Venue outlets have open ground. What does that mean?

[micguy]

It means the wiring is old (2-wire), and there's no earth ground for the circuit. If there's a circuit breaker, you should be okay.

Circuit breakers protect the wire from overheating and starting the building on fire. They do NOT protect you against electrocution - the amount of current that will kill you will not trip a breaker or blow a fuse.

 

[micguy]

So, would dimmers (lighting) on a circuit cause equipment hum?

They are indeed a common cause of hum - there are a lot of ways to get gear to hum even if you're grounded properly. SCR dimmers are particularly nasty.

 

[Old Garage-Bander]

FYI the noise is the symptom of an open ground, not the cause.

Look for a properly working outlet at the venue and use that until they fix it.

For years a guitar player I played with used to run his own amp ground outside the club to a spike in the ground.
Solved so many noisy strat problems.

What Is An Open Ground? - Waypoint Inspection Property Inspection

It is risky to run with an open ground, not a risk I'd be willing to take.

I get that! I'm a mad freak about ground rods... But it can also create additional ground loop errors in some audio situations. Ideally, all grounds should be bonded together, with low impedance (aka large) conductors. The other issue is the type of soil you put the rod in. Good, rich farmland type soil is much more effective for grounding than dry, sandy rocky soil. Even around a house you want to get those rods out a few feet away from the backfill around the foundation.

My favorite, that I used at work was 4" wide solid copper flat strap. That's way overkill for most situations that don't involve high power broadcast transmitters. But boy, even the electricians got all bugged eyed when they'd see that stuff at one of my installations.

 

[fishdude101101]

I'm also not an electrician, but I have had a guitarist friend thrown back against the wall when he stepped up to a mic where the power wasn't grounded. It was a dive where there was an outlet that wasn't grounded and one that was, and people that knew the place knew not to use the ungrounded one.

I believe - and more knowledgeable people can confirm or correct me here - that bringing a rubber mat to stand on when you play can help as a safety precaution.

I would say its more than an un-grounded outlet here. I'm thinking some wiring was reversed here to energize that mic's outside casing.

 

[Koog]

Very good reason to not play that venue. Both equipment and players' lives could be at risk.

Koog

 

[Lostgallifreyan]

Before I dropped out of technical college and went to join the punk scene in Bristol in the early 1980's I learned a bit about electrical wiring and safety.

This meant that when we squatted derelict buildings for mass gigs with Chaos UK, Disorder, Amebix, and others, it was usually me who got to put in a mains line so we could do a gig. I had ONE main rule: Run a single earthed line directly from the incoming 'consumer unit', and NEVER trust ANY of the rest of the wiring in the building except for existing lighting if it was safe enough. All amps and other gear had to route back via that one line because that way it was like a 'star network', which as studio owners can tell you, reduces noise problems, as well as tracing a safe ground from every bit of kit added to the network. (Allowing lighting from existing wiring is actually wise, if it's safe, if the main high current line ever had its upstream fuse blowing, the last thing you want is to drop everyone in the dark at that same instant.)

Once, I was 17 at that time, the police and fire brigade turned up, they could have shut us down, but I explained to them how I'd wired the gear, and told them that at least two other people were watching it with me, all of us staying sober enough to do that, and they let us continue. No-one died, and there was no fire, except for one some other punks put under an unseemly bit of tank-shaped climbing frame nearby that they took a disliking to on moral grounds...

If you're ever doing this officially, use official methods. It's slow but it always pays to do it for any fixed installation.

 

[fishdude101101]

So, at my last gig I noticed that when I turned on the mains with the PA turned off and nothing going to them, there was a huge hum coming from them. So, as I had a handy electrical outlet tester in my kit I decided to test the outlets where the band plays and plugs into and found that there is an open ground. I do not know a lot about electronics and electricity.

What does that mean and more specifically, what dangers - if any - does that pose for the band? Without changing the wiring at the venue, what can I do to mitigate any issues this condition may cause?

Simply tell the venue they need to have a qualified electrician come check everything out. In all likelihood it's just a ground wire came loose on an outlet somewhere down the circuit. But it certainly could be more serious than that. Other than driving a ground rod into the ground and rigging up a ridiculously complicated grounding system, there's nothing you can do about it. (That suggestion was more for humorous affect than anything. Do not attempt that.)

Word of caution about outlet testers. Sometimes "grounded" isn't "grounded"

Let me give you a practical example. Bought an old house last year. A couple of circuits are old "BX" metal clad cable with only 2 conductors, no dedicated groundwire. 2 prong outlets. I replaced them with 3 prong outles but there is obviously nothing to hook the ground on the receptacle to. But they have metal outlet boxes and metal cladding all they way back to the breaker box so they read as "grounded" with an outlet testers, even the one that is only metal clad for about 10 feat to a metal junction box and then is "rag wire" back to the breaker box. Hope that makes sense. I know two fingers was an electricians so he might be able to explain a bit better.

 

[higain617]

NO! A circuit breaker is designed to protect the wiring in the wall from overheating due to more current than the wiring can take. That's about fire safety, not people safety. You can be well on your way to the morgue before that breaker ever trips.

Yeah, you're right. Sorry for the bad info.

OP, does your amp have a ground lift? Flip that if it's humming.

 

[reverendboom]

ummm. I'm still on the first page but GfCI's do not require a ground to work. What they do is monitor the current between the hot and neutral wires and if there is a drop on the neutral (indicating a fault to ground) it trips. BTW, ground means ground not just the bare copper wire in the house.

How does a GFCI outlet work? | HowStuffWorks

 

[Old Garage-Bander]

If the outlets aren't grounded, but you hook the PA and the amps into the same outlet (on a power strip or something), everything will be at the same voltage, so you're relatively safe in that case, but you may very well blow fuses or breakers.

I see what you are saying, and both you and I may have the requisite knowledge to understand the risks and avoid problems. But then along comes some guy who reads without understanding and says. "I saw somewhere on the internet that you can't get electrocuted if you plug everything into the same plug strip even if it's not grounded".

If they don't have a ground on the chassis of all that equipment, and there is a wiring fault inside one of those pieces of gear, they can still get zapped. You can touch two chassis that both are hot, but only as long as you have no other paths to ground, neutral or some other sneak path to a different voltage potential.
Think about birds sitting on a high tension power line. It's OK because they aren't in contact with another conductor.

 

[reverendboom]

Word of caution about outlet testers. Sometimes "grounded" isn't "grounded"

Let me give you a practical example. Bought an old house last year. A couple of circuits are old "BX" metal clad cable with only 2 conductors, no dedicated groundwire. 2 prong outlets. I replaced them with 3 prong outles but there is obviously nothing to hook the ground on the receptacle to. But they have metal outlet boxes and metal cladding all they way back to the breaker box so they read as "grounded" with an outlet testers, even the one that is only metal clad for about 10 feat to a metal junction box and then is "rag wire" back to the breaker box. Hope that makes sense. I know two fingers was an electricians so he might be able to explain a bit better.

that metal covering was the ground

 

[fishdude101101]

that metal covering was the ground

On at least one of those runs it is not really grounded, not even close to properly. The metal cladding run about 10 feet to a metal junction box. From the junction box to the breaker box it is cloth covered wire with no ground.

 

[Johnny Crab]

So, as I had a handy electrical outlet tester in my kit I decided to test the outlets where the band plays and plugs into and found that there is an open ground. I do not know a lot about electronics and electricity.
1A) What does that mean and more specifically,
1B) what dangers - if any - does that pose for the band?
2) Without changing the wiring at the venue, what can I do to mitigate any issues this condition may cause?

1A) Means the venue electrician(s) and inspector did not do their jobs correctly. Open ground should've been discovered.
1B) Dangers: possible equipment damage, possibility of electrocution and/or death for band member(s)/crew.
2) Either bring your own DISTRO(and electrician) and correctly wire direct to mains or other properly-wired source....OR....cancel the show and leave.

Most other suggestions put a band aid on what can be a fatal mistake.

 

[reverendboom]

On at least one of those runs it is not really grounded, not even close to properly. The metal cladding run about 10 feet to a metal junction box. From the junction box to the breaker box it is cloth covered wire with no ground.

Clothe cover wire will usually have a smaller ground wire with it. Electricians did not bring that wire into the metal box but connected it outside the box. if your test shows a ground...there's a ground.

I spent 6 years as an electrician and still do lots of remodel work, so I do know of what I speak.

 

[TomB]

Around here with lots of pre-1950 buildings, lack of a separate ground wire is common, and not easily remedied without an overhaul. Our inspectors insist that circuits be protected by GFCI in potentially wet locations, notably kitchens and bathrooms.

 

[51PRI]

Report it to the local government Building and Safety department anonymously. The OSHA at the state level (some states have their own OSHA) or federal level can help. If no one responds, contact the building insurance liability company and tell them the wiring is defective. Ask for peoples names. Say if someone is hurt, you will report that you told them on a particular date and their lack of action resulted in a death.

Yeah, that'll get you rebooked there. More likely cause the place to get shut down. If the OP reported it to the owners 10 years ago and it didn't get fixed, even with new owners, that means it was too expensive.

 

[Lostgallifreyan]

OP, does your amp have a ground lift? Flip that if it's humming.

Don't do that! Seriously... Leave it set to make the proper ground connection unless totally sure that it's only acting in the audio ground, and the electrical ground is hardwired and links to a properly grounded outlet too. 'Ground lift' is a Seriously Bad Idea, it should never have been invented.

There's a document by Rane called "Grounding and Shielding Audio Devices" that goes into this at length, but its an easy read, and has influenced the better habits of modern audio gear makers.

 

[Lostgallifreyan]

I know two fingers was an electricians so he might be able to explain a bit better.

There is something about that remark that is a tad unsettling. Now if he still had them all...

 

[MVE]

I'm also not an electrician, but I have had a guitarist friend thrown back against the wall when he stepped up to a mic where the power wasn't grounded. It was a dive where there was an outlet that wasn't grounded and one that was, and people that knew the place knew not to use the ungrounded one.

I believe - and more knowledgeable people can confirm or correct me here - that bringing a rubber mat to stand on when you play can help as a safety precaution.

Rubber Mat?!?!?
No!
People are injured when the current passes across their chest (ie: one hand to the other hand) and stops their heart.
This can happen when one hand is touching something charged, (like the strings of your guitar if your ungrounded tube amp is leaking voltage to the chassis), and then you touch something that is properly grounded with the other hand. (Like a mic stand) Zap!

If your tube amp is plugged into a properly grounded outlet, that voltage would go there instead of through you.

 

[groovepump]

I use an isolation transformer for my rig. Cuts down ground noise, and allows me to avoid getting shocks off of others, and their mics. NOT a replacement for a good PE (protective earth) connection, but eliminates voltage differentials with others.