AVPro Edge has released a USB extender kit, giving integrators the ability to overcome common length limitations. Stephen Dawson checks it out.

USB – the Universal Serial Bus – is long-lived. A quarter century ago when I was reviewing very early portable MP3 players, some actually used an adaptor for a computer’s parallel printer port in order to get a download of songs in a shorter time than the run-time of the songs themselves.

When USB 1.1 arrived and was used, it was an enormous improvement, with 12Mbps data transfer speeds.

Then came USB 2.0. That became, and in many respects remains, the de facto standard for connecting peripherals to a computer, whether USB Audio devices or HIDs (Human Interface Devices – such as mice and keyboards) or webcams. It upped speeds to 480Mbps – say, half a gigabit-per-second. That was fine then and remains so for most of those devices, but with external storage, more speed is required. So, we got USB 3.0, 3.1, 3.2 and 4.0, which pushed speeds to 5Gbps, 10Gbps and even 20Gbps.

The problem with USBs has always been short cables. Especially in the more recent, higher specification versions, the maximum “practical” length, according to Wikipedia, is around 3m.

What is it?

The AVPro Edge AC-EXUSB-3-KIT USB Extender overcomes this length limitation. You plug a USB cable into one element of the kit. It is connected to the other element by up to 100m of Cat 6A network cable, or up to 70m of Cat 5e network cable. That second element provides four USB Type-A connections for peripherals. Speeds of up to 5Gbps are promised, despite this length.

At the computer end, the Host Unit has a USB Type-C socket for connecting to the USB connection on a computer. It has ‘USB 3.2 Host’ printed on it, although lesser USB standards also work. On the other side is a standard RJ45 connector. You use the above-specified cable to connect the Host Unit to the Device Unit.

It also has an RJ45 connection for the other end of the network cable and on the other side four USB Type-A connectors rated at USB 3.2. The whole thing is prominently labelled as a “5Gbs USB 3.2 Gen-1 Extender” and “Up to 328ft/100m on 5.0Gbps”.

You plug whatever peripherals into the Device Unit.

Setting up

There really isn’t any setting up to do. Gather your cables, plug them in and choose which end to power.

A 48V power supply is included, and you can plug it into either the Host or Device unit, as convenience dictates. A switch on the Device unit allows you to select whether the power to the four USB sockets is provided by the source USB socket at the other end, or by the extender itself. I used the latter all the way through. I think calling on a computer 100m away to provide the power is a bit too much to ask.

In use

So, did the extender work? And how well? These questions proved to be a little difficult to answer definitively. Well, I can say definitively that with a 20m Cat 6A cable, the answers are yes, and very well.

But what about over 100m? The distributor provided that 20m cable and no others. And despite my dedication to my craft, I wasn’t about to go out and spend hundreds of dollars for a 100m cable that I would likely never use again.

That said, the 20m cable would seem to be solid proof of concept, and properly built Cat 6A cable is indeed specified to support 10Gbps data speeds. This extender is specified to support 5Gbps USB throughput. I would expect that the packetisation and transfer protocols would add some overhead, but 10Gbps should be more than adequate to maintain performance.

Lacking an actual 100m cable, I employed my home’s internal network cabling. The place is only a few years old and includes fibre to the premises. Near the fibre connection is a panel with four RJ45 sockets, each of which is connected to a different point in the home. I use a network switch and two of the sockets to feed gigabit network wiring to my office and to my loungeroom TV. Other gadgets in the home rely on WiFi, connecting wirelessly either to the Telstra/NBN router or to a three-pack Eero mesh WiFi system.

All that leaves two other potential spurs of network cabling. One I’d estimate at 50m or more (by the time it makes its way through the various wall cavities and to the upper level) and the other at around 40m, since it’s a bit closer to the four-port panel, and on the same floor.

With that, I started by connecting the two circuits with the 20m cable and plugging a computer into one of the terminuses and a USB drive into the other one. The computer failed to find the USB drive. So, I plugged the USB drive into one end of the longer Ethernet route, and the computer into the other, and still no connection. That’s the one I’d estimate at 50m (a bit more, actually, given the network cables at both ends between the built-in connection and the AV Pro boxes).

But when I repeated this with the likely shorter ground-floor connection, the computer immediately found the USB drive, and its performance was pretty much the same as with the test 20m cable. I asked around, and apparently, the complex within which I live was wired up with Cat 5e.

In addition, we have those tails between that circuit and the components, and of course, the actual RJ45 connectors, each of which would, I’d expect, reduce performance a little.

So given the performance was quite similar to that of the direct 20m connection using Cat 6A cable, I’d have to say that the delivery protocols employed by the AV Pro system seem to be very robust: if you have a reliable connection, you pretty much get full speed.

And what was that speed?

Well, I used three different USB-C devices, each supporting USB 3. One was a Logitech Brio 4K webcam. It worked perfectly via the extender kit with both my Mac Mini and my Windows 11 notebook.

The second was a Lacie 1TB USB-C portable hard drive. Again, it worked perfectly. Writing to the drive from my ASUS Zenbook 14 UX425 computer, whether by a direct connection to the computer’s USB connection, or via the AV Pro extender, ran at about 1Gbps (where, for clarity, the “G” is 10⁹, or a billion). Reading from the Lacie and writing to the Zenbook ran at about 6.5Gbps.

Clearly, the write speed of the Lacie hard drive was the limiting factor. I repeated this with a Samsung EVO 2TB USB-3 SSD and it sped up the computer to drive speed somewhat, while (mostly) delivering similar drive to Windows computer speeds.

“Mostly” because Windows is weird and SSDs are weird. Often, for no discernible reason, one or the other can stop and think about things for a while, slowing down the transfers. That happened regardless of whether the drive was plugged directly into the computer or was talking via the AV Pro extender.

From EVO to Zenbook, the speeds seemed to be typically even faster than with the Lacie, although I’d caution that when using a stopwatch to measuring file transfer speeds which take less than two seconds, the percentage error is significantly higher. These seemed to run at 7Gbps to 8Gbps.

For all these tests I used a 1.5Gb video file (1,633,262,592 bytes to be precise). Cognisant of the possibility of the drive or the computer speeding up through keeping the whole thing cached, I used various strategies of renaming the file, and always copying some additional bulky files in advance of the timed runs, to try to spoil such strategies.

Remember, all this worked pretty much the same whether the Samsung drive was plugged into the Zenbook’s USB-C port (actually, it’s Thunderbolt 4 with support to up to 40Gbps speeds), or into the same port via the AV Pro extender and 20m of Ethernet cable, or into the same port via the AV Pro extender and something like 40m of my home’s internal Cat 5e cabling.

I also checked with a 2020 Mac Mini which employs the M1 processor. Its Thunderbolt 3 port is rated at USB 3.1 Gen 2 at up to 10Gbps. I only used the Samsung EVO for this one. The Mac provided rather more consistent numbers, which tended to show a slight speed reduction using the 20m Ethernet cable connection, compared to a direct USB connection.

For writing to the SSD, the speed fell from 2.4Gbps to 2.1Gbps, while transferring the other way, SSD to Mac Mini, the speed fell from 2.4Gbps to 2.3Gbps. The Mac did not appear capable of receiving those sizzling fast speeds exhibited by the ASUS Zenbook.

Conclusion

There’s really nothing more to say. Some things work, some things don’t. The AVPro edge AC-EXUSB-3-KIT USB Extender just works. If you need to get USB over ridiculous distances, check it out.