amplifier humming & recording room ground looping

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bohl1076

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hello, i figured this would be a grounding issue! i was talking to a friend who has a recording studio at his house, but can't seem to get rid of the humming and noise interferance from his equiptment. right now i'm scratching my head cause i haven't dealt with much audio stuff before, but am going to check it out next week. can anyone give a suggestion as to what i can do/or look for, that may help?
thanks, bohl1076
 
Well every time we do a job a Disney or universal studios after final inspection .

The geek sound techs take the grounds off the power outlets this is not code but thats what they do the reason is if a super star is on stage and they get feed back its very expensive so its better to have no ground . Audio is very touchy

Let me clearly state we dont they do it after were done .
 
First and foremost, there should be a single point ground, if there are loops there will be noise.


Roger
 
Well its real funny but when the big boys like CNN or TURNER or CBS come down to florida at Disney or Daytona raceway they dont use the power they bring there own mobile power generators and stuff for there boardcasting mobile sat stuff even if the event is inside they use there own power .

Or at a pro golf event its there own power mobile yes its a single grounding thing that audio will pick up the ac 60 cycle or any trash online and amplify it .
 
bohl1076 said:
hello, i figured this would be a grounding issue! i was talking to a friend who has a recording studio at his house, but can't seem to get rid of the humming and noise interferance from his equiptment. right now i'm scratching my head cause i haven't dealt with much audio stuff before, but am going to check it out next week. can anyone give a suggestion as to what i can do/or look for, that may help?
thanks, bohl1076
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Make sure all equipment is fed from the same leg of the panel if possible, make sure all equipment grounds are intact, make sure your friend is not using cheap "Radio Shack" audio cables, make sure all audio cables are routed as far away from AC power as much as possible, and where AC and audio cross, try to do so at a 90 degree angle to help avoid hum field coupling.

That's about all I can think of to advise online..PM me, if you're local to me in So Cal perhaps I can meet with you to help troubleshoot this.

ohmhead said:
Well every time we do a job a Disney or universal studios after final inspection .

The geek sound techs take the grounds off the power outlets this is not code but thats what they do the reason is if a super star is on stage and they get feed back its very expensive so its better to have no ground . Audio is very touchy

Let me clearly state we dont they do it after were done .
Click to expand...

I don't care who the client is, if had knowledge of this kind of dangerous practice I would be making some phone calls and getting them shut down. :mad:

Those sound techs aren't geeks, what they are is something I cannot say on a family-friendly forum, but I promise if they were working for me they would be fired immediately for this!!

There is ABSOLUTELY NO EXCUSE for removing grounds on ANY sound system!! If it is properly wired with reasonable quality cabling there are rarely if ever hum issues. If it hums, there are issues that need to be addressed.

By the way, feedback and hum are two entirely different things and feedback is caused by improper system equalization, NOT Ground issues. If those techs don't know the difference then they are even bigger things I can't say here.

And I would rather have an annoyed superstar than one being electrocuted in front of an audience, which WILL happen in the case of those morons.
 
it is going to be about having the same leg of power. Probably there is an outlet on either leg of power with both being used for different pieces of equipment. the audio equipment is so low in amperage that he could run most of his gear on one 15a circuit. use a power strip and extension cords to check this. And of course no dimmers/fluorescents without bypass ability.

I don't agree that the ground is NEVER at fault. I would not condone removing it, but it solves a lot of audio issues. As an electrician, I am not convinced the ground is a big lifesaver, but of course I do not lift it. When I am helping troubleshoot audio issues, I will lift it to see if it helps. Then replace it, and inform the person that lifting it helped. But I recommend against it.
 
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mxslick said:
Make sure all equipment is fed from the same leg of the panel if possible, make sure all equipment grounds are intact, make sure your friend is not using cheap "Radio Shack" audio cables, make sure all audio cables are routed as far away from AC power as much as possible, and where AC and audio cross, try to do so at a 90 degree angle to help avoid hum field coupling.

That's about all I can think of to advise online..PM me, if you're local to me in So Cal perhaps I can meet with you to help troubleshoot this.










I don't care who the client is, if had knowledge of this kind of dangerous practice I would be making some phone calls and getting them shut down. :mad:

Those sound techs aren't geeks, what they are is something I cannot say on a family-friendly forum, but I promise if they were working for me they would be fired immediately for this!!

There is ABSOLUTELY NO EXCUSE for removing grounds on ANY sound system!! If it is properly wired with reasonable quality cabling there are rarely if ever hum issues. If it hums, there are issues that need to be addressed.

By the way, feedback and hum are two entirely different things and feedback is caused by improper system equalization, NOT Ground issues. If those techs don't know the difference then they are even bigger things I can't say here.

And I would rather have an annoyed superstar than one being electrocuted in front of an audience, which WILL happen in the case of those morons.
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Well first your concern is noted .

But when we get done with a job i really dont look back its over done finished we did our part its there bussiness practices its there people .

Point is the sound tech geeks at disney or universal have the ability and electronics back ground .

May you should apply for a job there and let them know what there doing wrong because iam not we like there projects its income .

Did you know disney has there own building dept and its own electrical rules & regs .

There a city on there own they do not use your local or county electrical inspectors .

But they use the NEC on us during construction .

What do you do when you have a insulated tool install a ground on it ?

Relax think about it i think there poeple are highly able and know what there doing .

we did not take ground off they did !

I dont think they use radio shack equipment at Disney or universal studios.

Example orange county convention center does it also the sound crew takes it off during a big show like during a concert you need to ask them why .:roll:
 
Well, it just so happens that I have a recording studio in my basement.
It is a 32 Channel multi track with unlimited tracking and playback.

There is (2) 20amp circuits that feed receptacles in the 'main' recording room.
There is (2) 20amp circuits that feed receptacles for board, gear, and computer.
There is (2) 15 amp circuits that feed lighting.

This is all wired in NM with plastic boxes.
The vocal booth has a 3'fluorescent light.
All of the recessed lighting have CFL's.

I have KRK powered Rockit8 nearfield monitors with standard powered Altec's for reference.
The heat in the Main recording room is baseboard electric.
There is no heat in the control room. It stays nice and cool.

There is not a whisper of hum or noise in my system.
Mainly due to the common Ground Point.


If your friend's wiring is complicated, you absolutely can try an isolation transformer. It might help.
I would be interested if he has some strange bonding going on to water lines or something else.
 
ohmhead said:
The geek sound techs take the grounds off the power outlets this is not code but thats what they do the reason is if a super star is on stage and they get feed back its very expensive so its better to have no ground .
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ohmhead,
feedback and ground hum are not the same thing.

If a Super Star is onstage getting feedback, the Monitor Mix Engineer is going to take care of it. Pretty Quick, too.
 
ohmhead said:
Point is the sound tech geeks at disney or universal have the ability and electronics back ground.
Click to expand...
Electronics wizzes want to over-ground most of the time. They usually want to drive their own seperate ground rods.

Relax think about it i think there poeple are highly able and know what there doing .
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Now that's funny.
They Should, but do they?

ohmhead, have you seen this done, or is this jobsite talk?
I have a hard time believing that they would not be using isolation transformers if needed.
Maybe you just didn't see them being used.

I could see their engineers lifting a ground to find the problem, but not leaving it.
 
ty said:
ohmhead,
feedback and ground hum are not the same thing.

If a Super Star is onstage getting feedback, the Monitor Mix Engineer is going to take care of it. Pretty Quick, too.
Click to expand...

Well thank for that info but i kinda know that feedback is not humm from AC power we kinda just wrote that wrong iam not good with the english as noted above .

So now lets talk about grounding loops and unbalance voltages between different chassie grounds on amplifiers to earth ground and what is the solution to the OP s problem thats what were here for not to learn how to spell check each other and define what was writen in a post iam to old to learn that stuff .

As far as i didnt see it we kinda do a complete electrical system we do new contruction for disney were a electrical contractor for them so we kinda did not miss it if they want it its installed per contract on the one line if not they dont get it .
 
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Well lets add this yes i have seen with my eyes the grounds cut off .

Now lets correctly say most of the stage or production is by Disney but set up and sound ect ect is work by subs or event people meaning others not Disney meaning actual disney workers over see it .

Shows or events on stage or concerts or special guest events others come in and use there facility they dont use isolation transformers and they use whats there .

Some areas have isolation transformers but some dont rides and animation control buildings have lots of special power systems but most of the convention centers and hotels dont thats were we see this done by audio techs or people who set up there .

Disney electricians dont fix anything its done by sub contractors they just change bulbs out .

Ive work there for many years in new construction and when we leave are service dept tells us what they changed or did after we left.

But i have also seen the best of Disney there power generation is one of a kind . They dont have a loss of power ever they have there own power plant on site .
 
hum eliminator

hum eliminator

if your signal lines are unbalanced (i.e. 2 conductor like an RCA connector) then you can throw in a hum eliminator made by ebtech. this should eliminate any hums in the system. if they are balanced lines, try lifting the shield on the input. ground loops are one of the hardest things to troubleshoot in a sound system.
 
unbalanced refers to the type of line level audio signal. Your household electronics all use an unbalanced style audio signal (those red and white RCA connectors on the back.) consumer electronics also tend to tie the chasis ground together with the signal ground, or the negative of the signal, which causes a lot of ground hums.
 
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