connecting one lead to *more*
power-conducted noise getting in, actually making the performance *worse*
than the owner thinks that he is going to achieve, by his dubious mods ?

I have a contact within Yammy, who has direct access to the design boys
back
in Japan, so I think that I am going to give him a call anyway, but I
would
value the opinions of others on here as well.

Arfa



If the user-accessible part of the chassis is metal then that has to be
bonded to mains earth.
2 core is only allowed for double insulated kit in the UK.
Its not a quality of sound issue but a health and safety issue first and
foremost.

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/

N Cook wrote:
Arfa Daily wrote in message
...
I know that there is always furious debate on the audio groups about this,
but in all the years that I have been mending this stuff, I have never
actually been faced directly with it ...

Yesterday, a boat-anchor Yammy turned up from one of the high-end dealers
that I do work for, and with it was a power cable that the owner wants
fitting in place of the one that Yamaha saw fit to put on when they
designed
it. This cable comprises a couple of metres of (20A?) three core rubber
power cable (the sort of stuff that you would use as the flexible 'tail'
to
go from a wall plate to a storage heater, or maybe a hot water immersion
heater) plus a very ordinary UK 13A power plug on one end, and a
reasonable
quality IEC straight plug on the other. The cost of this lead ? 100 UKP.
That's about $190 at the current exchange rate !! And he now wants to pay
the store to get me to fit it.

Now I'm actually not very happy about modifying anything to do with
hot-side
power wiring, for obvious legal reasons, but my real question is about the
number of wires. Originally, the amp is fed with a standard 2 core power
lead. When this three core lead is fitted in its place, should I connect
the
earth lead to the metal chassis ? I can't see that this should lead to any
potential safety issues, but as the amp was originally designed not to
have
a power ground connected, might not connecting one lead to *more*
power-conducted noise getting in, actually making the performance *worse*
than the owner thinks that he is going to achieve, by his dubious mods ?

I have a contact within Yammy, who has direct access to the design boys
back
in Japan, so I think that I am going to give him a call anyway, but I
would
value the opinions of others on here as well.

Arfa



If the user-accessible part of the chassis is metal then that has to be
bonded to mains earth.
2 core is only allowed for double insulated kit in the UK.
Its not a quality of sound issue but a health and safety issue first and
foremost.

Some of the older 'pro' Yamaha power amps are 'double insulated' in that
the mains tranny is toroidal and totally isolated from chassis and all
mains potential is contained within double sleeving and neoprene boots
over the switches etc. The ground connection is provided via the signal
leads.

Ron(UK)

Arfa Daily wrote:
I know that there is always furious debate on the audio groups about this,
but in all the years that I have been mending this stuff, I have never
actually been faced directly with it ...

Yesterday, a boat-anchor Yammy turned up from one of the high-end dealers
that I do work for, and with it was a power cable that the owner wants
fitting in place of the one that Yamaha saw fit to put on when they designed
it. This cable comprises a couple of metres of (20A?) three core rubber
power cable (the sort of stuff that you would use as the flexible 'tail' to
go from a wall plate to a storage heater, or maybe a hot water immersion
heater) plus a very ordinary UK 13A power plug on one end, and a reasonable
quality IEC straight plug on the other. The cost of this lead ? 100 UKP.
That's about $190 at the current exchange rate !! And he now wants to pay
the store to get me to fit it.

**Personally, I won't do those jobs, UNLESS the cable is an approved
type. Examine the cable and I'll bet you won't find any of the relevant
electrical authority markings. It has probably not been tested nor
approved. Some of the leads I've exmamined barely have insulation
suitable for 12 Volts, let alone 240VAC. As for your earth question,
yes, I'd earth it.

Trevor Wilson

--
Posted via a free Usenet account from http://www.teranews.com

Arfa Daily wrote:

I know that there is always furious debate on the audio groups about this,
but in all the years that I have been mending this stuff, I have never
actually been faced directly with it ...

Yesterday, a boat-anchor Yammy turned up from one of the high-end dealers
that I do work for, and with it was a power cable that the owner wants
fitting in place of the one that Yamaha saw fit to put on when they designed
it.

LMAO !


This cable comprises a couple of metres of (20A?) three core rubber
power cable (the sort of stuff that you would use as the flexible 'tail' to
go from a wall plate to a storage heater, or maybe a hot water immersion
heater) plus a very ordinary UK 13A power plug on one end, and a reasonable
quality IEC straight plug on the other. The cost of this lead ? 100 UKP.
That's about $190 at the current exchange rate !! And he now wants to pay
the store to get me to fit it.

Now I'm actually not very happy about modifying anything to do with hot-side
power wiring, for obvious legal reasons, but my real question is about the
number of wires. Originally, the amp is fed with a standard 2 core power
lead.

So, the equipment is Class II (double insulated) and doesn't require an earth.


When this three core lead is fitted in its place, should I connect the
earth lead to the metal chassis ? I can't see that this should lead to any
potential safety issues, but as the amp was originally designed not to have
a power ground connected, might not connecting one lead to *more*
power-conducted noise getting in, actually making the performance *worse*
than the owner thinks that he is going to achieve, by his dubious mods ?

It might introduce 'hum loops' for sure.

It would be just desserts I think for the owner if that happned. It would serve
him right for being such a crackhead as to believe in magic cables.

What does the website of the cable manufacturer say about how its product works
? They may have some special magic view about the role of grounds !

Graham

"N Cook" wrote in message
...
Arfa Daily wrote in message
...
I know that there is always furious debate on the audio groups about
this,
but in all the years that I have been mending this stuff, I have never
actually been faced directly with it ...

Yesterday, a boat-anchor Yammy turned up from one of the high-end dealers
that I do work for, and with it was a power cable that the owner wants
fitting in place of the one that Yamaha saw fit to put on when they
designed
it. This cable comprises a couple of metres of (20A?) three core rubber
power cable (the sort of stuff that you would use as the flexible 'tail'
to
go from a wall plate to a storage heater, or maybe a hot water immersion
heater) plus a very ordinary UK 13A power plug on one end, and a
reasonable
quality IEC straight plug on the other. The cost of this lead ? 100 UKP.
That's about $190 at the current exchange rate !! And he now wants to pay
the store to get me to fit it.

Now I'm actually not very happy about modifying anything to do with
hot-side
power wiring, for obvious legal reasons, but my real question is about
the
number of wires. Originally, the amp is fed with a standard 2 core power
lead. When this three core lead is fitted in its place, should I connect
the
earth lead to the metal chassis ? I can't see that this should lead to
any
potential safety issues, but as the amp was originally designed not to
have
a power ground connected, might not connecting one lead to *more*
power-conducted noise getting in, actually making the performance *worse*
than the owner thinks that he is going to achieve, by his dubious mods ?

I have a contact within Yammy, who has direct access to the design boys
back
in Japan, so I think that I am going to give him a call anyway, but I
would
value the opinions of others on here as well.

Arfa



If the user-accessible part of the chassis is metal then that has to be
bonded to mains earth.
2 core is only allowed for double insulated kit in the UK.
Its not a quality of sound issue but a health and safety issue first and
foremost.


It is indeed a 'double insulated' item - as indeed most domestic equipment
these days is, irrespective of whether it has a metal chassis / case
accessible to the punter, or not. It of course carries the double insulated
symbol to show this to be the case. So what I was asking was not primarily a
health and safety issue, but a sound one, as the owner believes it to be. As
I said, I don't think that connecting a mains earth to the metalwork of such
an item - double insulated or not - represents any kind of safety issue, but
as the equipment was originally designed to operate without a connection
*directly* from the chassis to the mains power outlet, then it might in fact
make the noise performance worse than 'as-designed', rather than better, as
the nutcase who owns it, believes ...

Arfa
--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/

Trevor Wilson wrote:

Arfa Daily wrote:
I know that there is always furious debate on the audio groups about this,
but in all the years that I have been mending this stuff, I have never
actually been faced directly with it ...

Yesterday, a boat-anchor Yammy turned up from one of the high-end dealers
that I do work for, and with it was a power cable that the owner wants
fitting in place of the one that Yamaha saw fit to put on when they designed
it. This cable comprises a couple of metres of (20A?) three core rubber
power cable (the sort of stuff that you would use as the flexible 'tail' to
go from a wall plate to a storage heater, or maybe a hot water immersion
heater) plus a very ordinary UK 13A power plug on one end, and a reasonable
quality IEC straight plug on the other. The cost of this lead ? 100 UKP.
That's about $190 at the current exchange rate !! And he now wants to pay
the store to get me to fit it.

**Personally, I won't do those jobs, UNLESS the cable is an approved
type. Examine the cable and I'll bet you won't find any of the relevant
electrical authority markings. It has probably not been tested nor
approved. Some of the leads I've exmamined barely have insulation
suitable for 12 Volts, let alone 240VAC. As for your earth question,
yes, I'd earth it.

Good point.

To attach an unapproved cable would strictly be illegal. You could be held liable
for any consequences too.

Graham

"Arfa Daily" hath wroth:

I know that there is always furious debate on the audio groups about this,
but in all the years that I have been mending this stuff, I have never
actually been faced directly with it ...

Wrong class of customer. Such things tend to be purchased by people
with more money than technical abilities. Did you notice that the
cord is rather stiff? That's intentional as no self respecting
audiophile would hide such an expensive purchase behind their
equipment. It's made to be hung out the front of the rack or shelf,
where all can admire it.

Yesterday, a boat-anchor Yammy turned up from one of the high-end dealers
that I do work for, and with it was a power cable that the owner wants
fitting in place of the one that Yamaha saw fit to put on when they designed
it. This cable comprises a couple of metres of (20A?) three core rubber
power cable (the sort of stuff that you would use as the flexible 'tail' to
go from a wall plate to a storage heater, or maybe a hot water immersion
heater) plus a very ordinary UK 13A power plug on one end, and a reasonable
quality IEC straight plug on the other. The cost of this lead ? 100 UKP.
That's about $190 at the current exchange rate !! And he now wants to pay
the store to get me to fit it.

Ouch. One of these cables perhaps?
http://www.audioadvisor.com/products.asp?dept=25&view_all=true
Be sure to check out the $1,080 power cable.

There was an article in EDN on the topic a while back. Digging...
"OFC madness: Facts, not fantasy, regarding power cables for high-end
audio equipment."
http://www.edn.com/article/CA6418215.html

Now I'm actually not very happy about modifying anything to do with hot-side
power wiring, for obvious legal reasons, but my real question is about the
number of wires. Originally, the amp is fed with a standard 2 core power
lead. When this three core lead is fitted in its place, should I connect the
earth lead to the metal chassis ?

If it was 2 wire, it would need to be double insulated. Grounding the
chassis is always a good thing (unless it's a 40 year old AC-DC power
supply). Yeah, I would ground it.

I can't see that this should lead to any
potential safety issues, but as the amp was originally designed not to have
a power ground connected, might not connecting one lead to *more*
power-conducted noise getting in, actually making the performance *worse*
than the owner thinks that he is going to achieve, by his dubious mods ?

Only if the AC power line noise were fairly high level (several volts)
and the power supply design was relying on the common mode rejection
of the AC power cord to remove the noise. A rather crude power line
noise filter will remove all of that.

I have a contact within Yammy, who has direct access to the design boys back
in Japan, so I think that I am going to give him a call anyway, but I would
value the opinions of others on here as well.

Don't give them any ideas, or we may be plagued with $200 replacement
power cords.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

If the user-accessible part of the chassis is metal then that has to be
bonded to mains earth.
2 core is only allowed for double insulated kit in the UK.
Its not a quality of sound issue but a health and safety issue first and
foremost.



I've never seen a piece of consumer A/V gear with a grounded power cord,
regardless of what the case is made of, but it certainly won't hurt anything
to ground it.


Maybe you ought to manufacture some of these obscenely expensive power cords
yourself, obviously suckers will buy them.

Arfa Daily wrote:
"N Cook" wrote in message
...
Arfa Daily wrote in message
...
I know that there is always furious debate on the audio groups about
this,
but in all the years that I have been mending this stuff, I have never
actually been faced directly with it ...

Yesterday, a boat-anchor Yammy turned up from one of the high-end dealers
that I do work for, and with it was a power cable that the owner wants
fitting in place of the one that Yamaha saw fit to put on when they
designed
it. This cable comprises a couple of metres of (20A?) three core rubber
power cable (the sort of stuff that you would use as the flexible 'tail'
to
go from a wall plate to a storage heater, or maybe a hot water immersion
heater) plus a very ordinary UK 13A power plug on one end, and a
reasonable
quality IEC straight plug on the other. The cost of this lead ? 100 UKP.
That's about $190 at the current exchange rate !! And he now wants to pay
the store to get me to fit it.

Now I'm actually not very happy about modifying anything to do with
hot-side
power wiring, for obvious legal reasons, but my real question is about
the
number of wires. Originally, the amp is fed with a standard 2 core power
lead. When this three core lead is fitted in its place, should I connect
the
earth lead to the metal chassis ? I can't see that this should lead to
any
potential safety issues, but as the amp was originally designed not to
have
a power ground connected, might not connecting one lead to *more*
power-conducted noise getting in, actually making the performance *worse*
than the owner thinks that he is going to achieve, by his dubious mods ?

I have a contact within Yammy, who has direct access to the design boys
back
in Japan, so I think that I am going to give him a call anyway, but I
would
value the opinions of others on here as well.

Arfa


If the user-accessible part of the chassis is metal then that has to be
bonded to mains earth.
2 core is only allowed for double insulated kit in the UK.
Its not a quality of sound issue but a health and safety issue first and
foremost.


It is indeed a 'double insulated' item - as indeed most domestic equipment
these days is, irrespective of whether it has a metal chassis / case
accessible to the punter, or not. It of course carries the double insulated
symbol to show this to be the case. So what I was asking was not primarily a
health and safety issue, but a sound one, as the owner believes it to be. As
I said, I don't think that connecting a mains earth to the metalwork of such
an item - double insulated or not - represents any kind of safety issue, but
as the equipment was originally designed to operate without a connection
*directly* from the chassis to the mains power outlet, then it might in fact
make the noise performance worse than 'as-designed', rather than better, as
the nutcase who owns it, believes ...

Arfa
--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/






Hooking up mains plug ground to all audio equipment produces
very nice ground loops. So I hope the customer is going to enjoy
the nice 50 or 60 HZ hum and its harmonics.......
A cluster of audio equipment should be grouned at one point
only to avoid loops.

James Sweet wrote:

If the user-accessible part of the chassis is metal then that has to be
bonded to mains earth.
2 core is only allowed for double insulated kit in the UK.
Its not a quality of sound issue but a health and safety issue first and
foremost.

I've never seen a piece of consumer A/V gear with a grounded power cord,
regardless of what the case is made of, but it certainly won't hurt anything
to ground it.

It MAY create problems. A grounded case will almost certainly ground the outers
of the RCA jacks. That will provide a path to ground for any leakage currents
and in turn that may result in 'hum' as currents flow where they weren't
intended to.

Graham

On Thu, 27 Sep 2007 08:50:58 GMT, "Arfa Daily"
put finger to keyboard and composed:

I know that there is always furious debate on the audio groups about this,
but in all the years that I have been mending this stuff, I have never
actually been faced directly with it ...

Yesterday, a boat-anchor Yammy turned up from one of the high-end dealers
that I do work for, and with it was a power cable that the owner wants
fitting in place of the one that Yamaha saw fit to put on when they designed
it. This cable comprises a couple of metres of (20A?) three core rubber
power cable (the sort of stuff that you would use as the flexible 'tail' to
go from a wall plate to a storage heater, or maybe a hot water immersion
heater) plus a very ordinary UK 13A power plug on one end, and a reasonable
quality IEC straight plug on the other. The cost of this lead ? 100 UKP.
That's about $190 at the current exchange rate !! And he now wants to pay
the store to get me to fit it.

Now I'm actually not very happy about modifying anything to do with hot-side
power wiring, for obvious legal reasons, but my real question is about the
number of wires. Originally, the amp is fed with a standard 2 core power
lead. When this three core lead is fitted in its place, should I connect the
earth lead to the metal chassis ? I can't see that this should lead to any
potential safety issues, but as the amp was originally designed not to have
a power ground connected, might not connecting one lead to *more*
power-conducted noise getting in, actually making the performance *worse*
than the owner thinks that he is going to achieve, by his dubious mods ?

This month's Australian Silicon Chip magazine has an article on the
hum and RF noise produced by 2-pronged DVD players. The author(s)
tested quite a few of these players by connecting them to an old
3-pronged amp. They found that audible hum was introduced when earth
current flowed from a player's switchmode PSU to the amplifier's earth
via the analogue signal leads. Additional radiated interference was
attributed to the digital noise produced by the main decoder chip, and
to the 100kHz switching frequency of the PSU.

The only solution recommended by the author(s) was to replace the SMPS
with a linear one. Doing so eliminated the hum and PSU noise.

I have a contact within Yammy, who has direct access to the design boys back
in Japan, so I think that I am going to give him a call anyway, but I would
value the opinions of others on here as well.

Arfa

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.

Franc Zabkar wrote:

This month's Australian Silicon Chip magazine has an article on the
hum and RF noise produced by 2-pronged DVD players. The author(s)
tested quite a few of these players by connecting them to an old
3-pronged amp. They found that audible hum was introduced when earth
current flowed from a player's switchmode PSU to the amplifier's earth
via the analogue signal leads.

100% predictable. The usual cuplrit is the Y caps in the SMPS of the 2 wire
equipment which results is significant (but legal) leakage current of up to
around 2 mA. Of course, this won't happen if the amplifier is a 2-wire type too
since there's no earth for the current to flow to.

So, adding an earth to a Class II amplifier is likely to add 'hum'. Simple
really.

Graham

On Sun, 30 Sep 2007 00:49:12 +0100, Eeyore
put finger to keyboard and
composed:

Franc Zabkar wrote:

This month's Australian Silicon Chip magazine has an article on the
hum and RF noise produced by 2-pronged DVD players. The author(s)
tested quite a few of these players by connecting them to an old
3-pronged amp. They found that audible hum was introduced when earth
current flowed from a player's switchmode PSU to the amplifier's earth
via the analogue signal leads.

100% predictable. The usual cuplrit is the Y caps in the SMPS of the 2 wire
equipment which results is significant (but legal) leakage current of up to
around 2 mA. Of course, this won't happen if the amplifier is a 2-wire type too
since there's no earth for the current to flow to.

The same article measured the chassis potentials of the various
devices. One measured 81VAC with respect to earth, others measured
115-117VAC. In some devices the A-E and N-E RFI suppression caps were
not installed. However, all appeared to have a coupling cap between
the AC and DC sides of the switching transformer. One end of this cap
appears to be connected to the case, while the other end probably goes
to the negative side of the bridge.

I would think that it would still be possible for a noise current to
flow from one case to another if the chassis potentials were
significantly different.

So, adding an earth to a Class II amplifier is likely to add 'hum'. Simple
really.

Graham

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.

Franc Zabkar wrote:

Eeyore put finger to keyboard and composed:
Franc Zabkar wrote:

This month's Australian Silicon Chip magazine has an article on the
hum and RF noise produced by 2-pronged DVD players. The author(s)
tested quite a few of these players by connecting them to an old
3-pronged amp. They found that audible hum was introduced when earth
current flowed from a player's switchmode PSU to the amplifier's earth
via the analogue signal leads.

100% predictable. The usual cuplrit is the Y caps in the SMPS of the 2 wire
equipment which results is significant (but legal) leakage current of up to
around 2 mA. Of course, this won't happen if the amplifier is a 2-wire type too
since there's no earth for the current to flow to.

The same article measured the chassis potentials of the various
devices. One measured 81VAC with respect to earth, others measured
115-117VAC. In some devices the A-E and N-E RFI suppression caps were
not installed. However, all appeared to have a coupling cap between
the AC and DC sides of the switching transformer.

That one's a killer. The idea of it is to return switching noise on the output to
the low impedance of the bulk filter cap. Of course it also results in the high
frequency content of rectified AC being passed to the secondary side.


One end of this cap appears to be connected to the case, while the other end
probably goes
to the negative side of the bridge.

Or positive. Doesn't matter which especially but returning it to the negative side
can interfere with the regulation circuitry operation.


I would think that it would still be possible for a noise current to
flow from one case to another if the chassis potentials were
significantly different.

I suppose that must be possible but maybe it'll be of a smaller magnitude.

Graham

In article ,
N Cook wrote:
If the user-accessible part of the chassis is metal then that has to be
bonded to mains earth.
2 core is only allowed for double insulated kit in the UK.
Its not a quality of sound issue but a health and safety issue first and
foremost.

Not so. If the power supply and mains wiring etc within the amp conforms
to the standard there is no need to earth the metal chassis. Otherwise
every single metal cased amp etc would have the casing earthed and hum
loops would abound.

--
*Born free - taxed to death *

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

In article J8RKi.4028$Wo4.3426@trnddc03,
James Sweet wrote:
I've never seen a piece of consumer A/V gear with a grounded power cord,
regardless of what the case is made of, but it certainly won't hurt
anything to ground it.

Lots of Far East gear in the early days had grounded cases to pass UK regs
without going to the cost of double insulation. And when you plugged
separates from the same maker together using the provided leads you got a
ground loop...

Grounding an amp case only may well be ok since that will be the 'master'
part of any system. But doing the same to other separates will almost
certainly create hum.

--
*In "Casablanca", Humphrey Bogart never said "Play it again, Sam" *

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