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Author Topic: Ideas for reliably sending sound over long distances?  (Read 2380 times)

Mitch Philips

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Ideas for reliably sending sound over long distances?
« on: November 10, 2015, 03:54:56 am »

Hello, I need help figuring out a way to send audio over a distance of about 1500 ft (~458m). We have two systems apart from each other that distance and we have a central "command",station if you will. Latency is not a very big deal as the systems are far enough apart that they cannot be heard by the other.

To be clear, this is audio from the board, through a cluster of matrices, that comes out the same level on the other side, except that the signal is now duplicated for both systems. The central command post is at the larger system and I need signal at the smaller system.

This is not amplifier-level signal over this distance.
This area is an outdoor mall venue, installation would not be an issue. But there are no "straight shots" directly to ether system and the line would have to travel through a building.

Budget is $7k for this job, but I was allowed a little wiggle room. I am open to any and all suggestions of how to do it.

Please give me your thoughts and suggestions. I can also answer any questions you may have to the best of my ability.

Thanks!
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Scott Carneval

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Re: Ideas for reliably sending sound over long distances?
« Reply #1 on: November 10, 2015, 06:01:52 am »

Balanced analog line level audio should travel that distance without an issue. You MAY require an isolation transformer on either end but I would try it without first.

You could convert to fiber and then back to analog at the other end but I really don't think it's necessary.


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Jason Lavoie

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Re: Ideas for reliably sending sound over long distances?
« Reply #2 on: November 10, 2015, 11:29:40 am »

Budget seems reasonable (for the first time ever on this forum!)
So as Scott says, just pull a shielded pair (and maybe a spare, or a 2-pair) and plan on maybe having to pickup an isolation transformer.

You're not likely to find a single piece of cable that long, so plan a few strategic splice/test points along the way

Jason
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Joseph D. Macry

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Re: Ideas for reliably sending sound over long distances?
« Reply #3 on: November 10, 2015, 02:13:04 pm »

Balanced analog line level audio should travel that distance without an issue. You MAY require an isolation transformer on either end but I would try it without first.

You could convert to fiber and then back to analog at the other end but I really don't think it's necessary.

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Here is one reason to use fiber optic (if it is in budget) rather than a copper line. That is that the long copper line can pick up induced spikes from nearby lightning strikes.
I recently worked a football stadium where the visitors'-side amp rack was fed by a 1300-foot long (underground) copper line, but nearby lightning strikes (not a direct hit) kept killing the DSPs on either end of this line. Perhaps an isolation transformer might have helped, but the field already had spare fiber lines going from side to side. So we got a fiber-optic encoder/decoder (Extron FOX AV series transmitter and receiver) to send audio around the field. Downside: The tx/rx set cannot send a contact closure, so the power sequencing line (that tells the visitors' side rack to come on) is still copper and has killed a couple of sequencing units (SurgeX brand).
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Joseph Macry,
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TJ (Tom) Cornish

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Re: Ideas for reliably sending sound over long distances?
« Reply #4 on: November 10, 2015, 02:30:35 pm »

Balanced analog line level audio should travel that distance without an issue. You MAY require an isolation transformer on either end but I would try it without first.

You could convert to fiber and then back to analog at the other end but I really don't think it's necessary.


Sent from my iPhone using Tapatalk
IMO isolation transformers are not optional.  Any time you're bridging equipment connected to different electrical services or going more than a couple hundred feet outside, isolation transformers are necessary to break ground loops and materially isolate equipment inputs and outputs from lighting-related issues that Joseph mentioned.  Fiber is great too, but more costly.
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David Buckley

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Re: Ideas for reliably sending sound over long distances?
« Reply #5 on: November 10, 2015, 02:37:30 pm »

IMO isolation transformers are not optional.

This.  Heed these words.

Edited to add: and if you go fiber, which is not a bad idea, make sure it isn't metallic sheathed fiber, otherwise you are back to square one, and have to worry about mains-induced potential differences along the metallic sheath.
« Last Edit: November 10, 2015, 02:40:43 pm by David Buckley »
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Mitch Philips

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Re: Ideas for reliably sending sound over long distances?
« Reply #6 on: November 10, 2015, 02:51:27 pm »

I'm not too worried about lightning as this mall area is right outside of a theme park in Southern California where there are several taller metal structures around that would probably get struck sooner than the cable or even around the cable.

I was definitely planning on getting an ISO transformer if I were to run a copper line. We have had some interference issues in the past running shorter runs of cable, presumably due to the many neon lights around the area and an ISO transformer seemed to solve these issues.

I will look further into fiber optics to see if it is a viable option price-wise and longevity-wise.

Thanks for the tips so far! I really appreciate it.
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ProSoundWeb Community

Re: Ideas for reliably sending sound over long distances?
« Reply #6 on: November 10, 2015, 02:51:27 pm »


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