[OJNeg]

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Just to clarify a few things.
 
First, a rod stuck in the dirt (i.e. earth ground) has absolutely no relevance whatsoever to an audio system with respect go "ground." The rod stuck in the dirt is only there for lightning protection.
 
Second, the third pin on the AC power cord also has absolutely no relevance whatsoever to an audio system with respect to "ground" other than being the leading cause of ground loop problems.
 
The third pin is there purely for safety purposes. It's tied to neutral back at the service panel and provides a return path for fault currents in the event that a failure should cause AC hot to contact the equipment chassis. This prevents you from being the return path and getting electrocuted. Sadly, it's not terribly difficult to design equipment chassis to meet Class II specs (i.e. "double insulated") in which case the third pin is not required. However these things get slapped onto everything, even equipment which does meet Class II specs. For some reason, people have come to believe that equipment with a 3 pin IEC 320 receptacle on the back is a sign of "quality." But as I said previously, outside of safety purposes, all it does is create ground loop problems.
 
The only "ground" that is relevant is the equipment's own internal ground.
 
se

 
So where do ground loop problems arise from exactly? If I have multiple audio components that are all using 3 pin IEC connectors, then they're all sharing a common ground back at the switch box, correct?

 

[Steve Eddy]

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So where do ground loop problems arise from exactly? If I have multiple audio components that are all using 3 pin IEC connectors, then they're all sharing a common ground back at the switch box, correct?

 
Ground loops arise largely from interchassis leakage currents, namely the capacitive coupling between the AC hot lead and the AC safety ground lead. As per Ohm's Law, these currents create voltage drops across the resistances of the power cords, contacts, and AC wiring in the walls. Some designers will try and isolate the amplifier's signal reference ground from the chassis (according to code, the AC safety ground needs to tie to the equipment chassis) using a variety of means such as resistors, capacitors, or diodes. Some designers don't and tie the amplifier's signal reference ground directly to the chassis.
 
se

 

[jcx]

getting a bit far from "balanced headphones"
 
protective earth/safety gnd wire can pick up low levels of AC from induction as it runs along side the power wiring
 
a house wiring tweak is to twist the power wire pairs before pulling to cut down the induction to the safety gnd wire
 
power cords, extensions don't do this right - if twisted, all 3 conductors are usually twisted together
 
 
with lots of pieces of equipment plugged in the individual allowed leakage currents can add up, the leakage current can give additional V in the safety gnd wire - a light industrial building I worked in had 2 outlets within a few feet of each other on adjacent walls with ~3 V AC between safety gnds, they were on different branch circuits - had over a  hundred feet of wire between the safety gnds common connection back at the panel
 
 
best situation: headphone rigs can usually power all components from the same outlet, power strip  - problems could start when the different parts of the system are plugged into sockets on opposite walls
 
with line level sources, good heavy braid/shield RCA cabling, only one 3-wire safety gnded piece in the rig, rest 2-wire, floating, all powered from one outlet there shouldn't be any need for balanced interconnect in home audio

 

[maxmays1]

^ Right ^

 

[Steve Eddy]

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with line level sources, good heavy braid/shield RCA cabling, only one 3-wire safety gnded piece in the rig...

 
Or better still, none.

 
se

 

[qusp]

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Too bad "ground" is such an entrenched part of the terminology.  Maybe we'd be better off if everybody just called it something else in situations where earth ground is not meant, like the 0-reference.

 
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Amen!
 
se

 
Quote:

 
Ground loops arise largely from interchassis leakage currents, namely the capacitive coupling between the AC hot lead and the AC safety ground lead. As per Ohm's Law, these currents create voltage drops across the resistances of the power cords, contacts, and AC wiring in the walls. Some designers will try and isolate the amplifier's signal reference ground from the chassis (according to code, the AC safety ground needs to tie to the equipment chassis) using a variety of means such as resistors, capacitors, or diodes. Some designers don't and tie the amplifier's signal reference ground directly to the chassis.
 
se

indeed, I hate having to use it so people 'understand'
 
who is using ground and negative interchangeably so I can correct them...all? now with headphones or other floating transducers they couldnt give a stuff what you call it.
 
of course loops happen on a smaller scale in the drop across ground planes as well

 

[Chris J]

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who is using ground and negative interchangeably so I can correct them...all?
 

 
In mobile applications (e.g. cars, trucks, etc.) the battery negative terminal is tied to the truck or car frame.
Since frame is considered ground, the logic goes negative must be ground.
Plays hell in the Telecom field.
In Telecom, the system is a 48 Vdc system (which is backed up by a 48 Vdc battery string), the positive of this system is grounded.(i.e or bonded to earth).
 
The problem in Telecom is that some people would designate the RED lead off the battery string as positive, so the RED lead is ground?
Some people would say, no the red lead is the live wire, so the RED lead must be negative.   We decidied to not use RED power cables, just use black cables marked +ve and -ve.
 
How off topic am I now?
 
BT, never cut the third pin off an AC cable to solve ground loop problems unless you want to void the Regulatory Approval: UL, CSA, TUV, etc. i.e compromise the safety of your equipment.

 

[qusp]

thats not really the same thing though is it? in the first case ground and the negative terminal are connected, so are the same potential at least, but it doesnt mean they are the same thing. surely the frame would be equivalent to chassis ground?
 
seems like both are just atrocities created from insufficiently defined conventions
 
best way to solve a ground loop problem is to not create one in the first place, I like having the 3rd prong on AC

 

[maxmays1]

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thats not really the same thing though is it? in the first case ground and the negative terminal are connected, so are the same potential at least, but it doesnt mean they are the same thing. surely the frame would be equivalent to chassis ground?
 

Correct. It's an improper practice but the negative terminal of a battery is termed as ground in most mobile applications, or the use of DC power, and or positive charged batteries(As it is rare you will find negative charged batteries). But in this case it kind of makes sense because on most batteries the negative plating does not send a charge but instead receives, so it acts like a ground, or what is sometimes referred to as "return line".

 

[qusp]

the negative terminal, just like 'ground' is simply a reference that can be either negative or relatively positive depending on what it is being referred to. a negative 'charge' is sourced not sent, depending on how negative it is, is it not? In the case of several batteries connected in series, it can easily be treated as a positive terminal for part of the circuit, its a 2 terminal device, all charges are relative. a ground terminal can also be positive with reference to the right thing, its all relative.
 
calling it ground is simply incorrect, maybe common, but incorrect all the same. it could only be called that provided there is no negative going supply rail like those with center tapped battery supplies, otherwise it would be also dangerous

 

[Steve Eddy]

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best way to solve a ground loop problem is to not create one in the first place, I like having the 3rd prong on AC

 
I agree that the best way to solve a ground loop problem is not to create one in the first place. So why would you want to have a third prong on the AC, which is the leading cause of ground loops?

 
se

 

[Chris J]

Quote:

thats not really the same thing though is it? in the first case ground and the negative terminal are connected, so are the same potential at least, but it doesnt mean they are the same thing. surely the frame would be equivalent to chassis ground?
 
seems like both are just atrocities created from insufficiently defined conventions
 
best way to solve a ground loop problem is to not create one in the first place, I like having the 3rd prong on AC

 
I was just pointing out some of the confusion I have seen in Telecom.

Red is live wire or Red is positive? etc.
 
Sure, frame is equivalent to chassis ground.
 
3rd prong is nice:
you can bond the chassis to earth ground for:
safety
AC noise filtering
chassis shielding
use a shielded AC cable
this does not you need to bond the audio (signal) ground to earth  
 
 
Quote:

Correct. It's an improper practice but the negative terminal of a battery is termed as ground in most mobile applications, or the use of DC power, and or positive charged batteries(As it is rare you will find negative charged batteries). But in this case it kind of makes sense because on most batteries the negative plating does not send a charge but instead receives, so it acts like a ground, or what is sometimes referred to as "return line".

 
Sure.
Other than Telecom, I am not aware of any positively grounded battery strings.
Often battery strings are loosley coupled to ground
 
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the negative terminal, just like 'ground' is simply a reference that can be either negative or relatively positive depending on what it is being referred to. a negative 'charge' is sourced not sent, depending on how negative it is, is it not? In the case of several batteries connected in series, it can easily be treated as a positive terminal for part of the circuit, its a 2 terminal device, all charges are relative. a ground terminal can also be positive with reference to the right thing, its all relative.
 
calling it ground is simply incorrect, maybe common, but incorrect all the same. it could only be called that provided there is no negative going supply rail like those with center tapped battery supplies, otherwise it would be also dangerous

 
Sorry mate, your (statement?) question? is confusing my little pea brain.
A battery has two terminals: one is always positive, the other is always negative.
In a battery string you could argue that it is all relative....negative WRT what?
 
You could argue that it should oly be called Ground if that buss is bonded to earth.
A power supply can be three terminal:   positve, common and negative, for example, the power supply in a power amp or preamp.
If common is bonded to earth, then you could say it is grounded.

 

[Steve Eddy]

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3rd prong is nice:
you can bond the chassis to earth ground for:
safety

 
It's not its being tied to earth ground that provides the safety. It's its being tied to AC neutral that provides the safety. That's what provides the return for fault currents.
 
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AC noise filtering

 
How does it being tied to earth ground provide any AC noise filtering?
 
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chassis shielding

 
How does it being tied to earth ground provide any chassis shielding? The chassis already is a shield. Doesn't need to be tied to earth ground for that.
 
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use a shielded AC cable

 
Don't need any connection to earth ground for that. Just a connection of the AC cable's shield to the chassis.
 
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this does not you need to bond the audio (signal) ground to earth

 
Was there supposed to be another word in that sentence?
 
se

 

[kevin gilmore]

The problem with AC neutral is that you can't be guaranteed that the house is wired
correctly, or that someone is using a cheater plug, and has it plugged in backwards.
Or other high power loads that can lift neutral several volts.
 
Outside the USA where 220v or 240v is standard, there is no neutral. Only safety
ground.
 
The safest solution is to ground the chassis and then double insulate the power
supply.

 

[maxmays1]

Quote:

 
How does it being tied to earth ground provide any chassis shielding? The chassis already is a shield. Doesn't need to be tied to earth ground for that.

sometimes you have large amounts of ground(negative) connections attached to the chassis . any external power surge that comes in contact with your chassis can disrupt or damage your components but mostly your battery. This shield or even a anode>cathode design will draw power away from your negative line. 
 
Most sports cars use the base plates as both the (the base plate) and chassis shield so external power wont disrupt there battery.In these situations the chassis itself is not used as a negative return line because all power connection are attached directly to the battery and not run through the chassis. atleast this is the practice for very serious racing leagues. some high end audio system fabricators use this method as well.