Taking care of grounding

Cutting off the grounds definitely works, but IF you have an electrical problem with a component the ground is your safety factor.

With the many different meanings of the word 'ground' it's hard to tell just what task they claim to do better.

Purite Audio said:

Lifting earth wires is a really stupid thing to do, potentially dangerous and if there is a fire you will have invalidated your house insurance.
Keith.

Click to expand...

For sure! Disconnecting (or re-routing) the Safety Ground/Protective Earth conductor is very stupid.

Audio equipment does not 'like' to be grounded as the potential (if you will pardon the pun ) exists for ground loops.

If its not grounded though, the dangers can be profound; not only that but export to other countries can be a real problem if you are a manufacturer.

It turns out though that equipment can be grounded and not ground-looped at the same time and if this is properly done, will perform better in such a way that no grounding system will bring any further improvement. The only reason such systems exist at all is because grounding is so poorly understood by designers in high end audio. Too many are hobbyists without degrees...

The chassis should be hard-grounded to the ground connection at the wall, plain and simple. The audio circuitry within the chassis should not, but should be referenced by some means to chassis ground. If this is done properly, the result will be lower noise and smoother sound as ground loops can cause intermodulations and the chassis can then do its job of shielding. This is the big result many people get when using grounding systems, but if their equipment was properly grounded in the first place it would sound even better (and the add-on grounding systems would have no effect or actually be detrimental).

Its my opinion that add-on grounding systems are fixing a problem that the manufacturer of the preamp, amp or whatever should have got right in the first place. This stuff has been known for decades... sorry for the crumudgenly comments, but that's the way it is...

Atmasphere said:

Audio equipment does not 'like' to be grounded as the potential (if you will pardon the pun ) exists for ground loops.

If its not grounded though, the dangers can be profound; not only that but export to other countries can be a real problem if you are a manufacturer.

It turns out though that equipment can be grounded and not ground-looped at the same time and if this is properly done, will perform better in such a way that no grounding system will bring any further improvement. The only reason such systems exist at all is because grounding is so poorly understood by designers in high end audio. Too many are hobbyists without degrees...

The chassis should be hard-grounded to the ground connection at the wall, plain and simple. The audio circuitry within the chassis should not, but should be referenced by some means to chassis ground. If this is done properly, the result will be lower noise and smoother sound as ground loops can cause intermodulations and the chassis can then do its job of shielding. This is the big result many people get when using grounding systems, but if their equipment was properly grounded in the first place it would sound even better (and the add-on grounding systems would have no effect or actually be detrimental).

Its my opinion that add-on grounding systems are fixing a problem that the manufacturer of the preamp, amp or whatever should have got right in the first place. This stuff has been known for decades... sorry for the crumudgenly comments, but that's the way it is...

Click to expand...

Good post .

In regards AC grounding I believe there have been some misconceptions brought forth.

In my AC system in my house in Dallas (and in all others I have inspected) the "earth ground wire", which in commercial residential "Romex" (most used form of AC wiring) is a bare copper wire (with a loosely wrapped paper shield on it) ACTUALLY IS TIED TO THE AC RETURN LINE AT THE DISTRIBUTION BOX. To verify this all one has to do is remove the box cover (very, very, very dangerous - do not do this if you are not experienced - ask a qualified electrician to do this).

This, at least to my understanding means that if you tie your chassis to "earth ground" and your signal processing circuitry to AC "return" you have created the very situation that a ground loop requires - you have two different paths to the same ground. Therefore any differing potentials on these "grounds" could (and probably will) cause noise in your circuitry (as the signal processing parts are seeing a different ground than the chassis itself).

I really do NOT know the correct way to "ground" stereo equipment. Tie the AC return line to the earth ground? Done that and did not see any problems with the stereo signal. I have been inside of amplifiers that DID tie the chassis to "earth ground" and the signal processing to AC return (as it has to be). This is a very interesting question - and the resolution is rather unclear. For myself both get tied together - AC return and earth ground. Such seems to work - for certain they are tied together at the distribution point so my thinking was to move "uphill" from any potential differences brought on by varying distances/routes from the same point.

No circuit uses "signal processing circuitry to AC "return" "; this would be considered to be unsafe. This was a practice decades ago when 'AC/DC' radios were still legal.

The proper way to ground audio equipment:

1) chassis ties to AC ground (middle prong on USA AC outlets, green wire)
2) circuit 'floats' at ground potential, being referenced to chassis at all times through some device (likely a resistor) of such value that ground loop currents cannot form.

If this is done, there is no need to place a stake in the garden or the like for additional grounding. The AC ground (which should be at earth potential anyway; if not, contact an electrician) will be quite sufficient.

Any deviation from this plan: you will get more noise, and 'grounding systems' may well seem to improve things, but they will never get things to be as good as they would be if the equipment was properly designed in the first place. It really is that simple.

valkyrie said:

In regards AC grounding I believe there have been some misconceptions brought forth.

In my AC system in my house in Dallas (and in all others I have inspected) the "earth ground wire", which in commercial residential "Romex" (most used form of AC wiring) is a bare copper wire (with a loosely wrapped paper shield on it) ACTUALLY IS TIED TO THE AC RETURN LINE AT THE DISTRIBUTION BOX. To verify this all one has to do is remove the box cover (very, very, very dangerous - do not do this if you are not experienced - ask a qualified electrician to do this).

Click to expand...

This is correct.

This, at least to my understanding means that if you tie your chassis to "earth ground" and your signal processing circuitry to AC "return" you have created the very situation that a ground loop requires - you have two different paths to the same ground. Therefore any differing potentials on these "grounds" could (and probably will) cause noise in your circuitry (as the signal processing parts are seeing a different ground than the chassis itself).

Click to expand...

This is not correct .

The earth ground, the third pin in your AC cord and chassis of the equipment (if not double insulated) must at all times be connected to earth ground for safety. No ground loop is created because of this (not directly) and as such, should never be defeated.

Think of audio equipment in your car. It has no "ground" connection yet it can either work correctly or have ground loop. So the earth ground does not play a role here.

The problem is the shield resistance of the audio interconnect between two equipment and leakage current. The shield resistance times the leakage current results in a voltage drop. That voltage difference is what causes the hum/noise. The leakage current is a function of the design of your equipment. No matter what you do with outlets and such, the leakage current can still be there. Here is a nice set of calculations by Bill Whitlock:

An Overview of Audio System Grounding & Interfacing 9/4/2012
Bill Whitlock

Leakage Current Effect - A Calculated Example

• A 25-foot cable (foil shield, #26 AWG drain wire) has an end-to-end shield resistance of 1 ?

• Measured leakage current between the ungrounded devices is 316?A (well under the UL limit of 750 ?A)

• From Ohm’s law, noise voltage E = I x R = 316 ?A x 1 ? = 316 ?V

• Consumer ?10 dBV reference level = 316 mV

• Signal to Noise ratio = 20 x log (316 mV?316 ?V) = 60 dB

• This is 35 dB worse than an audio CD!

• Same length of Belden #8241F cable, with its shield resistance of only 0.065 ?, makes S?N 84 dB, an improvement of 24 dB!

From a noise perspective, shield resistance is the most important parameter of all.
How many times have you seen it specified on a data sheet or in advertising hype?
I rest my case about clueless manufacturers!


So the solution is to use balanced interconnects whenever you can. If you have to use unbalanced, get a cable with the thickers/lowest resistance shield. If nothing works, a transformer from good manufacturer like Jensen can solve the problem but obviously won't be 100% transparent.

I really do NOT know the correct way to "ground" stereo equipment. Tie the AC return line to the earth ground? Done that and did not see any problems with the stereo signal. I have been inside of amplifiers that DID tie the chassis to "earth ground" and the signal processing to AC return (as it has to be). This is a very interesting question - and the resolution is rather unclear. For myself both get tied together - AC return and earth ground. Such seems to work - for certain they are tied together at the distribution point so my thinking was to move "uphill" from any potential differences brought on by varying distances/routes from the same point.

Click to expand...

It is so tempting to think of this as a ground wire problem but it just isn't. As you say, it all depends on how the internal design of the product is. That determines the leakage current.

Sorry guys - but what has been stated by Amir and Atmasphere, whom I respect greatly, does not quite square up with my perception (experience) or education (extensive including an MS degree). Earth ground (or the "third prong") is in reality tied to the AC return line (the white insulated wire in Romex) at the distribution box (which is some resistance away from the point of use - and that resistance should be IDENTICAL to the AC return line).

Currents do form on the AC return - how do you think GFI (Ground Fault Interrupters) work? They sense voltages on the ground plane (and ground is only rarely at zero potential - most particularly when NOTHING is consuming AC - under heavy use, i.e. large currents being passed - AND RETURNED - voltages are on the ground plane).

The "earth ground" did two things. It force the polarity of an AC plug to only be in one arrangement (thus keeping people from using AC devices wherein the "hot" was on the "shell" of the device) AND it helped to keep voltages from forming on the ground plane (AC return) by adding a separate ground line (a lot of AC devices WILL WORK WITHOUT AN AC RETURN LINE BEING PRESENT - very dangerous as the path of return is now, literally into the 'ground' (as in the dirt, the real geological earth).

SO; while I am not so sure how this AC return (ground) phenomena vis a vi an audio device should be best handled, the responses thus far do not relate to any reality that I am aware of.

Atmasphere's "floating" circuit makes about zero sense - if the "earth ground" is tied to the AC return nothing should be floating - unless of course voltages are forming on the AC return - and in that case you have a ground loop (lets define that as two different electrical paths to ground that can experience a voltage differential between them).

As for Amir's "balanced interconnects" (which I use with my Pass amp to preamp as both are BALANCED INTERNALLY)such is about CMRR (Common Mode Rejection Ratio) and has about ZERO to do with the problem at hand). This issue as I understand it is in discussing how the two ground wires present in a domestic AC system should be connected to a "quality" audio device.

I just tie them together at the point of use. Seems to work as all I am doing is doubling the return line.

The complete, easy to read (it's mostly pictures) Bill Whitlock paper:

"An Overview of Audio System Grounding and Interfacing"
by Bill Whitlock, President
Jensen Transformers, Inc.
Life Fellow, Audio Engineering Society
Life Senior Member, Institute of Electrical & Electronic Engineers

is available at:
http://centralindianaaes.files.wordpress.com/2012/09/indy-aes-2012-seminar-w-notes-v1-0.pdf

******************************
other miscellaneous points:

a] Romex® ground is a bare copper wire (with a loosely wrapped paper shield on it)
It's not a shield it's an insulator or sheath.

b] The 3rd wire - Safety Ground/Protective Earth connects to the power company Neutral at the service entrance/main circuit breaker box.

c] The stake in the dirt connects to the power company Neutral at the service entrance/main circuit breaker box. This is the only point that any and all stakes should connect. It is a common mis-understanding is many electrical fields that this connection aids AC power quality. This is incorrect, it's only there for safety.

d] Another common mis-understanding is that a GFCI requires a Safety Ground connection or reference. A GFCI only requires Hot & Neutral connections. They are often used in older 2 wire AC power systems.

valkyrie said:

Sorry guys - but what has been stated by Amir and Atmasphere, whom I respect greatly, does not quite square up with my perception (experience) or education (extensive including an MS degree). Earth ground (or the "third prong") is in reality tied to the AC return line (the white insulated wire in Romex) at the distribution box (which is some resistance away from the point of use - and that resistance should be IDENTICAL to the AC return line).

Currents do form on the AC return - how do you think GFI (Ground Fault Interrupters) work? They sense voltages on the ground plane (and ground is only rarely at zero potential - most particularly when NOTHING is consuming AC - under heavy use, i.e. large currents being passed - AND RETURNED - voltages are on the ground plane).

The "earth ground" did two things. It force the polarity of an AC plug to only be in one arrangement (thus keeping people from using AC devices wherein the "hot" was on the "shell" of the device) AND it helped to keep voltages from forming on the ground plane (AC return) by adding a separate ground line (a lot of AC devices WILL WORK WITHOUT AN AC RETURN LINE BEING PRESENT - very dangerous as the path of return is now, literally into the 'ground' (as in the dirt, the real geological earth).

SO; while I am not so sure how this AC return (ground) phenomena vis a vi an audio device should be best handled, the responses thus far do not relate to any reality that I am aware of.

Atmasphere's "floating" circuit makes about zero sense - if the "earth ground" is tied to the AC return nothing should be floating - unless of course voltages are forming on the AC return - and in that case you have a ground loop (lets define that as two different electrical paths to ground that can experience a voltage differential between them).

As for Amir's "balanced interconnects" (which I use with my Pass amp to preamp as both are BALANCED INTERNALLY)such is about CMRR (Common Mode Rejection Ratio) and has about ZERO to do with the problem at hand). This issue as I understand it is in discussing how the two ground wires present in a domestic AC system should be connected to a "quality" audio device.

I just tie them together at the point of use. Seems to work as all I am doing is doubling the return line.

Click to expand...

It sounds to me like you did not understand what I posted. The 'floating' concept is not as you describe but instead like I described. The idea is simply that the chassis and circuit ground are not the same thing, as the chassis has to be electrically grounded. You might want to go back and read my first post on this thread. In order to get UL and CE approval, the chassis must be grounded. However if the audio circuit is directly grounded to the chassis, it will be susceptible to ground loops. The means I suggested fixes that, and allows the circuit to still meet UL requirements and also meet EU Directives (CE Mark).

I do not recommend having a second 'ground' such as a stake in the yard (to be clear, one to which an audiophile is making direct connections). It is not needed if the electronics are properly grounded. It may well be very "helpful" if there are design flaws in the circuitry!

This should have nothing to do with the AC return- of course there are currents there- and substantial ones at that as anything on the hot side will be on the neutral side as well, according to Mr. Kirchoff...

Yes, the green wire and white (neutral) tie together at the breaker box. http://en.wikipedia.org/wiki/Electrical_wiring However the white wire contains AC return currents and the green wire does not. If the green wire *does* have substantial currents, ground leakage is present in the equipment hooked up which is generally not a good thing.

If you look at equipment that does not have ground loop problems, it is generally set up in the manner I described, or else the chassis is not grounded at all.

valkyrie said:

Sorry guys - but what has been stated by Amir and Atmasphere, whom I respect greatly, does not quite square up with my perception (experience) or education (extensive including an MS degree). Earth ground (or the "third prong") is in reality tied to the AC return line (the white insulated wire in Romex) at the distribution box (which is some resistance away from the point of use - and that resistance should be IDENTICAL to the AC return line).

Click to expand...

That is true. And its only purpose is for safety. It is a redundant path back to the panel to stop shorts of the hot to unit chassis.

Currents do form on the AC return - how do you think GFI (Ground Fault Interrupters) work? They sense voltages on the ground plane (and ground is only rarely at zero potential - most particularly when NOTHING is consuming AC - under heavy use, i.e. large currents being passed - AND RETURNED - voltages are on the ground plane).

Click to expand...

As was just noted, GFCI does not have any need for ground wire. It works on the principle of having no current differential between the hot and neutral lines. What goes out must come back. Should 5 milliamp or more of it be siphoned off through your body to the ground, it will trip and open the load. Here is a picture showing that:



There is no sourcing of voltages or anything like that with respect to ground plane which does not exist. And again, it is a safety issue unrelated to the topic at hand.

The "earth ground" did two things. It force the polarity of an AC plug to only be in one arrangement (thus keeping people from using AC devices wherein the "hot" was on the "shell" of the device) AND it helped to keep voltages from forming on the ground plane (AC return) by adding a separate ground line (a lot of AC devices WILL WORK WITHOUT AN AC RETURN LINE BEING PRESENT - very dangerous as the path of return is now, literally into the 'ground' (as in the dirt, the real geological earth).

Click to expand...

The earth ground's purpose is to provide safety at the panel. Surges on the neutral line are routed to the ground. It is not a topic related to this discussion.

As for Amir's "balanced interconnects" (which I use with my Pass amp to preamp as both are BALANCED INTERNALLY)such is about CMRR (Common Mode Rejection Ratio) and has about ZERO to do with the problem at hand). This issue as I understand it is in discussing how the two ground wires present in a domestic AC system should be connected to a "quality" audio device.

Click to expand...

Sorry, no. It is 100% to do with having unbalanced (i.e. RCA) connections. In unbalanced connections, one of the two pairs of wire that carry our audio signal is also the electronics ground (i.e. the shield). Any differential between the signal grounds of the source and sink equipment by definition creates a current that flows from one to the other. Multiply that by resistance of the audio interconnect shield and you have your voltage drop. Since audio signals are nothing but voltage levels, this base level voltage drop translates into an audible hum.

Balanced interconnects at both ends means that the audio signal travels over a pair of wires which no longer have a reference to electronics ground. You can now have current flow between the electronics ground and have no impact on noise level since that voltage drop is not going to be seen on the balanced input.

CMRR is an unrelated topic. It would only have relevance if we were talking about noise picked up by the twister pair wires. That is a different topic and has nothing to do with ground loop hum.

I just tie them together at the point of use. Seems to work as all I am doing is doubling the return line.

Click to expand...

Sounds like you are talking about using balanced interconnects with unbalanced devices. That is not what I meant. I meant true balanced connections.

Atmasphere said:

No circuit uses "signal processing circuitry to AC "return" "; this would be considered to be unsafe. This was a practice decades ago when 'AC/DC' radios were still legal.

The proper way to ground audio equipment:

1) chassis ties to AC ground (middle prong on USA AC outlets, green wire)
2) circuit 'floats' at ground potential, being referenced to chassis at all times through some device (likely a resistor) of such value that ground loop currents cannot form.

If this is done, there is no need to place a stake in the garden or the like for additional grounding. The AC ground (which should be at earth potential anyway; if not, contact an electrician) will be quite sufficient.

Any deviation from this plan: you will get more noise, and 'grounding systems' may well seem to improve things, but they will never get things to be as good as they would be if the equipment was properly designed in the first place. It really is that simple.

Click to expand...

I hope people will read Ralph's comments carefully, 'cause it's so true, IMO.

In another thread recently on noise reduction here, I explained that I lifted the ground on my Alpha DAC and amps, and Steve made a comment that I would "hear it" from some folks; but I did not explain why I did that. So the reasons are simple: a) the preamp, to which they all connect, 'floats' the circuit (this is key);and b) the components, on which I lifted the ground, appear to route signal ground to chassis ground (well, I measured that). So in lifting their grounds, I was aiming at creating a larger "circuit" (comprised of the DAC, amps and preamp) that "floats" at ground potential. Et voila, dead silence, and it also renders power cords that shunt noise to ground irrelevant. Obviously, if there is ever a ground fault, I am willing to see my interconnects melt.

It just aches me to be reading about all these "grounding" products in recent threads, which can't add anything if one addresses grounding correctly, as is. Sometimes I wish there were an Audiophile's Handbook To Sensible Engineering... at any rate, Ralph's short and concise post is one of those WBF gems and I hope people take it seriously.

Atmasphere said:

...a problem that the manufacturer of the preamp, amp or whatever should have got right in the first place.

Click to expand...

Agreed. Internal grounding schemas would appear to be inconsistent between a variety of manufacturers.

First I want to thank Atmasphere and Amir for their courteous and explanatory expositions on the subject at hand. Thank you gentlemen!.

In regards further comments. There is NO "stake in the ground" on my (or any other I have ever seen) domestic electrical system (three wire AC - coming from a center-tapped transformer "on the pole" (or underground in this era)). The feed to the distribution transformer is 4k volts. This feeds a 'step down' transformer with a center tap which provides your house with three feeds; the center tap (AC return) and two 120 volt feeds which are 180 degrees out of phase with each other. Please note that this is NOT a multiple phase system as found in commercial settings - in those you have three "hots" at about 220 volts which are referenced in either a "WYE" or a "Delta". But such is not our concern.

The generator and the switching yard at the "plant" does have a "stake in the ground" but this has more to do with the "electrical mass" of the earth (it can sink almost any voltage potential (hence lightening)). That stake at the plant is irrelevant to the distribution system to domestic sites.

In regard "Ack" comments? Sorry they were to my reading more than a little confusing. So lets define some terms to help us all understand each other.

AC Return; the line that leads back to the "pole" (transformer) and its center tap. The true reference for each of the AC legs.

AC "hot"; the line that holds a nominal 110 volt alternating potential referenced to most accurately "AC Return". If you drop this wire on the "dirt" (physical earth) OR get between this wire and the physical earth (especially if said earth is "wet") you can get a nasty shock - or die.

Earth Ground: the mythical(and physical) ability of the geological earth to absorb potential voltage and current flows - why lightening strikes the earth. A rather large ball that we live on.

House Earth Ground; the third wire in modern AC domestic systems - which ties BACK TO THE AC RETURN AT THE DISTRIBUTION BOX. This wire may or may NOT actually attach to the earth. In all examples I have seen (about a dozen) there is NO STAKE IN THE GROUND TO WHICH THIS IS TIED.

The discussion at hand? Which of the TWO AC RETURN LINES should be tied to your equipment? And how and where should they be attached.

I just tie the things together AT THE COMPONENT. This is my thinking - and until I hear a very clear reason not to do so - I am sticking to such.

valkyrie said:

I just tie the things together AT THE COMPONENT. This is my thinking - and until I hear a very clear reason not to do so - I am sticking to such.

Click to expand...

If I am reading this right this is not a good practice.

Further clarification for USA 'wall' wiring in a house: Black is the 'hot' wire, white is the neutral (AC return) and green is the earth ground.

For safety purposes the chassis should be grounded. You can get away with not doing this only if the chassis is non-conductive. To ground the chassis it is tied to the green wire via the middle prong of the AC power cord (middle prong of IEC connector). Imagine touching the chassis while barefoot in the basement with a foot of water on the floor. What if you have a loose connection somewhere in your AC wiring? The very real possibility in this scenario is that you are dead.

The black wire shall encounter a fuse first thing upon entering the chassis. The fuse is then in series with whatever power switching exists as well as the AC load (power transformers and the like). There is of course a return circuit that must exist for the transformers and such- they can be connected directly to the neutral connection (white wire). This allows the fuse to blow in bad situations, for example the AC switch becomes damaged and shorts to the chassis.

Despite the green and white wires appearing to be the same thing they are not. The green wire frequently has ground connections to conduit, water pipes (because water pipes are often at ground potential) and the like; the white wire does not although it shares a connection at the breaker box. It carries the AC current while the green wire is the ground and normally only carries very tiny currents unless something is really wrong. If you join the two together at the chassis you have the AC return currents active in the chassis. In actual manufacturing this is illegal and dangerous- if a failure occurs it could result in the chassis becoming live and representing a serious shock hazard. In the old days, AC/DC radios had the neutral connection (in theory) tied to the chassis. Quite often though the power cord was not properly polarized so such radios were usually housed in a non-conductive cabinet.

In short (of you will pardon the expression) you may be getting away with it but such is not proper electrical practice.

To quote Atmasphere; In short (of you will pardon the expression) you may be getting away with it but such is not proper electrical practice.

Great pun - thanks. With all the heavy seriousness usually accompanying discussions of stereo kit I really appreciated your light hearted reply. Thanks.

BUT - I keep returning to this and seem to make no headway. The "Green Wire", referred to as "Earth Ground" IS TIED TO THE AC RETURN AT THE BOX. One more time; those two wires are the same electrically. Go measure the resistance with an DVM - they are the same wire at the same potential from an electrical standpoint.

The "Earth Ground" (green wire) is there for safety purposes - to address a failure of either the shell of a component becoming "hot" (at AC potential) OR a failure in the AC Return (white) wire. The old technique of providing an "extra ground" via the plumbing is no longer done - for several reasons one being that many houses use PVC - or other plastics - on the discharge side of the plumbing.

The problem with having the chassis on "earth ground" and the signal processing (I AM NOT REFERRING TO DSP) circuitry on AC Return is that you have the possibility of there being a difference in their relative resistance (from the component to the distribution box). In that case you have AC "hum"; a ground loop where currents run through the returns (both).

It seems rather simple to me; two wires, both attached at some distance, therefore both sitting at the same relative potential. What can you do wrong by tying them together at the component - other than removing the possibility of ground loops? This idea of "floating" the signal processing circuitry seems rather off to my thinking. In fact to do the "float" is to introduce the very real possibility that the shell (case) in the case of a failure, becomes the AC Return and thus an inadvertent "touch" could put the user "in the circuit". So to speak.

You may be sure Atmasphere, that if I ever have the good fortune to acquire a set of your fine sounding amplifiers that I will quickly tie the two lines together. Since any such acquisition will be on the secondary market I don't have to worry about voiding any warranties ;-)). I have done this on numerous ST-70 rebuilds - and they seem to sound wonderful (or at least there is no sonic detriment to my doing so).

I guess we have beat this to death. Thanks again to all contributors voicing their opinions and insights. It was a thoughtful and pleasant experience.

On the ST-70 the unit is not grounded unless you are doing a mod or dealing with a newer unit. For that reason on any vintage ST-70 both sides of the line are isolated from chassis.

While it is true that the ground wire is handled differently in new construction, you can't count on that in a universal fashion.

Tying both connections together does not eliminate the possibility of ground loops by any means. If you have not run into trouble its just because you have been lucky.

Just be aware that your wiring practice is considered dangerous and if you sell anything that you have wired that way, be sure to correct it before selling so as not to take on a liability.

Our warranties are transferable- so it being sold used is not an assurance that one of our products is not under warranty, just so you know.

valkyrie, while it's true the neutral and ground are tied together at the service entrance they serve completely different functions and mixing the neutral and ground wires after the service entrance is very dangerous. Also, there is absolutely no good reason to do this. I can tell from what you wrote you misunderstand this point.... just because they are tied together at the service entrance does not make them interchangeable! If you live alone feel free to take your chances but if you live with others please consider the worst possible outcome, their death, may be your fault and if it causes a fire your insurance won't pay.

I also agree with c1, grounding practices vary and are misunderstood. Running power to an AV system from the service entrance is also frequently misunderstood and often done in a way that promotes noise as a result of ground currents. To further the problem even more, most cable designers don't understand the function of the ground wire in their own cables and make poor design choices. The result of poor grounding schemes in components, cables AND the house electrical system opens the door for aftermarket grounding products. If grounding was handled properly I do not believe these devices would be nearly as popular as they are, because their effects would be minimal to none.

It's my opinion that AC power and cables are the backbone of a system, but are also one of the things often done in a way that is nowhere close to optimal. This results in currents flowing in the shields and ground connections of your cables, which couple to the signal and cause noise.