Audio over cat 5??

[lonfire]

hi guys,

I'm looking at doing something similar.. was going to install CAT5 all over the building and use it to send feeds (video/audio) to various places in the building.. but after looking at the costs of baluns and stuff I think I might just buy some cheap mic cable (and cheap video chable) and run that instead..

 

rgds

chris

[The Magus]

Have a look at this site Aviom - digital snakes. It's not a cheap solution by any means (unless you're using very long cable runs) however it provides an elegant and lightweight solution if you're using a lot of channels over a long distance (up to 500 feet). They also have an interesting personal monitor system which integrates with the digital snake. I think it's capable of transmitting 64 channels at 24bit / 48kHz using UTP cable. I've thought very seriously about getting one, but decided to wait until they produce a 96k version with a Yamaha format input card!

[james jag]

you know what a XLR is ? know how to wire one ? pin 1 screen, pin 2 +, pin 3 -, the point is the screen, unless you are converting this signal to digital format it will be crap, analog signal cables have a certain inductance and capacitance at the frequency range for audio, cat five cable is made for data transmission at much higher frequency range than audio, and it is not screened, on the plus side you might pick up talk sport radio :)

[david.elsbury]

you know what a XLR is ? know how to wire one ? pin 1 screen, pin 2 +, pin 3 -, the point is the screen, unless you are converting this signal to digital format it will be crap,

I'm sorry this comes across harsh, but you are just plain wrong (and I've noticed that some of your other posts put across mis-information too) :blink:

 

It has nothing to do with the screen. All the screen does is stop a particular type of interference from getting in. The twists in CAT5 cable are better than the twists in mic cable... and because audio is balanced, it's the tightly twisted pair that primarialy rejects interference.

 

The signal will not be "crap" if you run analog audio down CAT5 cable. I have sucessfuly sent audio down this cable before. However, as many others have said above, it's better to send line level audio, than mic level.

 

analog signal cables have a certain inductance and capacitance at the frequency range for audio, cat five cable is made for data transmission at much higher frequency range than audio, and it is not screened, on the plus side you might pick up talk sport radio :huh:

 

Somebody needs to read up on the sites mentioned earlier... plus, the only way you'll pick up radio, is if the line is / becomes unbalanced.

 

I'll say it again, it's mostly the tightly twisted pair, and the fact that the signal is balanced, that means that there's no interference.

 

Sorry for the rant guys...

Night, David.

[Ben Langfeld]

Plus, there is no such thing as "XLR Cable" :blink:

[Simon Lewis]

analog signal cables have a certain inductance and capacitance at the frequency range for audio, cat five cable is made for data transmission at much higher frequency range than audio, and it is not screened, on the plus side you might pick up talk sport radio :blink:

 

Just to add to David's post, characteristic impedance does not play a part in audio frequency systems, unless the cable length is in the order of many kilometres.

 

Admittedly, if the output stage of the sending device cannot drive the inherent cable capacitance, slew rate at high frequencies may be compromised, but that's why you'd use a good quality desk or graphic to drive your returns snake...

 

I have often used screened "data cable" for audio installations. It works perfectly. The reason I tend not to use CAT5 is the lack of a screen where electrostatic screening is needed, or the 0V for a phantom power supply is needed.

 

Incidently, the different pairs in CAT5 have different lay lengths.... a rather cool piece of design ;-)

[robloxley]

You should be able to get something like FST for about 25p/m

Given that the majority of the costs of running lines is in the labour to pull & terminate the cables, I can't see that you'll save much and risk problems

[james jag]

about what I don't follow the general mass of thinking and my post's some times can not be read clearly but that does not mean that I have a point that is relevant :blink:

 

Somebody needs to read up on the sites mentioned earlier... plus, the only way you'll pick up radio, is if the line is / becomes unbalanced.

I'll say it again, it's mostly the tightly twisted pair, and the fact that the signal is balanced, that means that there's no interference.

 

the part of my last post about picking up talk sport radio was a joke :D , sometimes people can post something funny rather than focusing on what people said or didn't say

 

as for the screen issue their are many ways of sending audio, but seeing as you seem adamant @ telling me I'm wrong I look forward to all new audio cables being made out of stranded cat 5, and as you clearly doubt my tech knowledge, I will say last year I must have manufactured at lest 150km of screened audio cable :huh:

[Simon Lewis]

James,

 

Although I think it's David's post you are referring to, permit me to add a response.

 

I'm certainly not calling your technical knowledge into question per se, but I'm sure you'd agree that discussions on technical issues should be factually correct. After all, this forum (which I have grown quite fond of over the past year!) attracts everyone from pre-teenagers just getting started to those who are the recognised experts in their field. Accuracy is therefore a pre-requisite, and the greater our knowledge base, the greater is our responsibility for ensuring what we contribute is true.

 

Posters may have a PhD in astrophysics or have just designed the latest live digital desk, but if the written content they contribute is incorrect, others will quickly pick up on it!!

 

Regards,

 

Simon

[dbuckley]

You guys can argue your astrophysics all you want, but if you do some work in the City of London, you'll notice a fair few mic feeds going across the building's structured wiring, and it works just fine.

 

The scenario is that firstly, the buildings are flood wired with Cat5, and secondly, traders often have a "morning meeting" (often around 7:30!) where the head trader and guests outline the days expected excitement. The trend in trading floors is for them to be quite big, 1000 desks on a floor is not uncommon these days, go take a look at Deutche Bank's new building, its deep, wide, and the trading floors are flat for the whole area. Anyway, the head honcho and his boys have a mic or two, and they are plugged into the cat5. The audio goes into the intercom system, and head honch presses a button, and all his boys intercoms light up on his mic. He then speaks. He may also be talking to several different locations in several differend t countries, and he may have a reverse path for questions too. All fun stuff.

 

So, Cat 5 and mics = no problemo.

[Bobbsy]

Out of curiousity, does that stuff in the Deutche Bank building actually travel at mic level?

 

I've done similar (though smaller) installations using flood wired CAT5 for intercom purposes, but the signal was always boosted to line level in an intercom box before it travelled around the system.

 

At line level, I have no qualms about using standardised CAT5 for interconnects, but have always been to nervous to use it at mic level. Indeed, even with ordinary audio cabling, I tend to try to boost locally to line level wherever possible rather than use long runs at mic level.

 

Bob

[mackerr]

You guys can argue your astrophysics all you want, but if you do some work in the City of London, you'll notice a fair few mic feeds going across the building's structured wiring, and it works just fine.

 

The scenario is that firstly, the buildings are flood wired with Cat5, and secondly, traders often have a "morning meeting" (often around 7:30!) where the head trader and guests outline the days expected excitement. The trend in trading floors is for them to be quite big, 1000 desks on a floor is not uncommon these days, go take a look at Deutche Bank's new building, its deep, wide, and the trading floors are flat for the whole area. Anyway, the head honcho and his boys have a mic or two, and they are plugged into the cat5. The audio goes into the intercom system, and head honch presses a button, and all his boys intercoms light up on his mic. He then speaks. He may also be talking to several different locations in several differend t countries, and he may have a reverse path for questions too. All fun stuff.

 

So, Cat 5 and mics = no problemo.

What makes you think that the audio on those CAT5 runs is mic level? The intercom station that has the mic attached boosts the signal to line level before it gets distributed. Chances are it is a matrix routing system like RTS Adam, Clear Com Matrix, or Reidel Artist. All of these involve pretty sophisticated audio processing and routing, and they can all run on CAT5 cabling. They can also run on coax. When running on CAT5, they may be routing digital audio, or they may be using one pair for send, one pair for return, and one or two pairs for control data. I have installed just this kind of system on a trading floor in NYC and London. When the desk in NY talks to the desk in London, do you think mic level magically makes it through the trans Atlantic fiber route?

 

Mac

[Bobbsy]

That's what I was trying (not so clearly) to say, Mac.

 

BTW, I notice you don't mention Trilogy Communications on your list of intercoms...if you haven't tried them you ought to...they're very popular in the UK TV industry and make very nice, flexible, easy-to-configure kit. (Which incidentally is designed to work over CAT5.) Nice people to deal with too...

 

Bob

[mackerr]

That's what I was trying (not so clearly) to say, Mac.

 

BTW, I notice you don't mention Trilogy Communications on your list of intercoms...if you haven't tried them you ought to...they're very popular in the UK TV industry and make very nice, flexible, easy-to-configure kit. (Which incidentally is designed to work over CAT5.) Nice people to deal with too...

 

Bob

I'm not, in fact, familiar with Trilogy. Being based in NY I mostly get to see what's here. Over here Clear Com has been the longtime standard of live performance comm, and RTS the TV standard. I don't think Clear Com is getting much traction in TV, but RTS and Reidel are making inroads in the live side. Reidel's high profile presence at the last couple of Olympics hasn't hurt them. :(

 

In any case I would still avoid mic level over CAT5.

 

Mac

[dbuckley]

What makes you think that the audio on those CAT5 runs is mic level?

Because I installed it?

 

I know exactly how city technology works, or I did up till mid 90s, which is when I left the City. I have been there and done it all, and in spades.

 

RTS make intercom systems, as do Clear-Com. But the term "intercom" covers a wide variety of systems, including some very big and expensive bunnies indeed. I looked up the RTS Adam, it tops out at 1000 ports, which sounds a lot for an intercom, but for a trading floor application its a low number..

 

Below is a picture of an IPC MX station, which attached to the IPC MX switch, which is what I had the mics interfaced to, Back then this was the muts nuts of trading intercoms, doing everything a phone does, has full conference bridging, does everything the speakerbus does, and everything the the hoot 'n holler does to boot. The architectural limit per switch is 16000 ports, and you can link switches either for more ports, and/or for location transparency. The systems you mention are not in the same universe as this stuff, so forgive me for being nonplussed when you throw these names around.

 

Essentially, the trading floor mic (which is a real mic, SM58 or thereabouts, but with the cable terminated in Cat5 connector, and the signal going through a lot of Cat5) went into a preamp to line level, and was then input as a balanced line feed to the switch. It then just becomes a "line" which has the capability of being presented at any station on the system. You can access it at a station by either having it as a "presentation" which effectively means you press a button, and the buttons are labelled (on these particular stations) on an electro-luminescent display which labels each button, and you can have lots of pages of buttons. Press the button, you get the line. or through programming one button on one station can activate and deactivate the line on any station its programmed to do so on.

 

This is very cool, impressive and expensive technology. As well as very fault tolerant. Being old tech, this didnt connect up over Cat5, but used an RJ21 connector per station (50 pins) cabled down to the switch (several full height racks worth) in the data centre. More inportantly, this is the first line tool that traders use when gambling your pension fund, so it has to work and work well.

 

Of course as to how you get from London to the more than a dozen other countries on the WAN? Well, for hoot and linking (ie persistent ciruits) the the audio comes out of the MX as 4 wire and then goes to codec module on a Timeplex TDM. Though that was then, there must be much better ways available now, not to mention Timeplex must be extinct.

 

http://www.ipc.com/articles/13/000-21.jpg

 

Update: Given that this was all a long time ago, I may have got my locations confused, so it may have been a BT traders phone system rather than an MX, or even something else, but I was there and we used mic level signals over Cat5. I can remember the inspiration for the idea; at Phillips and Drew they had (from well before I arrived there) a SM58 on one of the floors which was connected over the structured wiring system, but that was pre Cat5. Their structured wiring was ethernet AUI cable, which had three twisted data pairs, and two single cores for power, all with an overall screen, with 15 pin D types on the end. Everything got shoved over this cable, ethernet, printers, and... a microphone. The only installed vertical cablie to my memory was Thick Ethernet (this was a while ago) and telecoms punch panels, so I guess it was then patched to CW1308? I can't recall if there was a preamp in the patch room. I didnt really have anything to do with voice comms or dealer systems there. Anyway, so I figured if it worked there over that oddball cable, perhaps it would work over Cat5...

 

David Buckley, ex-city-telecoms and networking guru scumbag contractor.

 

Out of curiousity, does that stuff in the Deutche Bank building actually travel at mic level?

Thats not quite what I said, I used the Deutsche Bank building as an example of a building which must still be there, however I didnt fit anything in that building, they were beginning to fit it out as I left the City.

 

At line level, I have no qualms about using standardised CAT5 for interconnects, but have always been to nervous to use it at mic level. Indeed, even with ordinary audio cabling, I tend to try to boost locally to line level wherever possible rather than use long runs at mic level.

Agree. It works at mic level, but I'd rather have line level, just on principle.