It ain't digital. Digital cables run analog voltages to represent binary values. The rise and fall of what ideally are square waves, for infinite bandwidth and slew rate, become markers in time for exactly when these values change. A physical analog is the CD. Its pits and lands represent the same values. Ideally the walls of the CD grooves are perfectly vertical. In practice, CD stamper and mould release conditions can render the physical markers more soft and vague than pristinely edgy. It's why special stamper protocols like XRCD can sound better even when the actual information encoded is the same as on ordinary pressings. Naturally the freeze frame which us technophobes just enjoyed—where a CD's pits and lands visualized the voltage states of digital cables—becomes blurry quickly. Just invoke reclockers, anti-jitter schemes and buffers. Their ilk would seem to render the entire issue mute. Engineers know and admit all of it. Yet if blessed with critical ears, they must also acknowledge that PCfi is far more finicky, about things that shouldn't matter, than we'd like. Embarking on this empirical path (that different USB cables sound different but he fancied none of them; why did they sound different; what design choices affected which performance aspects; how to optimize the lot for the sound he knew must be achievable) led to Rob Woodland's cable. That's its other meaning. It took keen curiosity on the subject to tackle it in the first place. Curiosity may have killed the cat but the Curious USB and its creator survived. If obituaries would have to be written, the buzz suggested it'd be about competitors. Finally, this branding suggests a safe haven for future cable types that shouldn't matter, like Ethernet. It's anchor bay also to boxes like the Qualia Physic S922 sdr, Uptone Regen, Schiit Wyrd [PCB at right] and Wyred4Sound Remedy. All of them impact the digital interface, albeit in ways not widely grasped yet. Which doesn't prevent their efficacy, only rational explanations. The real question is far more pragmatic. Will you lend an ear now and benefit; or insist on fence sitting until all these pesky mysteries are solved? Is your personal curious awake or a'snooze?


Rob's solicitation email said "please let me know what length of Curious USB you would like. Standard length is 0.8m but I'm happy to supply 1m or 1.2m." Given my aging eyes, hatred of WiFi and room layout, our music iMac sits close to the listening chairs where I can navigate iTunes by keyboard or infrared remote. The front-end electronics hunker farther down the sidewall in a Spanish rack to require a 3-metre USB leash. When I said so, Rob offered that "before handing the cable to another reviewer, let me work on a 3m length. The Curious is a complex cable to make by hand but I'll give it a go. If all works to plan, I can have it made within 2-3 days." Where there's a will, there's a widget. On some wiggle room between zero tech talk and an open invite to clone the Curious USB, Rob had this: "I've arranged the power leg in such a way that it doesn't dramatically affect the data lines; and to allow flexibility for the owner. The standard offering allows audiophiles to move the cable between systems or take the cable to a friend's place. In saying that, I can produce a dual-headed version or insert a connector in the 5V line for those who want to disconnect it.  It's a build-on-request scenario to suit a given setup. In a similar way, I also offer a variety of connectors including mini and micro usb to suit certain DACS. When it comes to USB, there really isn't a one size fits all formula. Regarding the tech, development was really a journey through all the materials that go together to make a USB cable. First port of call was the data lines - stranded or solid core?  Once that was settled, copper, silver or silver-plated copper? Then the diameter of the conductor. Then the metallurgy. And so on. Each step had an impact on the sound quality.
Left to right: The Bullet Plug which Rob manufactured under license from Eichmann; and his very own designs, the CablePod and Bayonet Plug.
"Once I settled on the conductors—high purity silver—it was on to the insulation materials. And so on. I then moved to the 5V power leg and onto the ground leg. Testing a huge range of conductors and materials, two interesting factors arose. 1/ shielding.  A lot of manufacturers go to extraordinary lengths to shield their data lines. In the main, this is done to prevent radiated noise from the 5V power leg and the ground leg from interfering with the data lines. Plus, we have EMI and RFI from the environment that may cause upset. However, all the shielding I tested produced an inferior sound. The cure was worse than the malady. How to solve this problem?  Instead of shielding the data lines, I decided to shield the 5V power leg (and remove it from the vicinity) and shield the ground. I then let the USB receiver chip do the rest. As you know, data via USB is carried as a differential signal. A mirror image of the signal travels down each data leg and is summed at the receiver chip, effectively removing noise. In this respect, the USB cable design is very similar to an analog balanced cable. 2/ the ground leg. The physical and electrical relationship between data lines and ground is extremely important. A lot of time went into this part of the design. Bottom line, the Curious was developed from the ground up based on listening tests at each step. The objective was to unlock the purity and dimensionality that digital files are capable of providing."