What happens if you get to a venue and don't have ground continuity?

jaswrx

DJ Extraordinaire
Feb 15, 2015
198
33
^^Happned last night...

Even though the outlet was 3 prong, it was not grounded, otherwise my power cable would have lighten up.

Is there any danger and what is the risk?

Even with the little hum I had, there would be nothing to fix that?
 

steve149

Veni, Vidi, Lusi
Staff member
Sep 26, 2011
32,436
Prospect, CT
If I was using power tools and working in a slightly wet area, I wouldn't have used an outlet with NO ground. Most audio gear today is self-grounded (except maybe for large amps or older lights) and the threat is minimized from a ground short.

I generally bring one of those little outlet testers in my kit bag and might have gone around looking for one with a ground connection and then just ran some longer extensions.
 

steve149

Veni, Vidi, Lusi
Staff member
Sep 26, 2011
32,436
Prospect, CT
what exactly would happen from a ground short?
If there is a short in your power conductors (frayed power cord, something breaks internally) power will flow through the path of least resistance .. that would normally be the ground (which is typically at a 0 potential level). If the short goes to the device chassis and the chassis isn't connected to ground, then anything that touches the chassis would provide an alternate ground path and you get a "shock" if you or a guest touches it.

With power tools, since you are actually moving the power conductors around, you have a greater chance of causing an issue. With most current audio gear, it's really more of a safety net (not that I wouldn't want a net from a liability issue).
 

steve149

Veni, Vidi, Lusi
Staff member
Sep 26, 2011
32,436
Prospect, CT
ok, thanks for the ground lesson :)

Is there anything to do to remove the hum I was getting?
Sounds like there actually WAS a ground, just maybe not to earth. If everything was in the same outlet, you shouldn't get a ground loop, so maybe it was noise from something else sharing the same ground leg.

The Hum-Xs and such might help, as might lifting the ground shield on 1 or 2 cables.
 

DJ Ricky B

DJ Extraordinaire
Mar 9, 2015
3,826
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DJs should always bring their own Back Up power Source to every gig. Having to use the venue's power to do your job is so 1990s. Hum issues are always the DJ's fault, not the venue's or client's. Generator should be loaded in your car, and ready to go in case power is poor quality at the venue, or in case there is a power outage! It is your fault if the power goes out, and you can't facilitate your job because of it...

o_O:banana::kermit::highlyamused:
 

Jeff Romard

Administrator
Staff member
Sep 4, 2006
12,164
48
Sydney, Nova Scotia
DJs should always bring their own Back Up power Source to every gig. Having to use the venue's power to do your job is so 1990s. Hum issues are always the DJ's fault, not the venue's or client's. Generator should be loaded in your car, and ready to go in case power is poor quality at the venue, or in case there is a power outage! It is your fault if the power goes out, and you can't facilitate your job because of it...

o_O:banana::kermit::highlyamused:
Actually you drive a generator to every gig you just need a way to convert it

Car Generator - Pitches - Dragons' Den - (https://www.cbc.ca/dragonsden/pitches/car-generator)
 

DJ Ricky B

DJ Extraordinaire
Mar 9, 2015
3,826
36
Actually you drive a generator to every gig you just need a way to convert it

Car Generator - Pitches - Dragons' Den - (https://www.cbc.ca/dragonsden/pitches/car-generator)
Wise!

...One of my DJs tell me that leaving your car running at idle actually burns less fuel than a power generator does. He has a heavy duty car battery inverter, and used it a few times when the power in his home went out. He said he left his car running for hours on end, and his car doesn't even burn half as much fuel as a regular generator would.
 
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Jeff Romard

Administrator
Staff member
Sep 4, 2006
12,164
48
Sydney, Nova Scotia
Wise!

...One of my DJs tell me that leaving your car running at idle actually burns less fuel than a power generator does. He has a heavy duty car battery inverter, and used it a few times when the power in his home went out. He said he left his car running for hours on end, and his car doesn't even burn half as much fuel as a regular generator would.
If his car is a go-cart maybe LOL. I would find that really hard to believe on average a 4cyl car will burn close to a gallon an hour a generator maybe 3/4 of a gallon. 8cyl would be closer to a gallon and a half
 

jaswrx

DJ Extraordinaire
Feb 15, 2015
198
33
Sounds like there actually WAS a ground, just maybe not to earth. If everything was in the same outlet, you shouldn't get a ground loop, so maybe it was noise from something else sharing the same ground leg.

The Hum-Xs and such might help, as might lifting the ground shield on 1 or 2 cables.
If it was not to earth, what else would it be grounded to? And would this be a cause for hum?

Sorry, I don't know about this stuff. I really need to educate myself. I appreciate your help.
 
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steve149

Veni, Vidi, Lusi
Staff member
Sep 26, 2011
32,436
Prospect, CT
If it was not to earth, what else would it be grounded to? And would this be a cause for hum?

Sorry, I don't know about this stuff. I really need to educate myself. I appreciate your help.
If there are multiple outlets on the same breaker, the grounds are connected, but if the one that connects directly to the breaker has a fault with the ground line, the others share a ground, but it isn't connected to the panel ground. If you connected gear to multiple outlets, you could have a ground issue between the outlets where the grounds aren't at the same potential level (ie. there's a different voltage relative to ground on each) .. that could cause a ground loop issue and hum. If they're on the same outlet, the hum could be coming through the outlet from another device on the same circuit (in the kitchen for example).
 

jaswrx

DJ Extraordinaire
Feb 15, 2015
198
33
I always put equipment on the same circuit on a single outlet.

So are you saying it's still possible to be "grounded" through a shared common ground even though it is not conected to the earth?
 
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djcrazychris

DJ Extraordinaire
Jun 12, 2018
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how much stuff are you running on a single outlet? just curious..... you running lights and sound together?

cc
 
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DJ Ricky B

DJ Extraordinaire
Mar 9, 2015
3,826
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If his car is a go-cart maybe LOL. I would find that really hard to believe on average a 4cyl car will burn close to a gallon an hour a generator maybe 3/4 of a gallon. 8cyl would be closer to a gallon and a half
He has a 1992 Geo Tracker. 4 CYL.

...He sometimes says a lot of exagerated stuff, so I was raising my eye brow at his claim when he told me.
 
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jaswrx

DJ Extraordinaire
Feb 15, 2015
198
33
Quick video at the venue when packing up. Oddly, it only seemed to make the noise on channel 1, and the other channels were not muted.


Once the input was connected, the hum was not audible to most, especially in a noisy room, but I NOTICED it, and it wasn't right.
View: https://youtu.be/GWk1ROFnQqQ
 
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steve149

Veni, Vidi, Lusi
Staff member
Sep 26, 2011
32,436
Prospect, CT
Quick video at the venue when packing up. Oddly, it only seemed to make the noise on channel 1, and the other channels were not muted.


Once the input was connected, the hum was not audible to most, especially in a noisy room, but I NOTICED it, and it wasn't right.
View: https://youtu.be/GWk1ROFnQqQ
If it's only happening on 1 channel, it's generally NOT the power ground .. especially if nothing was attached at the time. DO you have something like phantom power or some other DSP filter running on that channel?