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Author Topic: Distance between electrical and audio cables  (Read 18987 times)

Nate Armstrong

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Re: Distance between electrical and audio cables
« Reply #20 on: January 16, 2015, 09:49:43 am »

Mike, I know your the power guy.  What do you recommend for this issue / what do you use ?

it seems the video link i posted is a home made version of this



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Josh Millward

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Re: Distance between electrical and audio cables
« Reply #21 on: January 16, 2015, 12:50:25 pm »

Mike, I know your the power guy.  What do you recommend for this issue / what do you use ?

it seems the video link i posted is a home made version of this



That, right there, is one product that will never, ever receive a UL Certification or UL Listing.

It is but a bandaid for masking the real problems, which are typically things like Pin 1 issues in the interconnected gear, or missing ground connections.

I have been running from the position of ground everything, completely, all the time; and run it all from one source of AC. If this is not possible, use audio isolation transformers to provide galvanic isolation for things operating on different sources of AC. The result is that I never have hum or other weird noises to eradicate from my systems.
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Josh Millward
Danley Sound Labs

Nate Armstrong

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Re: Distance between electrical and audio cables
« Reply #22 on: January 16, 2015, 03:12:38 pm »

Often my shows are to small to run a distro. so i use house power.. Most of the time i have zero hum.. but every now and then i do.
It drives me crazy.. CRAZY


it is often
1) different ground potentials on different power outlets though out the venue.  Even when i pull FOH and all PA from the same backline/ stage area power sources. ( example  multiple outlets on the backwall of the stage)

2) older guitar amps like the fender twin reverb
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Mike Sokol

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Re: Distance between electrical and audio cables
« Reply #23 on: January 16, 2015, 05:14:58 pm »

Often my shows are to small to run a distro. so i use house power.. Most of the time i have zero hum.. but every now and then i do.
It drives me crazy.. CRAZY

it is often
1) different ground potentials on different power outlets though out the venue.  Even when i pull FOH and all PA from the same backline/ stage area power sources. ( example  multiple outlets on the backwall of the stage)

I've seen a number of otherwise properly wired back wall outlets where a few of them had the ground and neutral wires swapped. They test as normal except when under load. Then any voltage drop that should happen on the neutral will now occur on the EGC ground instead. So a big bass note or kick drum which normally causes a few volt drop on the neutral will induce this voltage on the EGC ground, which can produce a GLVD (Ground Loop Voltage Differential) resulting in shield current which causes ground-loop hum that is modulated by the normal current fluctuations of the power amp. I've been messing around with this in my head and on my test bench and call it GLID (G-L-I-D) for Ground Loop Induced Distortion. It sort of sounds like fuzzy bass that has a 60 Hz hum modulating the fundamental note. I can make it happen on my test bench easily enough under forced conditions, but I've been thinking about a simple demonstration that could be done in a room full of listeners with normal powered speakers. GLID can be caused by any miswiring that creates ground loop current and hum under varying amplifier load, but I think the swapped Neutral-Ground wires almost guarantee it will happen.

It seems crazy that someone could swap the ground and neutral wires accidentally, but it's not obvious with casual testing and doesn't create immediately hazardous conditions like an RPBG (Reverse Polarity Bootleg Ground) does.

Sorry for my custom acronyms, but electrical engineering and code books really don't explain how this all works, so I've got to come up with my own definitions sometimes.   
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Mike Sokol
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Greg_Cameron

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Re: Distance between electrical and audio cables
« Reply #24 on: January 16, 2015, 05:37:04 pm »

I have been running from the position of ground everything, completely, all the time; and run it all from one source of AC. If this is not possible, use audio isolation transformers to provide galvanic isolation for things operating on different sources of AC. The result is that I never have hum or other weird noises to eradicate from my systems.


This is my method as well. I regularly have to run relatively remote powered speakers through the multi-room venue I do most of my work, where running power from my main PA distro is truly impractical. So I use local circuits for those remotes and slap a Whirlwind ISO1 transformer in line. No noise problems, proper AC safety ground, and a high quality transformer that doesn't saturate with hot levels with low frequencies. it's a win/win...
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Mike Sokol

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Re: Distance between electrical and audio cables
« Reply #25 on: January 16, 2015, 05:50:44 pm »


This is my method as well. I regularly have to run relatively remote powered speakers through the multi-room venue I do most of my work, where running power from my main PA distro is truly impractical. So I use local circuits for those remotes and slap a Whirlwind ISO1 transformer in line. No noise problems, proper AC safety ground, and a high quality transformer that doesn't saturate with hot levels with low frequencies. it's a win/win...

That's exactly what I do. I'm a simple man who has to do complicated things, so I use output transformers to feed all remote powered speakers, even if they're just on the other side of the same room. Since the transformers break the grounding path, the shield current drops to zero which means there's no ground loop current. And without ground loop current, there's no ground loop induced hum. 

See, a simple idea that lets you focus on more important things during setup. I HATE hum and buzz in a sound system. 
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Jay Barracato

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Re: Distance between electrical and audio cables
« Reply #26 on: January 16, 2015, 06:16:15 pm »

The thing is if the dimmers are dumping hash onto the ground it doesn't matter if you are pulling from one source or several. I think back to the hotel room that was giving me fits despite pulling everything from a single 15 amp circuit. Every circuit on the subpanel on that floor had the same problem including the hotels installed system. It turned out to be the dimmers they had installed on the room lights. You could get away with full on or full off but no where in between.

Sent from my DROID RAZR HD using Tapatalk

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Jay Barracato

Mike Sokol

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Re: Distance between electrical and audio cables
« Reply #27 on: January 16, 2015, 07:19:26 pm »

The thing is if the dimmers are dumping hash onto the ground it doesn't matter if you are pulling from one source or several.

Dimmers are evil...
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Mike Sokol
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Mike Sokol

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Re: Distance between electrical and audio cables
« Reply #28 on: January 16, 2015, 07:37:18 pm »

Mike, I know your the power guy.  What do you recommend for this issue / what do you use ?

I have a few of the HumX lifts on my test bench, and have tried them in the field. I've even tried a dead short from the hot line to their diode isolated ground a bunch of times which trips my circuit breakers without blowing up the HumX internal rectifiers. That being said, they only work on very small ground differential voltages (less than 1/2 volt AC) and tend to turn moderate ground loop hum into ground loop buzz. That's because the diodes begin to conduct on the peak of the AC cycle when they forward bias.

I think there's lots better ways to stop ground loop current induced hum than a diode ground lift. Audio isolation transformers are my #1 choice, followed by pin-1 lifts on balanced inputs. And if you can get a power distro system in a building properly grounded without contamination from building steel and such, then the previous fixes just aren't needed. Dimmer buzz is it's own kind of hell, and we could (and probably should) discuss that at some point. It's just so messy I don't like to think about it. 

However, electrical things are rarely perfect, so I like to go into battle with my loins girded in steel (how poetic). I take every kind of transformer DI and ISO box I have and put them in any predictable ground loop paths. Most of time I'm smart enough to out-think the gremlins, but I still get surprised at times. Then I put on the thinking cap and try to figure out what's happening to cause the latest hum/buzz/hiss/hash.
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Mike Sokol
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Nate Armstrong

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Re: Distance between electrical and audio cables
« Reply #29 on: January 19, 2015, 09:10:06 am »

Thanks guys, I didnt know about Iso Boxes. only DI's
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