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

jaswrx

DJ Extraordinaire
Feb 15, 2015
198
33
no, nothing. I will triple check everything next gig, but as I mentioned, once plugged into a source it pretty much goes away. Certainly odd.

Also, it does it on both speakers. It's not a one speaker does it situation...

I have checked at home, and it does not do it, so either it was the venue's lack of "earth ground" or something else in my chain. Of course, nothing has changed, and i didn't even have anything else plugged in for that test. I even swapped power and xlr cables just to see.

Also, humX is only rated for 7 amps which is really pushing it having the whole system (pair of ES1203) plugged into it.
 
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tunes4046

DJ Extraordinaire
Jul 24, 2008
5,881
48
Fennimore Wi
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:
I always have the generator in the trailer ready to go, more than once it has saved a party during a power outage and resulted in very significant tips
 
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andywilson

Active DJ
May 19, 2010
41
Auckland, New Zealand
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.
Certainly could come in handy when you really need power and dont want the hassle and cost of buying a generator.

I've got a couple of battery back up speakers for my DJ emergency's where power goes out but an inverter device used from the car could be good as a home emergency.
 
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ittigger

Hundred Acre Industry Icon
Feb 1, 2011
12,911
Western Maryland
While you can certainly use your car's engine as a generator, it is not a powerplant - and you will not get alot of power from it.

Example, if you use a 440w inverter to convert 12vdc into 110vac, you will be limited to 4 amps. You won't be running much on 4 amps. A typical vehicle alternator will put out about 200amps at 14.5 vdc. This does not mean you have 200amps at 110vac.
 
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DJ Bobcat

DJ Extraordinerror
Nov 8, 2014
10,899
Oklahoma City
While you can certainly use your car's engine as a generator, it is not a powerplant - and you will not get alot of power from it.

Example, if you use a 440w inverter to convert 12vdc into 120vac, you will be limited to 4 amps. You won't be running much on 4 amps.
^^^^ Totally agree with this. My minivan has a built-in inverter and a couple of standard household outlets, but only meant for a light or two, or maybe a small cooler; NOT a PA system.


Sent from my iPhone using Tapatalk
 

steve149

Veni, Vidi, Lusi
Staff member
Sep 26, 2011
32,436
Prospect, CT
I think there have been some conversions of Hybrid EVs to have the small gas engine drive a higher capacity inverter.
 

sawdust123

DJ Extraordinaire
Nov 10, 2006
196
56
Ventura County, CA
If you don't have a good ground but have a 3-prong device, the ONLY safe solution is to use a GFCI adapter. There are some that plug right into the outlet and others that are in-line with a short cord. Expect to pay $15-25 for one.

My advice is to avoid HumX like the plague. It is NOT UL-listed because it is not safe. You are not allowed to put circuitry (semiconductors) on a safety ground. HumX puts parallel back to back diodes on the ground leg. This eliminates ground loops IF AND ONLY IF, the ground loop voltage is less than 0.6 volts (which it often is). However, if you have a true short-circuit situation, the instantaneous current through the ground leg of the HumX will be sufficient to blow those diodes before the breaker pops. When those diodes blow, your device has ZERO safety protection and you can get electrocuted. BTW, HumX only works if there is voltage difference between the grounds of two outlets. If an outlet is missing a ground, it can't serve any purpose.
 

jaswrx

DJ Extraordinaire
Feb 15, 2015
198
33
ok, so a GFCI adapter would be absolutely necessary if I don't have an outlet with earth ground OR even if I do, it seems this is good to have in the chain as even a proper earth ground will not protect fully against shock if there was a fault?

do you think by not having a earth ground, this is what could have caused a slight hum?

and to better educate me, what would a simple multi-outlet surrge protector strip even be doing if on the same chain as a GFCI adapter?

The GFCI adpater should proect me against any voltage spikes thus not needing surge protector?
 
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sawdust123

DJ Extraordinaire
Nov 10, 2006
196
56
Ventura County, CA
GFCIs do not contain surge suppression devices (MOVs). If you are worried about spikes, keep a separate surge suppressor.

A GFCI operates by comparing the current on both prongs of an outlet and if there is even a slight difference in currents, it opens up the circuit. In a properly working circuit the current on both prongs of a plug should be identical. If it isn't, it means that the electrical current has found alternate return path (ground fault) and hence could be shocking someone.

If I hear humming, I first look up the lyrics. Then I look for the following:
* Make sure the gain is down on all unterminated inputs
* If parts of the sound system are plugged into different outlets (e.g. mixers and powered speakers) I will either isolate these parts with a transformer or run an extension cord so both parts are fed from the same outlet.
* Look for motors, dimmers, neon lights and other noise makers close by or on the same circuit. I turn off or move away from the offending source.
* Make sure I am not near any high-current feeds (breaker panel) and move away if I am.
* Check for bad cables
 

jaswrx

DJ Extraordinaire
Feb 15, 2015
198
33
right, but I don't need earth ground to use a GFCI?

besides water, I am trying to imagine what would casue a "ground fault?"
 

DJKLEEN

DJ Extraordinaire
Mar 31, 2016
687
52
Lafayette la
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:
I believe that a good power source is the venue or the customers responsibility. Unless it is an outdoor secluded spot and that should be discussed beforehand. I always tell the customer that I need a good 15 amp outlet.

Yes we own the hum problem.
 
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DJKLEEN

DJ Extraordinaire
Mar 31, 2016
687
52
Lafayette la
A lot of times hum comes from from your powered speakers ground. It may be at a different potential which will cause current flow, which will cause hum through your patch connection.

Here always carry a couple of these.

AB5A0D24-2BB6-4B00-9B1C-56E788FFA1A5.png
 

ittigger

Hundred Acre Industry Icon
Feb 1, 2011
12,911
Western Maryland
right, but I don't need earth ground to use a GFCI?

besides water, I am trying to imagine what would casue a "ground fault?"
'A GFCI monitors the amount of current flowing from hot to neutral. If there is any imbalance, it trips the circuit. The GFCI senses a mismatch as small as 4 or 5 milliamps, and it can react as quickly as one-thirtieth of a second.'

'In a normal 3 pin outlet, the two blades carry the current, and the pin is the ground. The ground pin only carries current when there is a fault in the system. A fault is when something disrupts the usual flow of electricity through the circuit -- if one of the wires gets damaged, or something metal touches an exposed wire. In situations like that, the ground pin will carry the extra current away from the fault and to the ground (literally) which should prevent all the current from going into the fork that you're holding.'

Note: While this does help prevent accidents, it does not stop you from accidentally or intentionally killing yourself by electrocution.

FYI, another electrical safety measure is when you see outlets installed upside down. In a right side up outlet, if you have a vacuum plugged in and something was to cross the blades, that something becomes energized and the outlet would short out. With upside down outlets, the same exact scenario could not happen - but if it did cross 2 blades, one of those blades would be the ground lug.
 
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jaswrx

DJ Extraordinaire
Feb 15, 2015
198
33
To make it very clear, I do not ever have ground loop hum. All my gear is run on one outlet which greatly helps.

Also, DJ KLEEN-don't those adapters just remove the ground, so not exactly the best way to "fix' ground loop since you are now prone to shock if there is a short circuit. An inline audio transformer is the right way to do remove the hum (I use one on my laptop).
 
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sawdust123

DJ Extraordinaire
Nov 10, 2006
196
56
Ventura County, CA
DJKLEEN, the 3-2 prong adapter (aka cheater plug) is not sanctioned for use without a ground connection. That little green tab you see is supposed to be screwed to the outlet which should be grounded to the box. Using it without a ground connection is a liability that you don't want to be caught with. Besides, if lifting the ground kills the hum then you know you can SAFELY kill the hum with a transformer-isolator.
 
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IceBurghDJ

DJ Extraordinaire
Apr 17, 2015
1,680
57
Western Pennsylvania
iceburghdj.com
Everything I have runs on one outlet..maybe for the next school dance it won't since I have more lighting and extra speakers. But all other gigs, yep. I've tested the draw and it's under 15amp. All led lights these days, class d amps, etc.

If I have a hum issue I just do a ground lift (aka 3 to 2 prong adapter). the room in one venue I go to often always has an issue with hum.

how much stuff are you running on a single outlet? just curious..... you running lights and sound together?

cc
 
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djcrazychris

DJ Extraordinaire
Jun 12, 2018
2,290
45
i always try to put sound and light on different circuits... i guess its just an old habit from when i controlled lights with rocker switches and the sound would pop when i clicked each one (if on the same circuit)

cc
 

Proformance

DJ Extraordinaire
Nov 6, 2006
3,282
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.
Ref: Posted video

You're touching a live input pre-amp with your finger on a system with no AC ground. The source of the hum is YOU.
Once you terminated the input with a balanced device connection the hum went away right?

That's not a ground loop it's a drain. You start with an open pre (very low S/N ratio) and then start touching things. You are a ground path and all your gear is interconnected not only by it's cables but also by the rack rails and power cords.

DJ gear in general often has very low quality pre-amps (which is what makes it affordable) and is prone to noise.

Did you also have a PC or it's power supply connected to the system at that time? PC and power supplies will often induce small amounts of low level hum in an audio system unless fully transformer isolated.
 
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