Installs Signal cables and power...

[techietim]

Okay, so I'm going to assume that most know the rule about not putting signal cable next to power cables wherever possible.

A little while ago, one of the techs at the church designed and built a platform for the music group with built in floor channels for cabling and power to the various areas.
Over all it's really very clever, except...(bet you didn't see that coming )

Me and another tech from the church (professional electrician) took up some panels to relay one of the XLR cables for a vocal patch. It was then we discovered how close the power cables and signal cables are together.

The power cables are literally on top of and side by side with the signal. Whilst all signal cables are balanced (thankfully) this is obviously not great or good practice..?

Can anyone suggest a fix that would help this and make it better without major redesign?
It rarely causes a problem but it's really not good and hoping no one else will ever see it

Thanks!
Tim

 

[josh88]

If it's not causing problems why mess with it? It doesn't sound like there is a quick fix, you'd have to take the platform out and get under it to run new stuff or cut a new channel in the top, snake the old out the way it came and run in the new channel. It all depends on how the guy made it. Probably not difficult to change but still probably a bit of a hassle if it hasn't caused a real issue.


Via tapatalk

 

[techietim]

If it's not causing problems why mess with it? It doesn't sound like there is a quick fix, you'd have to take the platform out and get under it to run new stuff or cut a new channel in the top, snake the old out the way it came and run in the new channel. It all depends on how the guy made it. Probably not difficult to change but still probably a bit of a hassle if it hasn't caused a real issue.


Via tapatalk

Yeah - it can be left as you say, it's nothing urgent...yet! I was just trying to find out if anyone did have a magical quick fix!

The way the platform works is basically that is has the main supporting joists underneath the board to keep it secure then some panels of the flooring lift up and the cable is run sort of in between the joists but more specifically made channels. It's pretty well designed in all honesty, except for that.
What should have been done was to make two channels apart from each other - one for power and one for signal? Maybe that would be the fix (as you said) if we ever needed it...

 

[FMEng]

It is good practice to keep different signal levels and power separated. That being said, in my almost 40 years of messing with audio, I can't say I have ever had a problem of noise from a power circuit being induced into a cable by proximity. I'm sure it happens but not all that easily, so I wouldn't worry about it.

If anyone has any stories of experiencing this, I would love to learn more. To keep this scientific, let's not muddy the waters with ground loop problems. Stories about noises from cables being too close, please.

 

[gafftapegreenia]

If I had to keep all power and signal cables separate corporate jobs would sure suck a lot more.


Sent from my iPhone using Tapatalk - now Free

 

[avare]

Okay, so I'm going to assume that most know the rule about not putting signal cable next to power cables wherever possible.

Festivals, etc have runs of 100' with power, line level and microphone level cables beside one another.

Andre

 

[DuckJordan]

Just did a show where power and signal cables were literally in the same snake, this is an a level national tour. If it ain't broke, don't fix it.

 

[Footer]

Should not be a problem if everything is sheilded. All of my wedges are hooked up via one cable that carries power, data, and signal in one jacket. Cable is Meyer designed. Running power and signal together will cause issues is really a urban legend. If you have good sheidling you will never have an issue. In our smaller room our FOH snake runs through the lighting grid next to tons of lighting cabling and there is no issue. Now, if dimmers are on the same power SUPPLY as audio you have issues, but no reason to keep power and signal separate.

 

[MarshallPope]

The only proximity issues that I've had have come from a laptop transformer sitting near mic cables. As a general rule, I try to keep power and mic and line cables all separate, but if they mingle together, oh well.

 

[JD]

Just watch out for speaker lines and mic lines being run together! Ultrasonics is not an urban legend and can take out a lot of equipment before being uncovered! (other then the strange pegging of meters.)

 

[FMEng]

Should not be a problem if everything is sheilded. All of my wedges are hooked up via one cable that carries power, data, and signal in one jacket. Cable is Meyer designed. Running power and signal together will cause issues is really a urban legend. If you have good sheidling you will never have an issue. In our smaller room our FOH snake runs through the lighting grid next to tons of lighting cabling and there is no issue. Now, if dimmers are on the same power SUPPLY as audio you have issues, but no reason to keep power and signal separate.

Coupling between cables isn't a complete myth. Shielding is only partially effective, which is why the circuits must be balanced. Try an un-balanced mic line some time. Just turn off the phantom power and ground pin 2 or 3 on a dynamic mic and it'll be an education. But, then the common mode rejection of balanced inputs isn't perfect either, which is why shielding is also applied. I think the CMRR performance of balanced inputs has improved greatly since about the mid 1990s. Neil Muncy and the Audio Engineering Society educated a lot of lazy manufacturers, and purpose made input stage chips made good circuits cheaper to make.

Consider that balanced audio is why telephones work. They depend upon miles of completely un-shielded, twisted pairs that often hang below power lines on the same pole. Balancing the circuit has worked miracles for more than a century.

 

[Chris15]

Yeah, I've had noise induced in audio lines before. Might have something to do with them running down a cable tray that was half a metre from the building's main switchboard...

 

[Dan0010]

i was working with an electrician once running some audio and video cables and I mentioned that we need to keep the power and a/v cables separate (balanced cables and shielded video) he told me that it only mattered if it was high voltage (like 408 coming off a branch etc (paraphrased from what I remembered) ) and if it large bundles of a/v cables.

not sure how true it is but we ran the cabling next to each other and didn't have any problems.

 

[MNicolai]

Short answer to the OP is if you don't hear a problem, don't worry about it. Short distances of mic or line level wiring next to power is unlikely to produce an audible effect. Long distances, such as a hundred or two or three hundred feet, make things more dicey.

Power cables in your platforms aren't likely to be carrying all that much current, and not sustained for any substantial length of time. If you were about to tell us that your A/V cables were run in a conduit 6" from a conduit carrying supply wires out to several branch panels, then there's a better chance you'd want to move those A/V cables somewhere else.

Longer answer is...

In a tour, temporary, or portable cable situation, it's not a big deal if cables get run on top of each other. If they do, and if you encounter a noise problem, you can route cables differently with relative ease. In an installation, where the conduits installed may be installed that way for several decades, signal level separation of wiring becomes a more substantial factor. If you should encounter noise issues in your systems after installation only to find that your power transmission conduits were installed 8" away from your mic level conduits, you could be stuck with that noise indefinitely unless you choose to install new conduits and wiring (translation: $$$$, to the tune of tens of thousands of dollars).

I'd be lying if I told you that proper signal level separation was always necessary to prevent noise coupling. It's only one arrow a system designer has in their quiver. Another is putting the A/V systems on isolated, insulated ground power distribution. Another is choosing equipment and installation methods that don't unintentionally compromise those cable separations and clean grounding schemes. A couple minor violations here or there is unlikely to produce a catastrophic noise issue. Last thing an installer or a paying customer wants is on Day One after the system is installed to find out that there's a major noise issue in the system. Worse yet, tracking down the source of the noise could cost several thousand dollars, and then mitigating the issue could be an additional chunk of change somewhere in the territory of five digits.

Therefore, we separate signal levels. It's not our only measure against unwanted noise and interference, but it's a valuable one. Especially given the extreme costs of mitigating issues after a system has been installed, if proper signal level separation of conduits and clean power schemes have not been adhered to.

i was working with an electrician once running some audio and video cables and I mentioned that we need to keep the power and a/v cables separate (balanced cables and shielded video) he told me that it only mattered if it was high voltage (like 408 coming off a branch etc (paraphrased from what I remembered) ) and if it large bundles of a/v cables.

not sure how true it is but we ran the cabling next to each other and didn't have any problems.

If I had a nickel for every time I worked with an electrical contractor who thought they were experts at A/V, I'd be a rich man. It's hard enough just finding electrical contractors or engineers who understand why our grounding schemes for audiovisual systems are what they are, but that's not really our problem if they do or not. What is our problem is if a system gets installed with noise issues and we have to devote weeks of labor and tens of thousands of dollars into resolving the issues after the systems are installed.