# GROUNDING OF PRO AUDIO: I saw your video on Understanding Grounding in Audio, very good, and I understand the principle of the electricity going back

#### Harold Barber

##### Member
GROUNDING OF PRO AUDIO: I saw your video on Understanding Grounding in Audio, very good one and I read Bill Whitlock´s article. I understand the principle of the electricity going back to the transformer to complete the circuit and "Not to earth"... BUT that is under ideal circumstances, as a live sound engineer I´ve had many situations with electric sources without a grounding terminal (I live in Venezuela) (By the way we have the same grounding system as the US) and I´ve had audio ground problems, sometimes a little hum, sometimes electricity on your lips when you touch the microphone and I´ve solved it by "creating a ground" connecting a wire from the chassis of the mixer to a water pipe, a metal fence or even just sticking a screwdriver yo the ground. I know that probably it won´t provide a safety path in case of a electric short circuit but it does get rid of the AUDIO grounding problems. It seems that SOME noise CAN be drained to earth.

Also in your video there is your explanation of a circuit using a battery an a light bulb is clear BUT what happens if instead of the positive of a battery you use the hot terminal of a 120v AC receptacle and instead of the little bulb you use those voltage detector screwdriver, not the plastic voltage sniffer but the old type with metal tip and you touch the metal plate on the handle and the neon bulb turns on. How is the circuit completed? I even tried it (just for kicks) with my Nike shoes on a plastic chair on a wooden floor and the bulb lights.

My only explanation is that our body mass is capable of absorbing some electrons, enough to light the little current needed by the neon bulb.

The same way the Earth is capable of absorbing the little parasitic current that causes the hum and lip voltage in the first example.

If we accept that Earth is at 0 volts and we have some voltage on the green wire it seems logic that when connecting them together the voltage will drain to earth.

#### Speedskater

##### Major Contributor
Yes, water pipes are where the misunderstandings about connecting to Planet Earth started. All metal water pipes are a good low resistance path back to the building's Neutral. In the old days, a city's all metal water pipe system also formed multiple paths back to the Neutral of that big power transformer down the street.
Steam heating pipes also work great. We used them in a recording of the Cleveland Orchestra in a very old auditorium. (second take, the first one had hum)

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#### Harold Barber

##### Member
Yes, that works, but you assume it as an alternative ways of "Returning to the transformer", which in that case could be correct. My doubt is that there seem to be cases were electricity does NOT seem to go back to transformer but "draining" to earth, despite Amir and Bill Whitlock´s explanation. One is the voltage detector I mentioned but I will give you a real live sound experience that happened to me.

I installed a small sound system in a huge park, no electricity around. They brought a truck loaded generator and sent a long two wire (Live and neutral) to the stage. The truck was on its rubber wheels and had no ground bar (Floating). I had hum in the system, so I took a wire from the chassis of the mixer and stuck it in the ground with a screwdriver and the hum disappeared. It seems noise CAN drain to earth.

#### fpitas

##### Major Contributor
Forum Donor
Because of the power grid, there is a ubiquitous background electric field (and some magnetic field, too) at the mains frequency. I'm guessing you were picking that up.

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#### Harold Barber

##### Member
Probably, but I´m almost sure is the "normal" parasitic current many sound systems produce and that under proper grounded electric systems it drains through the ground cable. The problems arise when there is no ground connection.

#### fpitas

##### Major Contributor
Forum Donor
Probably, but I´m almost sure is the "normal" parasitic current many sound systems produce and that under proper grounded electric systems it drains through the ground cable. The problems arise when there is no ground connection.
Yes, exactly. The field is with respect to the Earth itself, so you need to return the currents there.

#### Speedskater

##### Major Contributor
I installed a small sound system in a huge park, no electricity around. They brought a truck loaded generator and sent a long two wire (Live and neutral) to the stage. The truck was on its rubber wheels and had no ground bar (Floating). I had hum in the system, so I took a wire from the chassis of the mixer and stuck it in the ground with a screwdriver and the hum disappeared. It seems noise CAN drain to earth.
I'm sure that there were some overlooked 'uncontrolled variables'.
There was an Audio Engineering Society paper testing mic cables.
They set-up in a park near an AM broadcast transmitter, using an AC power generator.
When they added a ground rod, the noise increased.

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#### Harold Barber

##### Member
Ground is one of the greatest mysteries in live sound. I´m writing a manual for live sound and I´m searching for "The Truth" on electricity and grounding, difficult to find. I think the greatest problem in that there are two grounding schemes (Actually four, but the II and IT don't count here). There is the TT used in Europe and other countries and the TN used in the USA and other counties, including Venezuela were I live. The TT uses TWO ground rods. This scheme takes all the green ground wires and takes them to an independent second rod, probably the confusion comes from there.

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#### Harold Barber

##### Member
One of my greatest doubts, and the reason I entered this chat, is Amir affirmation on his video that NOISE DOESN´T DRAIN TO EARTH (Based on Bill Whitlock´s papers) But my practical experience, and some of yours, is that it does,

#### DVDdoug

##### Major Contributor
You don't always need an earth ground or power ground neutral to prevent hum. You just need a "common" or "floating ground" for shielding (cables & cabinets, etc.) In fact, floating the audio ground sometimes reduces hum. Maybe most of the time it improves things when you a hum problem but you are removing a safety feature.

The earth/power line ground is for safety. If the microphone (etc.) is earth-grounded you can't get any voltage relative to ground and you won't get current through your body-to-ground. If nothing goes wrong it's not needed for safety but as you said, sometimes you do get voltage on a mic (or from a guitar amp).

In the old days, some tube amps and radios & TVs could get voltage on the chassis. There was a 2-wire plug (no separate ground) and the chassis was (supposed to be) connected to power-line neutral, which is safe of if everything is wired correctly (including the house wiring) as long as nothing goes wrong. The power plugs were polarized but it wasn't foolproof. One blade on the power plug was larger than the other (you still see that) but sometimes it was wired wrong (or re-wired wrong when the plug was replaced) and there are extension cords with un-polarized plugs.

Here in the U.S., we normally have separate wires for the neutral and ground (3 wires to an electrical outlet). The ground wire and neutral are connected together and earth-grounded at the electrical box. So if the power is shorted to the ground connection you get high-current flow through the complete circuit to neutral and the circuit breaker blows. So for example, if something shorts-out inside your amplifier it's impossible to get voltage (relative to ground) on your amplifier case.

Since the neutral and ground wires are essentially in-parallel, and since the ground is only supposed to be used for safety, not for carrying everyday current, newer buildings have a ground-fault sensor/breaker to shut-off power when a small current is sensed through the ground wire or through true earth ground. It used to be only in the bathroom and kitchen where you are likely to touch a pipe and get a "good connection" between your body and earth ground. Now, they might be required throughout the whole building, but I don't know. As you probably know, the current required to get a shock or to kill you isn't enough to blow a breaker. But it will trip the ground fault protection.

I had hum in the system, so I took a wire from the chassis of the mixer and stuck it in the ground with a screwdriver and the hum disappeared. It seems noise CAN drain to earth.
That can also work as a safety ground but it should be something like a pipe driven into the ground. And there should probably be one on the stage as well as at the recording truck and/or the PA mixer. But without a direct wire connection to neutral you won't get enough current to blow a breaker. I'm sure it doesn't meet the electrical wiring codes but it's better than nothing.

#### Speedskater

##### Major Contributor
A stake in the ground will never fill the primary task of the Safety Ground/Protective Earth!
* * * * * * * * * * *
From a day-to-day AC power quality perspective, it matters little whether the AC system connection to Planet Earth is "TN-C-S" (PME), "TN-S", "TN-C", "TT", or "IT".

#### Lambda

##### Major Contributor
Ground is one of the greatest mysteries in live sound.
I don't think its mysterious.

You should never have a signal directly referenced to safety ground (or to earth)
Ideally your signal ground and safety ground have wound have the exact same Potential everywhere.
But in the real world wires have inductance, resistance and capacitance as well as inductive coupling to each other.

Next best thing to make sure there is no currents from the safety ground on the signal ground and vice versa.
But generally you also don't wont you signal ground completely floating in reference to safety ground and earth ground
This is why they should cornet at one point (and only one point to avoid infamous ground loops).

#### Blumlein 88

##### Grand Contributor
Forum Donor
Since the neutral and ground wires are essentially in-parallel, and since the ground is only supposed to be used for safety, not for carrying everyday current, newer buildings have a ground-fault sensor/breaker to shut-off power when a small current is sensed through the ground wire or through true earth ground. It used to be only in the bathroom and kitchen where you are likely to touch a pipe and get a "good connection" between your body and earth ground. Now, they might be required throughout the whole building, but I don't know. As you probably know, the current required to get a shock or to kill you isn't enough to blow a breaker. But it will trip the ground fault protection.
I know this is nit picking. I'd amend your description of GFIC, and how it works. It senses a difference in current between line and neutral. That could be from some current on the safety ground or from some current passing thru you going somewhere else than the wiring. Like if you touch an appliance while holding onto a water pipe. Any tiny difference in current in versus current out trips the GFIC. That is why they also work to protect you even when used on a two wire electrical system.

#### restorer-john

##### Grand Contributor
Forum Donor
I know this is nit picking. I'd amend your description of GFIC, and how it works. It senses a difference in current between line and neutral. That could be from some current on the safety ground or from some current passing thru you going somewhere else than the wiring. Like if you touch an appliance while holding onto a water pipe. Any tiny difference in current in versus current out trips the GFIC. That is why they also work to protect you even when used on a two wire electrical system.

You're not nit picking at all. It's important people know what a RDC/GFCI/ELCB does.

Personally, I think the core balance relay is conceptually more intuitive to explain.

#### Blumlein 88

##### Grand Contributor
Forum Donor
Okay, so how a GFCI works though still a little simplified. Neutral and line both pass thru the middle of a toroidal coil without physical connection to it. As long as current in equals current out they cancel the electric field and the toroidal coil has no voltage on it. If current out becomes less than current in because some of the current is going to ground by another route (like thru a human body), then the toroidal coil has voltage on it from the imbalance which will fire a relay to interrupt the connection. It will do so in milliseconds before damage can be done to a human. It will function at very small current imbalances.

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#### solderdude

##### Grand Contributor
Ground is one of the greatest mysteries in live sound. I´m writing a manual for live sound and I´m searching for "The Truth" on electricity and grounding, difficult to find. I think the greatest problem in that there are two grounding schemes (Actually four, but the II and IT don't count here). There is the TT used in Europe and other countries and the TN used in the USA and other counties, including Venezuela were I live. The TT uses TWO ground rods. This scheme takes all the green ground wires and takes them to an independent second rod, probably the confusion comes from there.

The reason it is mysterious is because 'ground' is not a clearly visible 'path' for most uninitiated. This makes it seemingly complex and voodoo alike but it is simple Ohm's law in the end.

Safety ground is for ... well... safety. So that even when there is something going wrong inside a mains connected device you cannot get a jolt (or worse) when touching mains connected devices.
Audio 'ground' is not really ground. More correct would be calling it 'common' or 'reference'.
These 2 should not have to 'bite' each other but in practice, when multiple devices are connected to each other weird currents (from safety ground and even 'earth') could make it into the audio path.
The more complex it gets (think PA systems and AVR's with all kinds of sources connected to it) the more important a proper safety ground is and one should be working with balanced connections as these are better at separating the 2 different (but often connected) grounds.

Ground rods are to ensure the ground that we walk on (lets call it earth) has the same potential as the safety ground pin on an outlet nearby and should have the same voltage level as 'neutral' there as well.

2 ground rods meters apart may well NOT have the same voltage and when connected with a wire might carry current. A ground rod is only insuring (when verified to have a low resistance) that at that point or somewhat nearby there is no voltage difference between the ground pin (an Neutral) of a mains socket and physical ground (earth) you stand on.

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#### audiofooled

##### Active Member
Since the neutral and ground wires are essentially in-parallel, and since the ground is only supposed to be used for safety, not for carrying everyday current, newer buildings have a ground-fault sensor/breaker to shut-off power when a small current is sensed through the ground wire or through true earth ground. It used to be only in the bathroom and kitchen where you are likely to touch a pipe and get a "good connection" between your body and earth ground. Now, they might be required throughout the whole building, but I don't know. As you probably know, the current required to get a shock or to kill you isn't enough to blow a breaker. But it will trip the ground fault protection.

Nov that you mentioned it, years ago I had a situation of audible hum at the mains frequency. Don't ask how I eventually found out, but the culprit was an old fridge with a bad compressor run capacitor. The cap was an old type with metal casing which was bolted to the chassis. The bugger was sending small current to the ground everywhere in the house, water pipes as well. I replaced the entire fridge and, besides the safety hazard removed, it was one of the best audiophile tweaks ever because all the hum was gone. I don't know if this can apply to the modern household appliances (modern fridges compressors do have run caps too) but maybe it's worth considering.

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#### Cbdb2

##### Addicted to Fun and Learning
Also in your video there is your explanation of a circuit using a battery an a light bulb is clear BUT what happens if instead of the positive of a battery you use the hot terminal of a 120v AC receptacle and instead of the little bulb you use those voltage detector screwdriver, not the plastic voltage sniffer but the old type with metal tip and you touch the metal plate on the handle and the neon bulb turns on. How is the circuit completed? I even tried it (just for kicks) with my Nike shoes on a plastic chair on a wooden floor and the bulb lights.

My only explanation is that our body mass is capable of absorbing some electrons, enough to light the little current needed by the neon bulb.

The same way the Earth is capable of absorbing the little parasitic current that causes the hum and lip voltage in the first example.

If we accept that Earth is at 0 volts and we have some voltage on the green wire it seems logic that when connecting them together the voltage will drain to earth.
The detector works on capacitive currents. I'm sure many here have touched 120v hot with one hand and felt that current but not much else happened. If you grabbed a ground with the other hand you'ld feel a lot more. First case your one plate of a small capacitor, the earth is the other. Second case your just a resistor.

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