I did an addition to a church sanctuary a couple of months ago. 12 500W chandeliers with 2 fixtures per 1500W dimmer. All my wiring is in EMT and MC. This is in addition to 16 chandeliers on 8 dimmers that were already there. The sound guys draped their cables through the attic trusses from the back of the sanctuary to the front behind the platform where the amps are. I had installed 2 16"x16"x6" pull boxes where their equipment was to set behind the platform with 2" EMT stubbed up into the attic and down to the crawl so they could go either way they wanted and keep their cables in EMT. They chose to not use them. Now they have a terrible buzzing in the speakers. They told the GC that the electrician needed to reverse the polarity of his wiring and make it positive ground. I installed 6 IG duplex receptacles on dedicated circuits for their equipment. I don't believe their buzzing is my problem. What do you think?
Sound guy needs "positive ground"
- Thread starter amptech
- Start date
- Status
- Location
- Massachusetts
Re: Sound guy needs "positive ground"
Have you done what was required by your contract?
You can not reverse polarity of your circuits no matter what the sound guy says.
I wold leave it as their problem.
One question, you said you ran IG circuits, where are the IGs terminated?
Have you done what was required by your contract?
You can not reverse polarity of your circuits no matter what the sound guy says.
I wold leave it as their problem.
One question, you said you ran IG circuits, where are the IGs terminated?
sheldon_ace
Member
- Location
- Owego, NY
Re: Sound guy needs "positive ground"
contrary to popular belief, the buzzing is not a result of any wiring done by the electrician. I have worked as a sound engineer with professional concert audio companies for the last 10 years. I have also been in the electrical trade for as many years. This has been a large myth formed by "audio guys" not knowing what the hell they are doing. I have heard many times over, that when a buzz developed in the system, it was chaulked up to "dirty power"...
I have to constantly explain to my colleages in the audio industry, that the problem results from ground loops in their signal wiring between their processing equipment and the amplifiers. All the amplifiers do is "boost" the signal it recieves from the equipment up stream.
Typically a buzz results from companies who build the signal processing equipment (mixers, effect units, etc.) like to tie the signal "shield" (that bare wire that wraps around the two conductors in microphone cables) to the equipment chassis ground. If even millivolts of potential are found on the equipment grounding conductor, this will also be found on the shield. The sole purpose of the shield is to protect the 2 wire conductors from ambient electromagnatism and radio waves. Basically anything that tries to induce a voltage on the conductors will be bled off by the shield which should only be tied to earth ground at the amplifiers. (If it is earth grounded at two points, then a buzz results)
So if you want to get those audio guys to shut up and mind to their own work, tell them to check their system, and signaling equipment for ground loops....
contrary to popular belief, the buzzing is not a result of any wiring done by the electrician. I have worked as a sound engineer with professional concert audio companies for the last 10 years. I have also been in the electrical trade for as many years. This has been a large myth formed by "audio guys" not knowing what the hell they are doing. I have heard many times over, that when a buzz developed in the system, it was chaulked up to "dirty power"...
I have to constantly explain to my colleages in the audio industry, that the problem results from ground loops in their signal wiring between their processing equipment and the amplifiers. All the amplifiers do is "boost" the signal it recieves from the equipment up stream.
Typically a buzz results from companies who build the signal processing equipment (mixers, effect units, etc.) like to tie the signal "shield" (that bare wire that wraps around the two conductors in microphone cables) to the equipment chassis ground. If even millivolts of potential are found on the equipment grounding conductor, this will also be found on the shield. The sole purpose of the shield is to protect the 2 wire conductors from ambient electromagnatism and radio waves. Basically anything that tries to induce a voltage on the conductors will be bled off by the shield which should only be tied to earth ground at the amplifiers. (If it is earth grounded at two points, then a buzz results)
So if you want to get those audio guys to shut up and mind to their own work, tell them to check their system, and signaling equipment for ground loops....
physis
Senior Member
Re: Sound guy needs "positive ground"
Is the building powered by a DC system?
Is the electrician responsible for the design of the audio equipment?
Are they talking about they're equipment's chassis grounds?
They haven't actually identified their problem yet so their advice to the GC is baseless.
What does that even mean?
Is the building powered by a DC system?
Is the electrician responsible for the design of the audio equipment?
Are they talking about they're equipment's chassis grounds?
They haven't actually identified their problem yet so their advice to the GC is baseless.
hardworkingstiff
Senior Member
- Location
- Wilmington, NC
Re: Sound guy needs "positive ground"
It just gets under my skin when incompetent people blame the "wiring" (always insinuating the electrician) when they don't know what to do.
In the gas station control business, the service techs almost always at the 1st sign of a problem at the initial start up point to the wiring as the problem. It is the equipment problem 95% of the time (yes I am human and make mistakes).
MAN THIS CHIT GETS ME FUMED!
It just gets under my skin when incompetent people blame the "wiring" (always insinuating the electrician) when they don't know what to do.
In the gas station control business, the service techs almost always at the 1st sign of a problem at the initial start up point to the wiring as the problem. It is the equipment problem 95% of the time (yes I am human and make mistakes).
MAN THIS CHIT GETS ME FUMED!
Re: Sound guy needs "positive ground"
Iwire said,"One question, you said you ran IG circuits, where are the IGs terminated?"
The IG circuits originate from a separate panel than the lighting circuits in a different part of the building. It is all single phase 800A service.
Iwire said,"One question, you said you ran IG circuits, where are the IGs terminated?"
The IG circuits originate from a separate panel than the lighting circuits in a different part of the building. It is all single phase 800A service.
hurk27
Senior Member
- Location
- Portage, Indiana NEC: 2008
Re: Sound guy needs "positive ground"
I too have done sound for many clubs and shows and it can be either electrical or audio and even can be the power cords they used to hooked up the equipment.
Let me explain what I'm trying to say.
If a neutral has grounded in one of the receptacle box's or somewhere on its way back to the panel there will be current on the grounding of this circuit, if someone has mis-wired a cord plug by switching the ground and neutral there will be current on the grounding,
Now when we connect two or more pieces of equipment to two different power sources, then connect audio links between them we now have placed a piece of the audio shielding in this path as a parallel conductor and since current takes all paths to source this current will also be on the shielding.
This will impose a 60 hz signal to the amp input and since it is within the frequency range of amplifying it will do just that amplify it.
If this problem is present and the equipment is fed from two different circuits in different conduits it is most likely there is current on the grounding or there is a sub-panel that has the grounds and neutrals bonded or only 3-wires have been run to it.
To find it shut off breakers that don't feed the sound equipment, then turn on each one to find which circuit is causing the ground loop.
If the hum is still there then the circuit feeding the amps or mixer board is subject.
If the load of the amplifiers are the cause then temporally feed the amps from another circuit if it goes away then checkout the circuit that feeds the amps, if it doesn't then check out the mixer board's circuit or any equipment that connected to the mixer board. (Or have the sound men isolate it down to which equipment causes the hum by disconnecting all inputs to the mixer. If still there it has to be either mixer circuit or amps circuit))
Check this circuit out to look for grounded neutrals or just shut off all the circuits in this conduit and remove the neutral(s) from the neutral bar then check to see if there is voltage first then check for continuity to neutral bar. If you have continuity then you have a grounded neutral.
There should never be any current on the grounding after the main disconnect in a building (I'm not talking about the GEC)
Equipment grounds should not have current on them and this includes the conduit. If it does then you have potential for a shock hazard or a fire.
This has been a problem in the sound industry for years and in almost all cases it is because of a neutral grounded or a load pulling power through the grounding, and the fact that many sound men don't know how to wire a plug on the end of a cord.
The only time I ran into a venue that this wasn't the problem was when we had equipment being fed by two different services that did use the grounded conductor as a grounding at each service as allowed in the NEC 230. There was no work around but to install the isolation transformers to keep the bands from using ground cheaters on their equipment power cords.
We had to correct the problem with 1 to 1 isolation audio transformers in the audio feeds to the amp's or the stage DI breakout box I always keep a supply of Switch Craft 1 to 1's handy and in all for mats IE XLR, ?" phono jack, and RCA. with both male and female to accommodate all hookups.
I hope this gives you some insite to the problem.
Many older churchs will have sub panels that are not wired to the NEC by having only 3 conductors to them or haveing the grounding and neutrals on the same buss-bar. Both a no-no but very common.
I too have done sound for many clubs and shows and it can be either electrical or audio and even can be the power cords they used to hooked up the equipment.
Let me explain what I'm trying to say.
If a neutral has grounded in one of the receptacle box's or somewhere on its way back to the panel there will be current on the grounding of this circuit, if someone has mis-wired a cord plug by switching the ground and neutral there will be current on the grounding,
Now when we connect two or more pieces of equipment to two different power sources, then connect audio links between them we now have placed a piece of the audio shielding in this path as a parallel conductor and since current takes all paths to source this current will also be on the shielding.
This will impose a 60 hz signal to the amp input and since it is within the frequency range of amplifying it will do just that amplify it.
If this problem is present and the equipment is fed from two different circuits in different conduits it is most likely there is current on the grounding or there is a sub-panel that has the grounds and neutrals bonded or only 3-wires have been run to it.
To find it shut off breakers that don't feed the sound equipment, then turn on each one to find which circuit is causing the ground loop.
If the hum is still there then the circuit feeding the amps or mixer board is subject.
If the load of the amplifiers are the cause then temporally feed the amps from another circuit if it goes away then checkout the circuit that feeds the amps, if it doesn't then check out the mixer board's circuit or any equipment that connected to the mixer board. (Or have the sound men isolate it down to which equipment causes the hum by disconnecting all inputs to the mixer. If still there it has to be either mixer circuit or amps circuit))
Check this circuit out to look for grounded neutrals or just shut off all the circuits in this conduit and remove the neutral(s) from the neutral bar then check to see if there is voltage first then check for continuity to neutral bar. If you have continuity then you have a grounded neutral.
There should never be any current on the grounding after the main disconnect in a building (I'm not talking about the GEC)
Equipment grounds should not have current on them and this includes the conduit. If it does then you have potential for a shock hazard or a fire.
This has been a problem in the sound industry for years and in almost all cases it is because of a neutral grounded or a load pulling power through the grounding, and the fact that many sound men don't know how to wire a plug on the end of a cord.
The only time I ran into a venue that this wasn't the problem was when we had equipment being fed by two different services that did use the grounded conductor as a grounding at each service as allowed in the NEC 230. There was no work around but to install the isolation transformers to keep the bands from using ground cheaters on their equipment power cords.
We had to correct the problem with 1 to 1 isolation audio transformers in the audio feeds to the amp's or the stage DI breakout box I always keep a supply of Switch Craft 1 to 1's handy and in all for mats IE XLR, ?" phono jack, and RCA. with both male and female to accommodate all hookups.
I hope this gives you some insite to the problem.
Many older churchs will have sub panels that are not wired to the NEC by having only 3 conductors to them or haveing the grounding and neutrals on the same buss-bar. Both a no-no but very common.
big john
Senior Member
- Location
- Portland, ME
Re: Sound guy needs "positive ground"
[ August 09, 2005, 07:10 PM: Message edited by: big john ]
Find them and tell them that you've already reversed the power polarity 36,000 times in the last five minutes and yet for some reason they still have a hum; it must be on their end.
[ August 09, 2005, 07:10 PM: Message edited by: big john ]
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
Re: Sound guy needs "positive ground"
Actually, to be fair, that would be only 36,000 times (120 x 60 x 5).Originally posted by big john:
Find them and tell them that you've already reversed the power polarity 54,000 times in the last five minutes and yet for some reason they still have a hum; it must be on their end.
-John
Re: Sound guy needs "positive ground"
Sheldon
Big John thats funny
Sheldon
Amptech said he installed 6 IG circuits for the audio equipment. If done correctly the "green" grounding conductor is tied all the way back to the main swith, grounding electrode conductor and the grounding electrode. When the Amps are pluged in the frame should be connected to the "green" grounding conductor and thus the shield is also connected to "ground". If installed correctly there should not be any voltage on the "green" conductor.
stud696981
Senior Member
Re: Sound guy needs "positive ground"
"Positive Ground"....sounds like a car stereo tech. I have only heard of positive ground on some motor vehicles. Also this tech probably doesn't know the difference between AC & DC!!!
"Positive Ground"....sounds like a car stereo tech. I have only heard of positive ground on some motor vehicles. Also this tech probably doesn't know the difference between AC & DC!!!
Re: Sound guy needs "positive ground"
Now, some dimmers generate enough noise to be a problem. I have a pair of Levitons which interfere with my 56K modem, but I no longer use that. They also create noise in my portable telephone. I would think though that a properly designed and installed audio system would not be affected by noisy dimmers.
And, what in the pluperfect is a "positive ground"? They did that on some old Fords, but that was DC!
[ August 08, 2005, 11:47 PM: Message edited by: rattus ]
Now, some dimmers generate enough noise to be a problem. I have a pair of Levitons which interfere with my 56K modem, but I no longer use that. They also create noise in my portable telephone. I would think though that a properly designed and installed audio system would not be affected by noisy dimmers.
And, what in the pluperfect is a "positive ground"? They did that on some old Fords, but that was DC!
[ August 08, 2005, 11:47 PM: Message edited by: rattus ]
physis
Senior Member
Re: Sound guy needs "positive ground"
The cheap cable I got with my DSL has no shielding. If you're having noise problems yours might benefit from a shielded cable.
Between my modem and tele jack I don't think there's a grounding means available but an old goat retired engineer like yourself couldn't possibly be detered by a minor technicality like that.
The cheap cable I got with my DSL has no shielding. If you're having noise problems yours might benefit from a shielded cable.
Between my modem and tele jack I don't think there's a grounding means available but an old goat retired engineer like yourself couldn't possibly be detered by a minor technicality like that.
robcircuits
Member
Re: Sound guy needs "positive ground"
One thing is clear... the audio installer did a poor installation, as well as does not know what the heck they are talking about! How grassroots are these guys??? There are definitely several potential causes for the "buzz". First of all, is it really a buzz (aka a nasty, modulated, fairly broadband, sharp-edged sound) or a hum (60-120 Hz tone)? The problems can encompass: audio equipment power ground, noise riding the power lines, audio equipment signal ground ("loops", etc), poor/ incorrect wiring connections, or induction loops/ EMI. The problems are all too common, although the resolutions are straight forward for an experienced technician or systems engineer.
Why did they choose not to use the conduit???
One thing is clear... the audio installer did a poor installation, as well as does not know what the heck they are talking about! How grassroots are these guys??? There are definitely several potential causes for the "buzz". First of all, is it really a buzz (aka a nasty, modulated, fairly broadband, sharp-edged sound) or a hum (60-120 Hz tone)? The problems can encompass: audio equipment power ground, noise riding the power lines, audio equipment signal ground ("loops", etc), poor/ incorrect wiring connections, or induction loops/ EMI. The problems are all too common, although the resolutions are straight forward for an experienced technician or systems engineer.
Why did they choose not to use the conduit???
mvannevel
Senior Member
- Location
- Hesperia, Michigan
Re: Sound guy needs "positive ground"
My John Deere 60 is positive ground. Wonder if those sound guys'd like to rent it from me to see if it fixes their problem.
My John Deere 60 is positive ground. Wonder if those sound guys'd like to rent it from me to see if it fixes their problem.
rick hart
Senior Member
- Location
- Dallas Texas
Re: Sound guy needs "positive ground"
My thinking is the electronic dimmers are creating RF problems being picked up by the long run high gain signal cables. The conduit you provided would not likely mitagate the problem if that is the case. If a separate neutral was supplied to each dimmer load, wiring can be ruled out. I did not see if this is an building dimming or theatrical dimmer system with a remote dimmer rack or a dimmer in the wall. A wall mounted dimmer will cause this sort of noise, especially if the power for ANY piece of equipment in the sound chain is supplied by the same source as the lighting. Since there are amplifiers away from the mixing equipment I believe that there is a strong possibility that the noise is power related compounded by the less than craftsman like audio installation.
I'd be willing to bet that the audio guy bought a ready made snake and all the XLR ends would not fit in the conduit you provided.
What to do:
1. Replace the dimmers with a snap switch to see if they are the bad guys- if so you will need to isolate these from the one supply
2. Verify that all power for the sound equipment is coming from the same source and not from a panel here and a panel there.
3. Verify that neutrals are not being shared with any other circuit that supplies the lights or sound chain.
3. If 1,2 and 3 do not apply- try to arrange the circuits where all circuits for the sound chain are supplied by the same phase- neutral/ground residual voltage may be where the noise is coming from but, I really don't think this will help.
4 Have the sound guy lift signal grounds at the destination end of his stuff- he has a ground loop problem (they almost always do).
My thinking is the electronic dimmers are creating RF problems being picked up by the long run high gain signal cables. The conduit you provided would not likely mitagate the problem if that is the case. If a separate neutral was supplied to each dimmer load, wiring can be ruled out. I did not see if this is an building dimming or theatrical dimmer system with a remote dimmer rack or a dimmer in the wall. A wall mounted dimmer will cause this sort of noise, especially if the power for ANY piece of equipment in the sound chain is supplied by the same source as the lighting. Since there are amplifiers away from the mixing equipment I believe that there is a strong possibility that the noise is power related compounded by the less than craftsman like audio installation.
I'd be willing to bet that the audio guy bought a ready made snake and all the XLR ends would not fit in the conduit you provided.
What to do:
1. Replace the dimmers with a snap switch to see if they are the bad guys- if so you will need to isolate these from the one supply
2. Verify that all power for the sound equipment is coming from the same source and not from a panel here and a panel there.
3. Verify that neutrals are not being shared with any other circuit that supplies the lights or sound chain.
3. If 1,2 and 3 do not apply- try to arrange the circuits where all circuits for the sound chain are supplied by the same phase- neutral/ground residual voltage may be where the noise is coming from but, I really don't think this will help.
4 Have the sound guy lift signal grounds at the destination end of his stuff- he has a ground loop problem (they almost always do).
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