Commercial boxes designed to carry analogue audio over shielded Cat5e cable almost always have four sockets on board — obviously, it makes sense to use all four pairs of wires that are available. So if you want a smaller box with only two connectors, a spot of DIY will be required...
I’m looking to use Ethernet cable to connect a couple of balanced audio signals on XLR connectors over an extended distance. I’ve seen commercial breakout boxes with four XLRs, but I only need two. I thought I’d found a solution (for DMX lighting connections) but the two XLRs were wired in parallel, so it isn’t suitable. Are you aware of anything that can convert a pair of XLRs to an RJ45 socket and back again?
SOS Forum post
SOS Technical Editor Hugh Robjohns replies: All those commercial products have four XLRs because there are four pairs of wires in an Ethernet cable. As these can pass four balanced signals simultaneously, it makes little sense not to connect them all up, so if you don’t want to buy four‑channel breakout boxes, you’ll probably have to go the DIY route. However, the cable‑mounted ‘inline’ RJ45 sockets I’ve seen aren’t very robust, and I wouldn’t recommend making tails with two XLRs wired into an inline RJ45 box.
A better approach would be to make a bespoke breakout box with two XLRs and a Neutrik etherCON RJ45 socket. This would be robust, do exactly what you require, and be easy to build. My favoured solution for this kind of breakout box is the Canford Audio Universal Y‑Piece Box (https://sosm.ag/canford-y-piece-box), an unbreakable hexagonal ABS box with three holes for any Neutrik D‑size connectors. Any metal or plastic box could be used, but I’ve found these particularly easy to work with and extremely reliable. You simply wire the three connectors together with short lengths of cable, slot the connectors into the holes, and screw the lid down.
As long as you stick to the defined colour pairs and wire both breakout boxes the same, you can use whatever pin variants you like.
The RJ45 wiring standard uses the blue/white wires as channel 1 (pins 5/4) and the orange/white wires as channel 2 (pins 1/2), although the pin use varies with the EIA/TIA standard used. The 568B standard, which is common in the UK and US, is as I’ve described above, while the 568A standard that’s more common in Europe uses 5/4 and 3/6. But as long as you stick to the defined colour pairs and wire both breakout boxes the same, you can use whatever pin variants you like.