Sonnect SoundWire

This clever cable is as smart as it looks!

Back in February 2022, I reviewed a superb little audio tester from a start‑up company called Sonnect. Based in Italy, Sonnect are the brainchild of David Scorteccia, a professional live‑sound engineer working in the UK. I was very impressed with the design and engineering of the Sound Bullet and I remember talking at length with David about other potential products at the time — so I was very pleased recently to be asked to evaluate the company’s second product, the SoundWire.

Nearly three years in development, the SoundWire is equally innovative as the Sound Bullet in solving a perennial problem very neatly and elegantly. In essence, it’s a high‑quality, two‑channel, plug‑and‑play USB‑C audio interface/D‑A converter, providing a stereo audio output from laptops, tablets and smartphones. So far, so normal — but this product isn’t a bulky box, doesn’t need external powering, provides balanced line‑level audio on XLRs, and fully protects the source against accidental application of phantom power. In fact, it looks like nothing more than a simple adaptor cable, completely disguising the sophisticated electronics within.

The Problem

I’m sure we’ve all been in the situation of needing to get audio out of a laptop and into a mixing console. The usual options are either to take the output from the laptop’s built‑in soundcard via a 3.5mm mini‑jack in the headphone socket, or derive digital audio via a USB port. The analogue route is simple but often suffers low‑quality audio, intermittent connection problems, and potential grounding issues. And, while a direct connection from laptop to mixing console is possible using a mini‑jack to dual‑XLR ‘bodge cable’, it only needs the accidental activation of phantom power on those mixer channels to destroy the laptop’s audio circuitry — which really isn’t good for client satisfaction!

So, to be safe, it’s essential to connect the laptop via some form of isolation transformer, and that means either a stereo DI box or a two‑channel line‑isolation box. This guarantees phantom‑power protection for the laptop (as well as, conveniently, balanced audio connections back to the console), but it needs another box or two and more cables and adaptors, so it soon starts to get a bit bulky, cumbersome and expensive.

Alternatively, using a USB output needs some form of dedicated USB audio interface to perform the required D‑A conversion. That usually means another bulky, expensive box, and most USB interfaces, at least for Windows devices, expect specific audio drivers to be installed. Moreover, it remains necessary to use DI or line‑isolation boxes to provide phantom‑power protection, this time for the USB interface itself.

Either way, it’s always a complete faff to set up, with lots of adaptor cables, bulky interface boxes, and potentially multiple points of failure and confusion. The SoundWire addresses all of these issues with an incredibly simple and totally straightforward solution, which is no more difficult than plugging in a cable.

The SoundWire Solution

The SoundWire cable itself weighs just 140g and measures roughly 2.8m overall: 2.3m from the USB‑C connector to a plastic Y‑splitter joint, with the separate XLR output tails adding a further 0.5m. In other words, it’s more than long enough to run from a laptop placed alongside a console directly into its rear‑panel inputs, or a presentation podium down to a stagebox on the floor, without needing XLR extensions. One cable, three plugs: job done!

The USB‑C connector is slightly longer than most, to accommodate the (up to 192kHz) D‑A converter.

While USB‑C is the modern standard, there are a lot of legacy USB‑A ports still out there, so Sonnect offer a compact USB‑A adaptor as an optional accessory, and I’d highly recommend acquiring one for use with the SoundWire. The USB‑C plug (which has gold‑plated pins) slots neatly into this adaptor, forming a robust and reliable connection and looking much like an ordinary, if slightly chunky, USB‑A plug. The USB‑C connector itself is a little longer than usual, and that’s because inside is a teeny‑tiny surface‑mount D‑A converter (an ESS 9272 Sabre DAC), along with all the associated support circuitry. This is directly bus‑powered, obviously, drawing just 100mA, and the converter supports all sample rates up to 192kHz, with word lengths up to 32 bits. It’s also fully class‑compliant so doesn’t need any drivers, regardless of the computer host. It is literally a case of plugging in, letting the computer recognise it, selecting it as the computer’s desired audio output destination, and that’s it.

At the opposite end to the USB‑C plug is a pair of Neutrik XLRs, again with gold‑plated pins. There’s technology hidden here, too: each XLR contains a custom, miniaturised transformer to balance the output and prevent phantom power reaching the electronics. The XLRs are clearly identified as L and R on a blue ring between the shell and strain relief.

The line‑level analogue outputs are on XLR plugs, and the device is protected from the application of phantom power from a mixer or preamp.

The wiring that links the three plugs (and their electronics) is protected within a tough, 4.5mm, blue, woven‑nylon sleeve, and it is clear that this product has been designed by somebody with real‑world experience, because an elastic toggle is permanently attached to the Y‑splitter, and this wraps around the coiled‑up cable and clips into a slot to keep it tidy and tangle‑free.

An optional storage pouch, slightly larger than a CD case, is also available, with a magnetic closure, made of a tough nylon at the rear and a neoprene material on the front, and an internal loop is included to store the optional USB‑A adaptor. All three elements of the SoundWire system look very well made and capable of surviving a long life on the road.

SoundWire Technicalities

The SoundWire delivers a nominal 0dBu balanced analogue output if presented with a full‑level 0dBFS digital source. This choice of audio level might seem a little odd, but it’s ideal for live‑sound applications since it works acceptably whether connected to a mic preamp (set with low gain and/or a pad) or a line input (with some added gain). It’s roughly the same as might be expected from a modern keyboard, for example.

On the test bench the review sample actually delivered +0.17dBu on both channels (matched within 0.01dB) for a 0dBFS output, and the frequency response measured flat within 0.2dB across the entire 20Hz to 20kHz audio bandwidth. I noticed a very slight tilt downwards from low frequencies to high frequencies (0.15dB), which is obviously inaudible, but I wondered if this was affected by the load impedance, as transformer outputs often are. The above figures were obtained with a high‑impedance (>20kΩ) destination, and switching to a very low, legacy 600Ω load impedance did change things. The maximum output level reduced to ‑1.7dBu, and the frequency response tilt changed to a gentle upwards slope, enhancing high frequencies slightly. These variations are entirely typical and are insignificant in practical terms — to all intents and purposes the SoundWire performs consistently regardless of the likely load impedances encountered in normal applications.

Running the AES17 Dynamic Range test, I achieved a figure of 110.5dB (A‑weighted). That’s slightly better than the published specifications but on the low side by modern standards, where 116dB or higher is fairly common in modern interfaces and converters. My rule of thumb is that anything better than 116dB is of professional mastering quality, and anything below 100dB is junk. But while the SoundWire is 6dB below mastering grade, it’s far from being poor (it’s still 6dB better than Behringer’s ADA8200, for example, with which many users are perfectly happy) and, without any doubt, it’s the best‑performing USB adaptor cable I’ve ever measured! The way I look at it, the SoundWire prioritises convenience and practicality slightly more than mastering sound quality, which is entirely reasonable, yet still manages to achieve a perfectly decent audio quality that’s ideally suited to live‑sound applications.

One minor oddity arose during my bench tests, but Sonnect identified it before I did: the review unit’s output signal polarity was inverted on both channels. I only do bench tests as I’m writing the review but had been using the SoundWire extensively before that; absolute signal polarity is notoriously hard to identify in normal auditioning with random audio sources. I’m told that this error affects only early production units and that there’s a simple fix via a firmware update, which should be available by the time you read this. Early adopters can update their SoundWires via the firmware update by contacting Sonnect directly, but really this foible is irrelevant in typical live‑sound applications, so will have been completely unnoticed by most early adopters (as it was by me). It’s also easily corrected by the desk channel’s polarity inversion button. Of course, later production units will be corrected during manufacturing.

At present, the drivers are generic and while the latency performance is fine for playback applications, the delay becomes noticeable if monitoring live‑played virtual instruments. However, it can be used with third‑party drivers like ASIO4ALL, and Sonnect tell me they’re developing dedicated drivers for both Mac and Windows which will make it better suited in scenarios where very low latencies are desirable.

It sounds very good — it’s great that the focus on practical convenience hasn’t sacrificed the audio quality.

Conclusion

The SoundWire’s simple form hides a lot of complex, bespoke technology that pushes up the price (on a par with budget bidirectional USB interfaces). But then it completely obviates the need for stereo DI or transformer‑isolation boxes, is fully class‑compliant for plug‑and‑play usability, removes all safety concerns about phantom‑power catastrophes, and provides transformer‑balanced output signals at a convenient level. And it sounds very good — it’s great that the focus on practical convenience hasn’t sacrificed the audio quality. All of which should make the SoundWire very attractive for anyone who regularly connects laptops and similar devices to a mixer. In fact, having used it on several occasions now, I’m very reluctant to go back to my adaptor cables, DI boxes, or traditional laptop interfaces.