AES72

[Bryson]

I came across my first product with AES72 ports on it today.

Details are thin online, but as far as I can tell AES72 is a standard for 4 channels of analog audio on RJ45 connectors.  I think there's also a digital audio version (8 channels of AES3 style) - but the standard is locked beyond a paywall I don't care to pay for right now.

The product I was looking at had a mix of digital and analog audio ports all on RJ45s.  I can see the argument in terms of connector density, but can't help but feel we used to have different connector types for a reason...not sure I love everything being on RJ45.     (And, I dont much like "regular" RJ45s anyway.)

Thoughts?

[alistermorton]

I doubt the AES port would like POE up it, for example (nor would DMX ports for that matter).

[Robin D]

I agree. Pick up a cable and it traditionally told you it's function. All my 3 pin DMX XLR's are marked as such. My concern is are there any risks to the equipment of connecting the wrong types together? The typical operating voltages are quite different. A line level input is typically around 1v, DMX is about 6V, Microphones are much less. AES operates at 7V I believe with AES72, POE and phantom power all at around 48V. I am always very carefully now to cross check connections before power up, but if all the connections are RJ45's what's to stop you putting 48V into a microphone preamp or on your DMX line? 

Edit to add, with a long background in IT, we have already had that problem with Ethernet and Token Ring on the same site. Fine that you can use coloured patches for differing functions, but it relies on people knowing and abiding by the site code. How long before someone has to use the wromg colur patch as they haven't got the right one and need it live 'Now'.?  

Edited May 16 by Robin D
Add info about data lines

[richardash1981]

Google found me the draft for comment:

https://www.aes.org/standards/comments/drafts/aes72-xxxx-190215-cfc.pdf

and a handy table:

What it boils down to is that anything which uses the coloured pairs in CATx cable is "AES72 compliant" provided it prints one of the above labels by the port. However it will only work (in the main) with matched types each end (further on in the document is a table of all the possible combinations and what comes out where!).

I was amused to read:

Quote

CAT cables should only be spliced with compression based splices specifically designed for this purpose.

[...]

Providing strain relief by tying the two cables together in a knot as if they were rope does not legitimize this approach.

😀

[J Pearce]

I've done all sorts of audio and DMX (and RS232 and others) over CAT5/6. It works well and uses flexbile infrastructure.
Ratsound make the RAT-CAT boxes, and there are now cheaper versions on the market. Clearcom have used RJ45 connectors for their analogue 4 wire ports for many years now.

The more sensibly chosen pinouts avoid POE issues (and proper POE has handshaking to limit fallout), but users should be wise to the risks of crossplugging in any infrastructure where different protocols use the same connectors - this is no different to party line comms (or 12V PAR16s) on XLR3 being crossplugged with audio cabling, or XLR4s being both comms headsets and scroller/wheel cabling.