[Eeyore]

Don Pearce wrote:

Eeyore wrote:
Don Pearce wrote:
"Arny Krueger" wrote:
"Eeyore" wrote in

Balanced wiring only gives you an advantage if the
equipment is balanced. With clever wiring it's only
actually necessary for either the 'sending' or
'receiving' equipment to have a balanced input or ouput
but you need to know what you're doing in this case.

I know the strong advantage that balanced inputs give, but what advantage do
you get from an electronically-balanced output driving an unbalanced input?


Provided you have an appropriate balun, like a transformer at the
input, you get all of the advantages.

You don't even need a balun if you wire it to take advantage of the balanced
output. Just take the balaned output (low/cold) to the destination input 'ground'
and the output (high/hot) to the destination input and do not connect the screen
at the destination.

No longer balanced - not even a tiny bit.

It's differential and for all practical purpose does the same job.

Graham

[Eeyore]

Serge Auckland wrote:

I have assumed that the OP will run balanced

Big mistake and almost certainly completely unnecessary.

Graham

[Don Pearce]

On Tue, 15 Apr 2008 19:01:29 +0100, Eeyore
wrote:



Don Pearce wrote:

Eeyore wrote:
Arny Krueger wrote:
"Don Pearce" wrote in message

Ah - ok. The answer to your question is that it is
impossible to drive an unbalanced input from a balanced
output.

Good, then I'm not losing my mind! ;-)

Don is talking CRAP unfortunately.


Only when the following subsequent is deleted. One unbalanced
connection unbalances the entire circuit.

Read what I posted carefully. I AM correct.

Balanced is somewhat different to differential in detail and one or the
other may be equally suitable as a 'hum reducing' strategy.

Graham

Balanced implies differential - that is what forms the balance. If you
take twisted pair with something on the far end - a mic for example -
and connect it to an unbalanced input, one of the pair is shorted to
ground, the other connected to the input; result is hum.

Of course balanced implies that it is balanced with respect to
something - ground usually, but not necessarily. It is quite possible
to have a balanced system running entirely on batteries.

d

--

d

[Don Pearce]

On Tue, 15 Apr 2008 19:02:28 +0100, Eeyore
wrote:



Don Pearce wrote:

Eeyore wrote:
Don Pearce wrote:
"Arny Krueger" wrote:
"Eeyore" wrote in

Balanced wiring only gives you an advantage if the
equipment is balanced. With clever wiring it's only
actually necessary for either the 'sending' or
'receiving' equipment to have a balanced input or ouput
but you need to know what you're doing in this case.

I know the strong advantage that balanced inputs give, but what advantage do
you get from an electronically-balanced output driving an unbalanced input?


Provided you have an appropriate balun, like a transformer at the
input, you get all of the advantages.

You don't even need a balun if you wire it to take advantage of the balanced
output. Just take the balaned output (low/cold) to the destination input 'ground'
and the output (high/hot) to the destination input and do not connect the screen
at the destination.

No longer balanced - not even a tiny bit.

It's differential and for all practical purpose does the same job.

No, it isn't. You have one wire shorted to ground, and the other
terminated with an amp input. The two wires are no longer equal and
opposite, so what should be common mode pickup becomes differential
mode.


--

d

[Eeyore]

Don Pearce wrote:

Eeyore wrote:
Don Pearce wrote:
Eeyore wrote:
Arny Krueger wrote:
"Don Pearce" wrote in message

Ah - ok. The answer to your question is that it is
impossible to drive an unbalanced input from a balanced
output.

Good, then I'm not losing my mind! ;-)

Don is talking CRAP unfortunately.


Only when the following subsequent is deleted. One unbalanced
connection unbalances the entire circuit.

Read what I posted carefully. I AM correct.

Balanced is somewhat different to differential in detail and one or the
other may be equally suitable as a 'hum reducing' strategy.


Balanced implies differential - that is what forms the balance.

Define differential and balance in that case !

One very important difference is that balanced circuits should be of equal
impedance on both legs. This is not a requirement of differential circuits.
Here lies a very important difference as to how they function and where they
are most or beneficially applicable.


If you take twisted pair with something on the far end - a mic for example
-
and connect it to an unbalanced input, one of the pair is shorted to
ground, the other connected to the input; result is hum.

NO. That's a floating circuit and as long as it's screened there absolutely
NO reason it should hum whatever.


Of course balanced implies that it is balanced with respect to
something - ground usually, but not necessarily.

Not necessarily with regard to voltage to ground though ! ;~)
Absolutely not in fact. Think how telephones work.


It is quite possible to have a balanced system running entirely on
batteries.

Not quite sure what your point is there.

Graham

[Eeyore]

Don Pearce wrote:

Eeyore wrote:
Don Pearce wrote:
Eeyore wrote:
Don Pearce wrote:
"Arny Krueger" wrote:
"Eeyore" wrote in

Balanced wiring only gives you an advantage if the
equipment is balanced. With clever wiring it's only
actually necessary for either the 'sending' or
'receiving' equipment to have a balanced input or ouput
but you need to know what you're doing in this case.

I know the strong advantage that balanced inputs give, but what advantage do
you get from an electronically-balanced output driving an unbalanced input?


Provided you have an appropriate balun, like a transformer at the
input, you get all of the advantages.

You don't even need a balun if you wire it to take advantage of the balanced
output. Just take the balaned output (low/cold) to the destination input 'ground'
and the output (high/hot) to the destination input and do not connect the screen
at the destination.

No longer balanced - not even a tiny bit.

It's differential and for all practical purpose does the same job.

No, it isn't. You have one wire shorted to ground,

Which wire is shorted to ground ? Ever heard of a ground reference ?


and the other terminated with an amp input. The two wires are no longer equal and
opposite, so what should be common mode pickup becomes differential
mode.

You're missing the point.

Graham

[jakdedert]

Don Pearce wrote:
On Tue, 15 Apr 2008 19:02:28 +0100, Eeyore
wrote:


Don Pearce wrote:

Eeyore wrote:
Don Pearce wrote:
"Arny Krueger" wrote:
"Eeyore" wrote in

Balanced wiring only gives you an advantage if the
equipment is balanced. With clever wiring it's only
actually necessary for either the 'sending' or
'receiving' equipment to have a balanced input or ouput
but you need to know what you're doing in this case.
I know the strong advantage that balanced inputs give, but what advantage do
you get from an electronically-balanced output driving an unbalanced input?

Provided you have an appropriate balun, like a transformer at the
input, you get all of the advantages.
You don't even need a balun if you wire it to take advantage of the balanced
output. Just take the balaned output (low/cold) to the destination input 'ground'
and the output (high/hot) to the destination input and do not connect the screen
at the destination.
No longer balanced - not even a tiny bit.
It's differential and for all practical purpose does the same job.

No, it isn't. You have one wire shorted to ground, and the other
terminated with an amp input. The two wires are no longer equal and
opposite, so what should be common mode pickup becomes differential
mode.


I dimly comprehend what he's talking about. Since there is no actual
earth ground at the unbalanced input--and no connection to the output
equipment ground--the ground connection plus the signal hot would seem
to form a differential input. Possibly there is some issue with his/my
logic, but it would seem to be feasible.

Still, IMM, it would be safer to simply isolate and balance the line
conventionally...either with transformers or active circuits on both
ends. Also, the OP is unlikely to have a true balanced output on the
gear which feeds the cable, so at least some balancing circuitry is
indicated.

jak

[Don Pearce]

On Tue, 15 Apr 2008 19:48:52 +0100, Eeyore
wrote:



Don Pearce wrote:

Eeyore wrote:
Don Pearce wrote:
Eeyore wrote:
Arny Krueger wrote:
"Don Pearce" wrote in message

Ah - ok. The answer to your question is that it is
impossible to drive an unbalanced input from a balanced
output.

Good, then I'm not losing my mind! ;-)

Don is talking CRAP unfortunately.


Only when the following subsequent is deleted. One unbalanced
connection unbalances the entire circuit.

Read what I posted carefully. I AM correct.

Balanced is somewhat different to differential in detail and one or the
other may be equally suitable as a 'hum reducing' strategy.


Balanced implies differential - that is what forms the balance.

Define differential and balance in that case !

One very important difference is that balanced circuits should be of equal
impedance on both legs. This is not a requirement of differential circuits.
Here lies a very important difference as to how they function and where they
are most or beneficially applicable.


If you take twisted pair with something on the far end - a mic for example
-
and connect it to an unbalanced input, one of the pair is shorted to
ground, the other connected to the input; result is hum.

NO. That's a floating circuit and as long as it's screened there absolutely
NO reason it should hum whatever.


We're talking twisted pair, not screened.


Of course balanced implies that it is balanced with respect to
something - ground usually, but not necessarily.

Not necessarily with regard to voltage to ground though ! ;~)
Absolutely not in fact. Think how telephones work.


It is quite possible to have a balanced system running entirely on
batteries.

Not quite sure what your point is there.

I'm saying that it doesn't actually need to be balanced with respect
to something specific.

Graham


All signals are by definition differential - you have to have a
voltage between two point that changes in order to get carriers
stirring in transistors. One of those points will be ground in an
unbalanced system, or an equal-and-opposite input in a balanced
system.

That is the literal situation, but now for the convention. When we
talk about a differential input, we mean there is one terminal
labelled plus, and one labelled minus. That is the difference between
a differential and a single ended input; both require a voltage
difference to operate, but the differential input uses two equal and
opposite voltages - that is the same thing as a balanced input.


--

d

[Don Pearce]

On Tue, 15 Apr 2008 19:50:07 +0100, Eeyore
wrote:



Don Pearce wrote:

Eeyore wrote:
Don Pearce wrote:
Eeyore wrote:
Don Pearce wrote:
"Arny Krueger" wrote:
"Eeyore" wrote in

Balanced wiring only gives you an advantage if the
equipment is balanced. With clever wiring it's only
actually necessary for either the 'sending' or
'receiving' equipment to have a balanced input or ouput
but you need to know what you're doing in this case.

I know the strong advantage that balanced inputs give, but what advantage do
you get from an electronically-balanced output driving an unbalanced input?


Provided you have an appropriate balun, like a transformer at the
input, you get all of the advantages.

You don't even need a balun if you wire it to take advantage of the balanced
output. Just take the balaned output (low/cold) to the destination input 'ground'
and the output (high/hot) to the destination input and do not connect the screen
at the destination.

No longer balanced - not even a tiny bit.

It's differential and for all practical purpose does the same job.

No, it isn't. You have one wire shorted to ground,

Which wire is shorted to ground ? Ever heard of a ground reference ?


and the other terminated with an amp input. The two wires are no longer equal and
opposite, so what should be common mode pickup becomes differential
mode.

You're missing the point.


Clearly - what is it?


--

d

[Richard Crowley]

"jakdedert" wrote ...
I dimly comprehend what he's talking about. Since there is no actual
earth ground at the unbalanced input--and no connection to the output
equipment ground--the ground connection plus the signal hot would seem to
form a differential input. Possibly there is some issue with his/my
logic, but it would seem to be feasible.

In these days of home entertainment systems which include
video equipment, the chances of a completely ungrounded
system is also slim to none. Whether video comes from a
cable system or from a DBS satellite dish/receiver, they are
very likely grounded, and a very common cause of ground-
caused problems, notoriously hum. RF transformers which
break this ground connection are becoming common in the
home-theatre industry.

Still, IMM, it would be safer to simply isolate and balance the line
conventionally...either with transformers or active circuits on both ends.
Also, the OP is unlikely to have a true balanced output on the gear which
feeds the cable, so at least some balancing circuitry is indicated.

Indeed. In ideal conditions you could get away without it.
That appears to be Graham's position. Unfortunately he
seems to live in a very enchanted place compared to the
real world out here.

[Eeyore]

Richard Crowley wrote:

"jakdedert" wrote ...
I dimly comprehend what he's talking about. Since there is no actual
earth ground at the unbalanced input--and no connection to the output
equipment ground--the ground connection plus the signal hot would seem to
form a differential input. Possibly there is some issue with his/my
logic, but it would seem to be feasible.

In these days of home entertainment systems which include
video equipment, the chances of a completely ungrounded
system is also slim to none. Whether video comes from a
cable system or from a DBS satellite dish/receiver, they are
very likely grounded, and a very common cause of ground-
caused problems, notoriously hum. RF transformers which
break this ground connection are becoming common in the
home-theatre industry.

NONE of the home AV style equipment I have here has a mains earth, ALL of it has
only 2 conductor mains leads.

I'm talking about the CD player, DVD, cable TV tuner, VCR, Amplifier and tape
deck. I dare say the screen of the incoming cable feed is grounded but there's
no way for it to make a loop.

Graham

[Richard Crowley]

"Eeyore" wrote ...
NONE of the home AV style equipment I have here has a
mains earth, ALL of it has only 2 conductor mains leads.

It is not the mains power that is earthed/grounded.
It is the RF input cable (from either the community
cable distro system, or from the TVRO antenna).
Both are required to be bonded to earth by local
regulations virtually across the USA. It is a big
problem over here on our side of the pond.

TVRO antennas are not as much problem, because
they are grounded right at the customer's premises.
But cable systems are frequently grounded farther
away (back at the nearest main amplifier, etc.) and
voltage differentials on the order of 50V are not
unheard of (between the cable shield and local
ground.)

[Eeyore]

Richard Crowley wrote:

"Eeyore" wrote ...
NONE of the home AV style equipment I have here has a
mains earth, ALL of it has only 2 conductor mains leads.

It is not the mains power that is earthed/grounded.
It is the RF input cable (from either the community
cable distro system, or from the TVRO antenna).

There's only ONE of those hence no possibility of a LOOP !


Graham

[Serge Auckland[_2_]]

"Eeyore" wrote in message
...


Richard Crowley wrote:

"jakdedert" wrote ...
I dimly comprehend what he's talking about. Since there is no actual
earth ground at the unbalanced input--and no connection to the output
equipment ground--the ground connection plus the signal hot would seem
to
form a differential input. Possibly there is some issue with his/my
logic, but it would seem to be feasible.

In these days of home entertainment systems which include
video equipment, the chances of a completely ungrounded
system is also slim to none. Whether video comes from a
cable system or from a DBS satellite dish/receiver, they are
very likely grounded, and a very common cause of ground-
caused problems, notoriously hum. RF transformers which
break this ground connection are becoming common in the
home-theatre industry.

NONE of the home AV style equipment I have here has a mains earth, ALL of
it has
only 2 conductor mains leads.

I'm talking about the CD player, DVD, cable TV tuner, VCR, Amplifier and
tape
deck. I dare say the screen of the incoming cable feed is grounded but
there's
no way for it to make a loop.

Graham


And there, I think, is the core of the issue. You are talking about
equipment that floats free of earth, and you're using the whole equipment as
a differential input. However, as the balance to earth is very poor, the
common-mode rejection will be very small. It may avoid earth-loops, but will
do little to avoid other forms of interference. It is also highly dependant
on there being no, or at best only one connection to earth anywhere in the
system. As soon as you have two, the potential for hum loops exists. Far
better in my mind is to balance everything properly.

To paraphrase I think, John Linsley Hood, you can always cut down on safety
margins if you have complete control over circumstances. In your case,
anyone making an equipment change at some stage in the future could set up a
hum-loop.

S.

--
http://audiopages.googlepages.com

[Eeyore]

Serge Auckland wrote:

"Eeyore" wrote
Richard Crowley wrote:
"jakdedert" wrote ...

I dimly comprehend what he's talking about. Since there is no actual
earth ground at the unbalanced input--and no connection to the output
equipment ground--the ground connection plus the signal hot would seem
to
form a differential input. Possibly there is some issue with his/my
logic, but it would seem to be feasible.

In these days of home entertainment systems which include
video equipment, the chances of a completely ungrounded
system is also slim to none. Whether video comes from a
cable system or from a DBS satellite dish/receiver, they are
very likely grounded, and a very common cause of ground-
caused problems, notoriously hum. RF transformers which
break this ground connection are becoming common in the
home-theatre industry.

NONE of the home AV style equipment I have here has a mains earth, ALL of
it has
only 2 conductor mains leads.

I'm talking about the CD player, DVD, cable TV tuner, VCR, Amplifier and
tape deck. I dare say the screen of the incoming cable feed is grounded but
there's no way for it to make a loop.


And there, I think, is the core of the issue. You are talking about
equipment that floats free of earth,

Class II equipment yes. Like most hi-fi and AV these days.


and you're using the whole equipment as a differential input.

*Floating* actually.


However, as the balance to earth is very poor, the
common-mode rejection will be very small. It may avoid earth-loops, but will
do little to avoid other forms of interference.

Quite possibly so but all we want to avoid is 50Hz hum and it'll do that JUST
FINE !

Stop trying to invent non-existent problems. There aren't any.

Graham

[Eeyore]

Serge Auckland wrote:

It is also highly dependant on there being no, or at best only one connection
to earth

Absolutely NOTHING wrong with ONE connection to earth.


anywhere in the system. As soon as you have two, the potential for hum loops
exists.

Isn't that EXACTLY what I said ?

Since there's no NEED for a mains earth on such kit .....


Graham

[Eeyore]

Serge Auckland wrote:

To paraphrase I think, John Linsley Hood, you can always cut down on safety
margins if you have complete control over circumstances.

There is NOTHING unsafe about Class II equipment. In fact it has to be
intrinsicly SAFER than earthed kit.


In your case, anyone making an equipment change at some stage in the future
could set up a
hum-loop.

COULD ? Why WOULD they.

You're inventing fictional problems again.

Graham

[Serge Auckland[_2_]]

"Eeyore" wrote in message
...


Serge Auckland wrote:

To paraphrase I think, John Linsley Hood, you can always cut down on
safety
margins if you have complete control over circumstances.

There is NOTHING unsafe about Class II equipment. In fact it has to be
intrinsicly SAFER than earthed kit.


In your case, anyone making an equipment change at some stage in the
future
could set up a
hum-loop.

COULD ? Why WOULD they.

You're inventing fictional problems again.

Graham


Not so much a case of inventing fictitional problems, just good engineering
practice. Whenever I implement any solution to a problem, I try and think of
what could possibly go wrong in the future and try to plan for it. If you're
sure there won't be any future changes, and you're only trying to avoid hum
loops, then your solution is probably fine. That, by the way, is what I
meant in paraphrasing J L-H. I wasn't suggesting your solution is unsafe,
just that if you solve a problem in the minimum way possible, you sacrifice
the flexibility of a better solution.

Interesting that your AV equipment is all ungrounded. Mine isn't. Some items
are ungrounded - DTTV box, DVD player, DVD recorder, but the main TV is
grounded, my CD player, pre-amp, and active 'speakers are all grounded.
Turntables are all grounded. It's a mixture, so your solution isn't
generally applicable.

S.

--
http://audiopages.googlepages.com

[Chris Hornbeck]

On Tue, 15 Apr 2008 09:39:00 -0400, "Arny Krueger"
wrote:

I know the strong advantage that balanced inputs give,
but what advantage do you get from an
electronically-balanced output driving an unbalanced
input?


Provided you have an appropriate balun, like a
transformer at the input, you get all of the advantages.

The balun just turns the unbalanced input into a balanced input. Therefore,
the basic answer I asked has not been answered.

A balun doesn't provide the same common-mode rejection
as a high impedance differential input (because degraded by
impedance interactions). Noise immunity is conferred by
the differential input, and *not* by the "balancing" per se.

This thread is typical of Usenet discussions where terms
are assumed rather than defined. Folks could understand each
other better if "balanced", differential", "floating" and
"common-mode rejection" were included up front. But hey,
that's life in cypherspace, ain't it?

And "balanced" is far and away the worst offender. Almost
universally misused.

Now here's a related question for all the Buckeroo's:
What advantage does a balanced-in-the-sense-of-equal-
voltages-and-equal-source-impedances-to-each-polarity-output
have over a balanced-in-the-sense-of-equal-source-
impedances-to-each-polarity-output-but-only-one-polarity-driven,
and assuming a true high impedance (non-interactive)
differential receiving input?

Much thanks, as always,

Chris Hornbeck

[Arny Krueger]

"Eeyore" wrote in
message
Serge Auckland wrote:

Whatever way you do it, I would not even think about
using unbalanced wiring however well screened, as once
incorporated in the house, it can't be changed.

For little more you can run screened twin and keep your
options open. That's probably the best advice. Cat 5 can
cause crosstalk trouble.

I recently specified the wiring for some long A/V runs at church. I found
shielded, stranded twisted pair from a number of sources for under $0.25 per
foot. I didn't have low resistance as a goal, but it turned out that the
price per foot was pretty constant down to 18 gauge so I went with the
heavier stuff.

[Richard Crowley]

"Eeyore" wrote ...
Richard Crowley wrote:

"Eeyore" wrote ...
NONE of the home AV style equipment I have here has a
mains earth, ALL of it has only 2 conductor mains leads.

It is not the mains power that is earthed/grounded.
It is the RF input cable (from either the community
cable distro system, or from the TVRO antenna).

There's only ONE of those hence no possibility of a LOOP !

Good. We'll remember that next time someone comes
here asking about their HT system hum problem, and
why it goes away when they disconnect the cable. We
will let you explain to them that the hum is only in
their imagination.

[Chris Hornbeck]

On Tue, 15 Apr 2008 19:04:10 -0700, "Richard Crowley"
wrote:

"Eeyore" wrote ...

It is not the mains power that is earthed/grounded.
It is the RF input cable (from either the community
cable distro system, or from the TVRO antenna).

There's only ONE of those hence no possibility of a LOOP !

Good. We'll remember that next time someone comes
here asking about their HT system hum problem, and
why it goes away when they disconnect the cable. We
will let you explain to them that the hum is only in
their imagination.

This kinda thing is a large part of my day-gig these
last coupla years. I used to give the information away
free to our "installer guys" and now I get paid
(peanuts) to fix these issues myself. It's what in
America is called "early retirement". Arf .

Ground loops *do not* require a perfect non-conductive
loop to matter. Just the opposite, in fact. Modern consumer
electronics has many amazingly diverse sources of ground
contamination, and all include some element of current
into a "nominal" ground.

IOW, there are no "grounds". The difference between our
preconceptions of "ground" and the reality are the crux
of the biscuit.


Ground loops are systemic and subtle, and include the
summed parasitic couplings from all devices' mains to
each device's nominal Earth. It's a non-trivial summation.

Much thanks, as alway,

Chris Hornbeck

[Eeyore]

Serge Auckland wrote:

"Eeyore" wrote
Serge Auckland wrote:

To paraphrase I think, John Linsley Hood, you can always cut down on
safety margins if you have complete control over circumstances.

There is NOTHING unsafe about Class II equipment. In fact it has to be
intrinsicly SAFER than earthed kit.


In your case, anyone making an equipment change at some stage in the
future could set up a hum-loop.

COULD ? Why WOULD they.

You're inventing fictional problems again.


Not so much a case of inventing fictitional problems, just good engineering
practice. Whenever I implement any solution to a problem, I try and think of
what could possibly go wrong in the future and try to plan for it.

All very well but if you introduce a hum loop you can add transformers THEN !
They're simply not NEEDED here !


If you're sure there won't be any future changes, and you're only trying to
avoid hum
loops, then your solution is probably fine.

It will be.


That, by the way, is what I
meant in paraphrasing J L-H. I wasn't suggesting your solution is unsafe,
just that if you solve a problem in the minimum way possible, you sacrifice
the flexibility of a better solution.

Interesting that your AV equipment is all ungrounded. Mine isn't. Some items
are ungrounded - DTTV box, DVD player, DVD recorder, but the main TV is
grounded, my CD player, pre-amp, and active 'speakers are all grounded.
Turntables are all grounded. It's a mixture, so your solution isn't
generally applicable.

A turntable does not need to be physically GROUNDED. Just connect its chassis to
the chassis of the amplifier with the cartridge preamp.

I haven't seen a TV with a ground conductor since just about forever btw.

Graham

[Eeyore]

Richard Crowley wrote:

"Eeyore" wrote ...
Richard Crowley wrote:
"Eeyore" wrote ...

NONE of the home AV style equipment I have here has a
mains earth, ALL of it has only 2 conductor mains leads.

It is not the mains power that is earthed/grounded.
It is the RF input cable (from either the community
cable distro system, or from the TVRO antenna).

There's only ONE of those hence no possibility of a LOOP !

Good. We'll remember that next time someone comes
here asking about their HT system hum problem, and
why it goes away when they disconnect the cable. We
will let you explain to them that the hum is only in
their imagination.

Who said anything about it being in their imagination ?

Graham

[Eeyore]

Chris Hornbeck wrote:

"Richard Crowley" wrote:
"Eeyore" wrote ...

It is not the mains power that is earthed/grounded.
It is the RF input cable (from either the community
cable distro system, or from the TVRO antenna).

There's only ONE of those hence no possibility of a LOOP !

Good. We'll remember that next time someone comes
here asking about their HT system hum problem, and
why it goes away when they disconnect the cable. We
will let you explain to them that the hum is only in
their imagination.

This kinda thing is a large part of my day-gig these
last coupla years. I used to give the information away
free to our "installer guys" and now I get paid
(peanuts) to fix these issues myself. It's what in
America is called "early retirement". Arf .

Ground loops *do not* require a perfect non-conductive
loop to matter.

I assume you actually mean condcutive.


Just the opposite, in fact. Modern consumer
electronics has many amazingly diverse sources of ground
contamination, and all include some element of current
into a "nominal" ground.

IOW, there are no "grounds". The difference between our
preconceptions of "ground" and the reality are the crux
of the biscuit.

Ground loops are systemic and subtle, and include the
summed parasitic couplings from all devices' mains to
each device's nominal Earth. It's a non-trivial summation.

What do you mean by 'nominal earth' ?

What you haven't mentioned and it's far more insidious is the effect of
the Y filter caps in switched mode power supplies that create a leakage
current to ground if you attempt to supply a mains ground to a system
incorporating such a device. This is the usual source of 'hum' when
connecting laptops to audio sysyems when using their mains adaptors
(whether 2 or 3 wire).

Graham

[Kevin McMurtrie]

In article ,
"Arny Krueger" wrote:

"Eeyore" wrote in
message

Balanced wiring only gives you an advantage if the
equipment is balanced. With clever wiring it's only
actually necessary for either the 'sending' or
'receiving' equipment to have a balanced input or ouput
but you need to know what you're doing in this case.

I know the strong advantage that balanced inputs give, but what advantage do
you get from an electronically-balanced output driving an unbalanced input?

The output signal doesn't have to be driven on both lines. What helps
is having the output signal relative to the other line. It eliminates
ground loop current from about an inch of wire on the PCB. The ground
current can instead flow entirely along non-signal shield wiring.

A Mackie and Xenyx mixer show logical schematics where the output stage
tip is driven relative to the ring, which is grounded by a resistor to
the shield. I haven't traced the PCB to see how true that holds in the
physical schematics.

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[Kevin McMurtrie]

In article CL-dnffVt5DGNpnVnZ2dnUVZ_oSunZ2d@pcez,
"Richard Crowley" wrote:

"Kevin McMurtrie" wrote ...
$15 for Cat6 and $20 left over for balancing transformers?
I don't think that would work well.

Actually, growing numbers of people find it ideal.

He gave links to balanced wiring. Balanced audio allows for a bit of
a
grounding mismatch between equipment. If his equipment supports it,
balanced wiring is by far the cheapest and highest quality way to do
this.

1) The OP was asking about wiring his consumer audio
equipment. The likelyhood that it has balanced inputs or
outputs lies somewhere between slim and none.

2) Cat5 (et.al.) *IS* balanced. In fact, it is balanced much
better than most any cable sold for audio purposes.

Sometimes only the green and orange pairs used for 10/100 Ethernet are
balanced in Cat 5. You don't know until you strip away a foot of the
jacket.

Cat 5e, 6, and anything else supporting 1000Base-T Ethernet have four
pairs that are well balanced. Cat 6 has a "+" shaped spine to reduce
the chance of crosstalk between pairs.

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[Serge Auckland[_2_]]

"Eeyore" wrote in message
...


Serge Auckland wrote:

"Eeyore" wrote
Serge Auckland wrote:

To paraphrase I think, John Linsley Hood, you can always cut down on
safety margins if you have complete control over circumstances.

There is NOTHING unsafe about Class II equipment. In fact it has to be
intrinsicly SAFER than earthed kit.


In your case, anyone making an equipment change at some stage in the
future could set up a hum-loop.

COULD ? Why WOULD they.

You're inventing fictional problems again.


Not so much a case of inventing fictitional problems, just good
engineering
practice. Whenever I implement any solution to a problem, I try and think
of
what could possibly go wrong in the future and try to plan for it.

All very well but if you introduce a hum loop you can add transformers
THEN !
They're simply not NEEDED here !


If you're sure there won't be any future changes, and you're only trying
to
avoid hum
loops, then your solution is probably fine.

It will be.


That, by the way, is what I
meant in paraphrasing J L-H. I wasn't suggesting your solution is unsafe,
just that if you solve a problem in the minimum way possible, you
sacrifice
the flexibility of a better solution.

Interesting that your AV equipment is all ungrounded. Mine isn't. Some
items
are ungrounded - DTTV box, DVD player, DVD recorder, but the main TV is
grounded, my CD player, pre-amp, and active 'speakers are all grounded.
Turntables are all grounded. It's a mixture, so your solution isn't
generally applicable.

A turntable does not need to be physically GROUNDED. Just connect its
chassis to
the chassis of the amplifier with the cartridge preamp.

I haven't seen a TV with a ground conductor since just about forever btw.

Graham



In my case, two of my turntables (EMT 948 and AEG TRS9000) have built-in
electronics (both audio and control) and require a ground at least for
safety. There is a separate ground-lift facility to float the audio ground
from safety ground, and/or to connect the audio ground to Technical Ground,
separate again from safety ground. The outputs are transformer balanced,
fully floating. My other two turntables are conventionally grounded through
the pre-amp, which in my case has a ground.

As to the TV, it is a Sony Plasma, and definitely has a safety ground
connected to the rear metalwork.

Your earlier comment about laptop power supplies is spot-on. I've recently
had a lot of trouble curing a hum from my laptop which was only apparent
when connecting to my unbalanced hi-fi, but was completely absent when using
a balanced connection. (The sound card is a Digigram VXPocket, which has
balanced ins and outs). I finally solved the problem by finding a power
supply that didn't cause the hum, presumably because this one has a
different arrangement of capacitors. It also has only a 2 wire input whereas
the original supply had a three-wire mains input.

S.


--
http://audiopages.googlepages.com

[dizzy]

Eeyore wrote:

I haven't seen a TV with a ground conductor since just about forever btw.

? My new Samsung LCD TV must be an oddball, then...

[Richard Crowley]

"dizzy" wrote ...
Eeyore wrote:
I haven't seen a TV with a ground conductor since just about forever btw.

? My new Samsung LCD TV must be an oddball, then...

Remember that Graham is in the UK.
Do they sell appliances with mains plugs attached?
Or do buyers still have to install their own?

[Chris Hornbeck]

On Wed, 16 Apr 2008 07:06:36 +0100, Eeyore
wrote:

Ground loops are systemic and subtle, and include the
summed parasitic couplings from all devices' mains to
each device's nominal Earth. It's a non-trivial summation.

What do you mean by 'nominal earth' ?

Earth ground is an abstraction and all other "grounds" are
local and to some degree contaminated. If there's a better
term, I'll use it, but haven't heard it (yet).

What you haven't mentioned and it's far more insidious is the effect of
the Y filter caps in switched mode power supplies that create a leakage
current to ground if you attempt to supply a mains ground to a system
incorporating such a device. This is the usual source of 'hum' when
connecting laptops to audio sysyems when using their mains adaptors
(whether 2 or 3 wire).

That's an excellent example. Local nominal ground is
contaminated by local garbage and causes a systemic
problem.

Much thanks, as always,

Chris Hornbeck

[Chris Hornbeck]

On Wed, 16 Apr 2008 06:56:31 +0100, Eeyore
wrote:

I haven't seen a TV with a ground conductor since just about forever btw.

In the US, essentially *all* the fancy modern TVs have safety
grounds ("third wire") but our Edison is different than
y'all's.

Much thanks, as always,

Chris Hornbeck

[Eeyore]

dizzy wrote:

Eeyore wrote:

I haven't seen a TV with a ground conductor since just about forever btw.

? My new Samsung LCD TV must be an oddball, then...

It may be that LCD TVs are different. Probably that damn switchmode power
supply and the need to install filter caps to ground to meet FCC/CE EMI regs
etc.

Graham

[Eeyore]

Richard Crowley wrote:

"dizzy" wrote ...
Eeyore wrote:
I haven't seen a TV with a ground conductor since just about forever btw.

? My new Samsung LCD TV must be an oddball, then...

Remember that Graham is in the UK.
Do they sell appliances with mains plugs attached?

For several decades or so.

Graham

[Tomi Holger Engdahl[_2_]]

Kevin McMurtrie writes:

In article CL-dnffVt5DGNpnVnZ2dnUVZ_oSunZ2d@pcez,
"Richard Crowley" wrote:

"Kevin McMurtrie" wrote ...
$15 for Cat6 and $20 left over for balancing transformers?
I don't think that would work well.

Actually, growing numbers of people find it ideal.

He gave links to balanced wiring. Balanced audio allows for a bit of
a
grounding mismatch between equipment. If his equipment supports it,
balanced wiring is by far the cheapest and highest quality way to do
this.

1) The OP was asking about wiring his consumer audio
equipment. The likelyhood that it has balanced inputs or
outputs lies somewhere between slim and none.

2) Cat5 (et.al.) *IS* balanced. In fact, it is balanced much
better than most any cable sold for audio purposes.

Sometimes only the green and orange pairs used for 10/100 Ethernet are
balanced in Cat 5. You don't know until you strip away a foot of the
jacket.

Where have you seen such cable ?

All the CAT5 cables I have seen consists of four well balanced
wire pairs. There are four well built twisted pairs on CAT5 wire.
And the twist rates used on different pairs are intentionally
different to reduce the crosstalk.

Cat 5e, 6, and anything else supporting 1000Base-T Ethernet have four
pairs that are well balanced. Cat 6 has a "+" shaped spine to reduce
the chance of crosstalk between pairs.

--
Block Google's spam and enjoy Usenet again.
Reply with Google and I won't hear from you.

--
Tomi Engdahl (http://www.iki.fi/then/)
Take a look at my electronics web links and documents at
http://www.epanorama.net/

[Serge Auckland[_2_]]

"Eeyore" wrote in message
...


dizzy wrote:

Eeyore wrote:

I haven't seen a TV with a ground conductor since just about forever
btw.

? My new Samsung LCD TV must be an oddball, then...

It may be that LCD TVs are different. Probably that damn switchmode power
supply and the need to install filter caps to ground to meet FCC/CE EMI
regs
etc.

Graham



Not just LCD TVs. My Plasma TV has a third wire, as does the small LCD in
the kitchen, as does the LCD monitor on my audio computer. It's this last
one that's caused me a lot of problems lately, as it's the only part of the
audio system (computer (a screen-less laptop), external hard-drive and
screen) that's grounded.

S.

--
http://audiopages.googlepages.com

[Eeyore]

Serge Auckland wrote:

"Eeyore" wrote
dizzy wrote:
Eeyore wrote:

I haven't seen a TV with a ground conductor since just about forever
btw.

? My new Samsung LCD TV must be an oddball, then...

It may be that LCD TVs are different. Probably that damn switchmode power
supply and the need to install filter caps to ground to meet FCC/CE EMI
regs etc.


Not just LCD TVs. My Plasma TV has a third wire, as does the small LCD in
the kitchen, as does the LCD monitor on my audio computer. It's this last
one that's caused me a lot of problems lately, as it's the only part of the
audio system (computer (a screen-less laptop), external hard-drive and
screen) that's grounded.

I fully expect thay all have switchmode PSUs.

Graham

[Kevin McMurtrie]

In article ,
Tomi Holger Engdahl wrote:

Kevin McMurtrie writes:

In article CL-dnffVt5DGNpnVnZ2dnUVZ_oSunZ2d@pcez,
"Richard Crowley" wrote:

"Kevin McMurtrie" wrote ...
$15 for Cat6 and $20 left over for balancing transformers?
I don't think that would work well.

Actually, growing numbers of people find it ideal.

He gave links to balanced wiring. Balanced audio allows for a bit of
a
grounding mismatch between equipment. If his equipment supports it,
balanced wiring is by far the cheapest and highest quality way to do
this.

1) The OP was asking about wiring his consumer audio
equipment. The likelyhood that it has balanced inputs or
outputs lies somewhere between slim and none.

2) Cat5 (et.al.) *IS* balanced. In fact, it is balanced much
better than most any cable sold for audio purposes.

Sometimes only the green and orange pairs used for 10/100 Ethernet are
balanced in Cat 5. You don't know until you strip away a foot of the
jacket.

Where have you seen such cable ?

Some bulk wire at work that was used to make patch cables. All four
pairs are twisted but the two that are unused in 10/100 have a very low
twist quality. From the ones I opened, it varied from 1 to 10 turns per
foot.


All the CAT5 cables I have seen consists of four well balanced
wire pairs. There are four well built twisted pairs on CAT5 wire.
And the twist rates used on different pairs are intentionally
different to reduce the crosstalk.

Cat 5e, 6, and anything else supporting 1000Base-T Ethernet have four
pairs that are well balanced. Cat 6 has a "+" shaped spine to reduce
the chance of crosstalk between pairs.

--
Block Google's spam and enjoy Usenet again.
Reply with Google and I won't hear from you.

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