I have written about running audio signals over CAT 5/6/7 wires normally designed to carry Ethernet traffic. But is is possible to run Ethernet over audio cabling terminated with XLR connectors?
We recently moved into an old recording studio that has 4 feet of isolation between tracking room and the control room. The studio was built in the 80′s and has plenty of XLR (analog) connectivity through the wall.
I would like to put a digital snake in the tracking room and send the CAT6 cable through to the Control room – the CAT6 would connect to the Digital board. But, it is impossible to run an ethernet cable through the wall.
There are several companies that make products to pass balanced audio signals (analog xlr or digital AES) through cat5 cables passively. So could those used in reverse?
Category cable CAN be used to carry audio signals because audio frequencies are so low the cable type doesn’t really matter. The reverse is not true and trying to use old mic lines to transport data is almost certain to be an unhappy experience.
Prosound web discussion had also question touching the same topic:
Did a search on the forum… there’s plenty of results with “Ethernet” and “XLR”, but I didn’t find anything specifically as “Ethernet over XLR”.
Is anyone doing Ethernet over XLR?
Was considering something like this for network connectivity:
For a wired connection, was hoping to use an existing snake channel, instead of having to pull 150/200ft. of CAT-5/6 cable.
While you -can- do what you’re saying with the xlr/ethernet conversion, I wouldn’t recommend it. I don’t see much reason to convert from one type of cable to the other, when all you really need is a single ethernet cable run.
Unlikely to work. 10/100Mbit ethernet requires two pairs. Gigabit requires 4. Most (all?) mic cable doesn’t even meet the specs of cat3 cable which if memory serves (it’s been a long time) was the minimum for 10Mbps ethernet. Additionally, 328 feet is the spec max cable length for copper for Ethernet. That’s point to point with solid cable. Patch bays and splices unless very high quality will further reduce the functional length. Trying to use sub-standard cable over a relatively long distance is unlikely to work.
All that said of course it may work, it wouldn’t be hard to rig up a RJ45 to 4 XLR adapter and try it. Make sure you get the pairs right though. If it does work it would be interesting to know what the reliability and throughput is. I wouldn’t waste my time on it though.
The advice to bundle a couple network lines with your analog snake is good advice.
As an alternative several signal converters were also recommended:
There are plenty of devices out there that boast the ability to transfer network down a two-wire connection. All will be much more expensive then a $30 cat6 cable
Let’s dive in to the cable characteristics more closely.
Category 6 cable is designed with a specific characteristics to carry the very high frequencies used in high-speed data transmission. The cable is designed to have 100 ohms impedance and low attenuation. The cat 5 / 5e / 6 impedance is 100 ohms ± 15% or 85 ~ 115Ω (1 ~ 250 MHz CAT 6). Ethernet cabling has 4 pairs, the Green has 65.2 twists per meter, the Blue pair has 64.8 turns per meter, the Orange pair has 56.2 turns per meter, and the Brown pair has 51.7 turns per meter. This is done to spread and minimize the crosstalk influence of the individual pairs. The baud rate (not to be confused with the bit rate) of the MLT-3 for Fast Ethernet, or PAM-5 for Gigabit Ethernet will be in the 125Mhz range.
Audio cables typically have different impedance than CAT 5/6/7 and they typically have much more attenuation at high frequencies. The characteristic impedance of balanced, 2-wire twisted pair audio cable usually falls between 50 ohms and as much as 190 ohms.
In the case of AES/EBU digital audio, the standard calls for 110-Ohm cable, although it looks much like audio cable that’s been used for decades to carry analog audio.
The typical broadcast-quality analog audio cable has a characteristic impedance of 45 Ohms to 80 ohms.
If the source and destination impedance are unmatched, some of the energy being transferred from source to destination is reflected back from the destination (or wherever there is an impedance mismatch in the connecting circuit) towards the source — not a good thing, in general. Theoretically such reflections could manifest as echoes, or cause signals at certain frequencies to be reduced through cancellation.
In order to deal with impedance matching problems, the telecoms industry quickly standardised on a connecting impedance to ensure good transfer of audio signals with minimal reflections, and that was 600 Ohms. That impedance matched the first lines on telephone poles. In practice, the actual telephone cables tended to have a characteristic impedance of about 120-140 ohms. Early broadcast and recording studios also employed the 600 ohms matched-impedance principle for almost everything.
Electrically, Cat5/5e/6 is fancy phone wire with extra care to avoid cross-talk. Some but not all Cat6 is shielded; there is a plastic separator in the wire that aids in signal isolation. Ethernet cabling uses an 8 conductor cable, bit not all wires are used always. Gigabit Ethernet uses all wires. If you run 10 or 100 Mbit/s Ethernet, you need only four wires (two wire pairs) to do it.
Here is some cable technical data for Alcatel LANmark Category 6 UTP cable:
For Ethernet copper cabling when used for 10/100/1000BASE-T, the maximum allowed length of a Cat 5e / Cat 6 cable is 100 meters (328 ft). This consists of 90 meters (295 ft) of solid “horizontal” cabling between the patch panel and the wall jack, plus 10 meters (33 ft) of stranded patch cable between each jack and the attached device. It must be 100m (328ft) or less in length to be certified. It is possible a longer cable will work, but it is not guaranteed. Signal attenuation appears to be the limiting factor and a lot of Electromagnetic interference (EMI) are the limiting factors when Ethernet link works or not.
Analog mic wire is (or should be) a shielded pair and has very good frequency response (close but not quite as good as RG59 wire) and should transmit signal safely and without noise up to 250 ft. If 4 mic wires are punched down on a phone block in a metal box where all shields are grounded together and each colored pair is tied into a single mic line (1 mic wire per color set) everything should work fine.
Basically the analog mic cable consists of shielded twisted pair wires where where each wire pair has it’s own shield. This keeps the cross-talk between different pairs low and attenuates external noise that tries to get to cable. The cable is designed for low frequency use, so it’s high frequency properties are not usually as good as with CAT 5/6/7 cable (means more high frequency loss). The microphone cable is typically well shielded against EMI, so signal attenuation is usually the main limiting factor how long Ethernet signal could run over microphone cable. Typically microphone cable attenuates the high frequencies more than CAT 5/6/7 so the signal can typically successfully travel less than 100 meters before attenuating too much.
You cannot really run Ethernet with one 3 pin XLR. To run all the signals that go on Ethernet wiring, you you could at least theoretically split the 8 conductors (for wire pairs) to four XLR connectors. This can be done as described in my XLR over CAT 5/6/7
post. Basically you have two XLR-RJ45 adapters on both ends of connections, and if things work well you could get Ethernet running. Make sure you connect each twisted pair to one XLR cable, so blue & blue-white go to one XLR, orange & orange-white go to one cable etc.
If you plan to run gigabit Ethernet, you would need all four XLRs. If you are satisfied with slower 10 or 100 Mbit/s Ethernet versions, you would need only two wire pairs which means two XLRs. If the cable run is not too long and cable close enough to what is used for Ethernet, it could work. But it will cost you 2 or 4 XLR connections on your audio wiring.
Electrical Properties at 20°C
Loop resistance 81Ω/km
Insulation resistance (at 500 V, 1 min.) 2 GΩ*km
Capacitance at 800 Hz 85 nF/km
Max. operating voltage75 V
Relative velocity factor NVP0.66
Impedance (at 10 MHz) 70 Ω +/-10 %
I began testing because it could work. The 10 and 100 Mbit/s Ethernet signaling is quite robust. At 10 Mbit/s speed Ethernet has been found working over quite poor wiring, even with an four wire telephone cable even shared with phone line. So with two pairs in use at 10 Mbits/s this is expected to work for some distance, maybe not full 100 meters but some shorter distance. At 100 Mbit/s how well it works is more of question mark because 100 Mbit/s Ethernet needs better quality cable to work OK.
It seems that there are quite good opportunities for Ethernet to work over JAMAK some distance. The lower than normal Ethernet wiring impedance of JAMAK makes a slight mismatch and this mismatch causes reflections at the ends of the lines. The JAMAK cable is about 70 + -10 ohms at 10 MHz, so you might be able to work without too much issues. If those signal reflections are a real problem, the matching could bebe improved by a transverse resistor of about 270 ohms at the end of the line or at both ends.
The attenuation of the JAMAK at 1 MHz is roughly double that of the cat 3/4/5 cable and the manufacturer’s data sheet does not list a significant attenuation in the 10 MHz frequency band. Based on the quick laboratory testing it seems that at 10 MHz and higher up to 30 MHz the attenuation follows quite similar curve as CAT 5 cable but with somewhat more attenuation. I read some comments that 10 Mbit/s and 100 Mbit/s has gone OK through JAMAK up to 60 meters. When working at those speeds the most signal falls between 10 and 30 MHz frequencies (if running Gigabit the highest frequencies go up to 80-100 MHz).
I did some testing with around 6-7 meters piece 4 pair JAMAK. Running signal back and forth 4 times makes equivalent of around 25 meters of cabke. For initial testing I run one direction of Ethernet through it and other directly through normal cable. This worked well at 10 and 100 Mbit/s even though the connection were “quick dirty hack” made with Krone punch-down block and cheap quick wire connect blocks.
Longer cable testing is next step. When I found a 50 meter jamak cable with XLR connectors in stock, I decided to test Ethernet through it. 100M Ethernet seems to be going OK through it. At the ends, a class of ten meters of traditional ether cable (a red wire to the switch and two DIY RJ45-4XLR adapter cables).
To make sure connection worked I checked that connection registered as 100meg, did packet loss test with ping plus some load testing with web browsing, video streaming and speed test.
I don’t have official certifying test gear to do all needed tests to make sure how close we are to limits of reliable operation.
If you use some other audio cable, your results can be different. Basically more the cable impedance is off from 100 ohms and more the high frequency attenuation in 10-30 MHz frequency range is, the smaller distance the Ethernet connection works.
The cables designed for AES3 (also known as AES/EBU) are have characteristic impedance of 110 ohms. This impedance is very close to the Ethernet 100 ohms, so impedance matching is not expected to be any serious problem. The 110 ohms cable designed for AES/EBU are also widely used for modern analog audio applications. If you happen to have this type of cable, I expect that it will work for some distance but maybe not close to 100 meters because based on the data on the AES/EBU cables I have seen the cable signal attenuation is higher compared normal Ethernet wiring. DMX-512 applications also use cables in 100-120 ohms impedance, and they should be at least in theory work acceptably in Ethernet applications as well. I have not yet personally done testing with those cable types.
If Ethernet does not go through directly as it is, then there are options to consider pulling a new Ethernet capable cable or invest to some kind of communications adapter that can run through the cable you have. If you are looking for the converter box idea, one option is to use SDSL/VDSL type communications devices that can transport Ethernet signal over single wire pair. Those cost some money and quite often can probe the communications channel parameters so that they can use high speed on short good cable and slow down communications speed for longer and worse cable. What you get with the money you paid for those boxes is reliable communications over the given link, maybe not always the full speed but reliable operation at lower speed if faster speed does not work.