XLR (balanced line level) to RJ45 - another DIY question

[david.elsbury]

Have purchased some of these off eBay - http://I.ebayimg.com/t/Stainless-Steel-Wall-plate-panel-3-pin-XLR-female-x4-1-4-6-35MMx4-socket-jack-/00/s/MjUyWDQwMA==/$%28KGrHqF,!hUE5qbS1bYSBOet7Pn7ng~~60_1.JPG

and am in two minds about how to wire them.

 

Option 1 is to wire to an RJ45 jack with 4 circuits - 4 twisted pairs with no audio grounds connected. I have had issues in the past with lack of audio grounds though. I could wire to a shielded RJ45 to use shielded CAT6 but I don't have ready access to STP cables.

 

Option 2 is to remove one XLR on each panel and insert an Ethercon - 3 circuits and common the grounds. Tidyer, etc but I would have to lose a circuit...

 

What would you do / prefer?

 

Cheers :)

David

[dbuckley]

If line level, no earth will be ok most of the time, particularly with transformers at one or both ends. Mic you probably want he earth.

[david.elsbury]

Yeah, really anticipating only line level for this one. Possibly could look at putting transformers in - would you suggest the "output" end? :) Edited November 11, 2013 by david.elsbury

[sam.spoons]

You don't say what you are using them for? Or how long a run you are going for?

[GaryNattrass]

I agree what are you trying to do as mixing telephony and balanced audio doesn't tend to go together most of the time!

[david.elsbury]

Just to have to patch balanced line level audio around a building, as a bit of a "get out of jail" card. Sometimes I am in a situation where I need to throw a couple of balanced lines across a ballroom or whatever where there are no audio patches, or if there are they are in the most inconvenient places. Maybe between 100 and 200m tops?

 

Gary, this is nothing to do with telephony, the closest it comes is the connector used...

 

This is basically a DIY version of a 'Sneak Snake' or an 'Instasnake' (Google them for more info)

 

Cheers

David

[GaryNattrass]

So why not use audio connectors as I find RJ45 not very robust for audio applications and they are easily broken!

[stevefez]

So why not use audio connectors as I find RJ45 not very robust for audio applications and they are easily broken!

From what I can tell, David is wanting to use already present cat5/6 ports and create a box that can be readily plugged directly into these giving him 3 or 4 line level tie lines.

 

David - I would go for 3 with an ethercon 'out' simply for the neatness of the box.

 

EDIT: SPAG

Edited November 11, 2013 by stevefez

[GaryNattrass]

and here is me thinking that we had come a long way from using bell wire?

 

personally I would only use telephony infrastructure for coms or data but to send four channels of audio unbalanced on a single RJ45 plastic plug is asking for trouble but I appreciate it is a cheap way of using computer infrastructure but god knows what else could be induced onto the audio lines and then come through a PA system etc?

[Oldradiohand]

Nowt wrong with bell wire. Twisted pair balanced line audio circuits will go miles along the same cable without interfering and cat5/6 cable is not too dissimilar to old fashioned multipair audio cable. Just keep the send/return balance good, transformers are probably the best to use here.

[MarkPAman]

and here is me thinking that we had come a long way from using bell wire?

 

personally I would only use telephony infrastructure for coms or data but to send four channels of audio unbalanced on a single RJ45 plastic plug is asking for trouble but I appreciate it is a cheap way of using computer infrastructure but god knows what else could be induced onto the audio lines and then come through a PA system etc?

 

I wouldn't send an unbalanced signal down CAT5, but then I'm sure David wouldn't either. The fact that he's trying to decide between 3 circuits with ground or 4 without points in that direction too. As for the plastic plug, I assume he's going to use etherCON on his boxes.

 

This is actually quite a common thing to do, as CAT5 is so cheap & often already in place.

 

My boxes are 3+earth, by the way.

Edited November 11, 2013 by MarkPAman

[Doug Siddons]

If I can hijack this for a minute just wonderd if there is an off the shelf solution to a little problem I have. My digi core has ethercons either end, if I want to use a Laptop instead of a surface is there an adaptor which would turn the ethercon into a "normal" socket so I can plug the lap in? The only thing I could find is this http://www.neutrik.co.uk/en-uk/lighting/accessories/inline-adapters/ne8ff

[david.elsbury]

Thanks all. Think I'll bite the bullet and swap out an XLR with an Ethercon.

 

Gary, would have thought with all that extensive film and TV production knowledge (by the way... your signature says "15 mins" - it's more than 15 minutes right?) you'd know that balanced line level audio travels an extremely long way with no issues. Cat5 cable has a very good, tight twist on the pairs, so as long as you wire correctly then you'll maintain the common mode noise rejection.

 

Cheers :)

 

David

[Oldradiohand]

Thanks all. Think I'll bite the bullet and swap out an XLR with an Ethercon.

 

Gary, would have thought with all that extensive film and TV production knowledge (by the way... your signature says "15 mins" - it's more than 15 minutes right?) you'd know that balanced line level audio travels an extremely long way with no issues. Cat5 cable has a very good, tight twist on the pairs, so as long as you wire correctly then you'll maintain the common mode noise rejection.

 

Cheers :)

 

David

 

About 80 miles to be precise.http://www.blue-room.org.uk/public/style_emoticons/default/biggrin.gif That's the distance of the unrepeatered reserve circuit from London to Daventry that the BBC used to use. Only equalised up to 5kHz for shortwave but still bloody impressive.

[dbuckley]

Yeah, really anticipating only line level for this one. Possibly could look at putting transformers in - would you suggest the "output" end?

 

Either end will do. You are doing what I thought you might be doing, and in large buildings the concept of "earth" is a bit variable, so keeping audio and earth separate is a wise thing to do.

 

I'd put the transformer at the receiving end, but one at each end even better. Desk line outputs are quite hardy and so will drive line quite happily over the cat5, with the transformer just cleaning the earth at the receiving end.

 

Neutrik make nice line transformers which have affordability on their side, as such things go. If quality not so important then Jaycar MA1512 just fine, and I use something even cheaper and nastier on my stage relay box. The only thing with transformers is they can saturate, and generally, cheap transformers saturate before more expensive transformers, particularly lower frequencies, so trade level for LF response and distortion, or buy more expensive transformers. Compare the Neutrik NTE1 and NTL1 specifications for level, -3dB versus +19dB at 50Hz, so if you want to transmit 30Hz you'll need a lower level again. Apply HPF for 75hz, and the handle-able levels go up.

 

E2A - with balanced and transformers, you can use all four pairs.

Edited November 11, 2013 by dbuckley