Line level audio over Cat5

[jonny_av]

Very quick question...

 

What is the difference between using 1) an audio to cat5 balun to send line level audio over cat5 and 2) simply using the copper and running line level audio straight down the cat5 cables?

 

I've done tests using both, the baluns were relatively cheap- and without opening them up, I'm assuming they are literally just converting the connectors... Unless I'm missing something?

 

Using the cable on it's own allows me to send two or more channels of audio on one cable using the different pairs - using the baluns only allows me to send a single channel.

 

So- using the copper on it's own seems the way to go, but what additional extras am I getting by using a balun?

 

Interested to hear your thoughts!

[timsabre]

The baluns will (or should) contain small balancing transformers. Over short distances with balanced line audio you don't need them. Over long distances, or if you have unbalanced signals, or with video signals etc, you do.

[Oldradiohand]

If you're going from a balanced output to a balanced input there's no need to use the baluns. just use the four twisted pairs and you're away....

[Shez]

Balun = BALance + UNbalance.

 

No need for balanced runs.

[Richard P-W]

I'd agree with Tim - over a long run, matched transformers either end would be preferred. Relying on the electronically balanced outputs of equipment can give unpredictable results.

[Shez]

Relying on the electronically balanced outputs of equipment can give unpredictable results.

So plugging a desk output in to one end of a 100m multicore and an amplifier input to the other end can be problematic?

[Richard P-W]

So plugging a desk output in to one end of a 100m multicore and an amplifier input to the other end can be problematic?

 

I'll expand on my statement. What you say is often not problematic as the multicore has individually screened pairs which reduces crosstalk between pairs and external interference when compared to a UTP Cat5 which has 4 pairs in close proximity with no shielding at all.

 

We don't know what the OP is trying to send to & from. Some lower-end mixers have "impedance balanced" outputs (generally on TRS from Aux outputs etc) which aren't really balanced at all. Running a signal like that down a long Cat5 is not something I would recommend.

[Shez]

Some lower-end mixers have "impedance balanced" outputs (generally on TRS from Aux outputs etc) which aren't really balanced at all.

You are aware that the very definition of a balanced signal is one in which the impedance in each leg is identical? Whether or not the "cold" leg is an inverted version of the "hot" doesn't come in to it. Proper impedance balancing is just as effective as a transformer in terms of meeting the requirements for a balanced output.

[david.elsbury]

http://www.blue-room.org.uk/index.php?showtopic=59536&st=0&p=485960&fromsearch=1entry485960

 

This topic I started may be of interest too :)

 

David

[jonny_av]

Thanks for all the replies so far- let me explain what I'm doing so that perhaps my question has more meaning.

 

I've put together a park wide audio system for a client who cannot afford technology such as Dante or CobraNet at this stage but wanted to have audio at various locations in his park with the ability to play jingles, announcements etc etc.

 

I built an entire system with QLab, using an external soundcard with 4 stereo outputs. Different audio is routed to the four outputs and jingles/announcements etc are routed to all outputs simultaneously.

 

So - I'm then running 2 lots of cat5 to the four locations (one is redundant) both indoors and outdoors.

 

Originally I used audio baluns - which worked fine, but then I wanted to send two channels to one zone, so I tested using the cat5 cables wired to phono wall plates - allowing me to use the pairs inside the cable to send two stereo feeds per cable. This works fine too.

 

Given that I'm running the cables at long distances outdoors, would the baluns provide any protection/advantage over simply wiring the cables to phono wall plates? The system has been in place for a year now with no issues- but I'm just interested to know if I should throw away the baluns or hang on to them!

 

I should mention that at each zone, the audio input is simply feeding a mixer/amp and a pair of speakers.

[timsabre]

Yes, you should use baluns in this situation.

If nothing else it will give you improved fault tolerance and protect equipment from stray voltages. The audio signal will also be better, though this might be imperceptible.

[Brian]

Given that I'm running the cables at long distances outdoors, would the baluns provide any protection/advantage over simply wiring the cables to phono wall plates?

 

Yes, and think about how you'll deal with lighting strikes as well.

[Shez]

Once you head outdoors, it's a whole new can of worms. Earth potential inside one building can be very different to earth potential in a different building. Isolation transformers are a very good idea for this reason.

[Brian]

What's the sites earthing arrangement?

 

I'm guessing the incoming feed is TN-C-S(PME) with each area running as locally derived TT supplies but I could be very wrong. As Ze between areas could easily be 200R that means any audio earths running between areas could carry significant fault currents.

[dosxuk]

Using the cable on it's own allows me to send two or more channels of audio on one cable using the different pairs - using the baluns only allows me to send a single channel.

 

Probably worth pointing out you can get multi-channel baluns, and baluns which terminate to screw terminals rather than RJ45 sockets, so you can wire multiple baluns onto a single piece of cable. For analogue audio, they will only use one pair per channel.