Hardware Reviews

CAD drops the noise with USB II-R

CAD USB II-R cable review

Computer Audio Design USB II-R cable & USB Filter

The USB II-R is the latest USB cable from CAD or Computer Audio Design. CAD was one of the first companies that saw USB as the best solution for streaming high resolution audio, their 1543 DAC only had a USB input at a time when few DAC manufacturers had even got round to putting this connection on theirs. Now that USB has become the de facto connection for streaming audio and can carry far higher data rates than all but proprietary I2S connections, CAD founder Scott Berry looks like something of a prophet in the digital audio world.

I used CAD’s first USB cable as my main digital cable for many years, it was unusual for being relaxed and warm by contrast with the forward, even edgy sound of many alternatives at the time. Inevitably the rest of the cable world caught up so Scott has created a USB II version which has now been upgraded to the USB II-R cable that ups the game once more.

The USB II-R cable is distinguished by the presence of a separate 5V lead and a filter at the send end. CAD point out that the 5V is used for powering the receiver on some DACs, often just signalling to them that a connection has been made. Within the lighter casing are differential (balanced) conductors for the high speed positive and negative signal alongside a ground which provides a reference for both. The materials used in these conductors are not divulged but Scott points out that they have been arrived at through empirical research, essentially testing different options to find those that are best suited to the high frequency nature of digital signals.

CAD USB II-R and USB filter review

The filter on the USB II-R cable is housed in what feels like Delrin or similar engineering plastic. It contains a secret sauce network that claims to reduce high frequency noise on the signal, ground and 5V lines. Given that this type of noise is the reason why digital has a reputation for sounding cold and hard it makes sense to eliminate as much of it as possible. The CAD USB filter is available as a standalone device for use with other USB cables, it has a USB-B input and matching plug for connection to the DAC. So it’s at the opposite end to the filter on the USB II-R cable, which seems a bit odd so I asked Scott Berry what the thinking was.

“In our USB II-R cable, we are in control of the cable design and have been able to significantly reduce cable effects like airborne RF and intermodulation of signal and noise between conductors. Our standalone USB filter will be used with other manufacturer’s cables – where these issues will affect sound quality. So, that’s why I designed the filter to go at the B end, to help reduce these issues that many other USB cables have.

“The way I have configured the USB data lines and ground connection in the USB II-R cable does a really good job of reducing ‘antenna’ airborne RF from getting into the data lines. The independent +5V line is triple shielded for two reasons. It reduces noise from the +5 Vdc line from infecting the data lines and it also reduces airborne RF noise being picked up by the +5Vdc line.

CAD USB II-R and USB filter review

“I have done a lot of R&D with different shielding techniques and materials over the last 10 years and most have a negative effect on sound quality to my ears. I feel with the USB II-R Cable airborne RF noise is not an issue, but with many USB cables it can be.  From my research many USB cables also have +5Vdc noise on the data lines that has been picked up within the cable. Designing the CAD USB filter so that it connects directly to the DAC/streamer helps reduce these issues along with reducing a broad spectrum of unwanted noise from entering the DAC/streamer.”

Sound of USB II-R

I made a number of comparisons with reference cables and came to the conclusion that CAD USB II-R is one of the most natural and effortless digital connections available to the streaming enthusiast. It avoids the etched quality found in many but delivers a fully figured, rich and dynamic result that puts musical enjoyment ahead of maximum analysis. There is oodles of detail and it’s presented in a totally coherent, perfectly timed fashion regardless of the components in use. I tried it with an iFi Pro iDSD, Thrax Ares and various other DACs and amps with DACs built in and came up smiling every time thanks to the USB II-R’s ability to deliver music in such a way that it was highly detailed as well as being totally compelling.

You can get more open and airy sounding USB cables than this one but it’s hard to find the combination of precision and tonal richness that makes the presentation sound so right. On Steely Dan’s Babylon Sisters you get the glow of the polished production, the genius of the musicianship and the interplay between those musicians. The Purdie shuffle is very clear as is the effort that Fagen and Becker put into the arrangement. It’s rare to find a USB cable that times as well as the USB II-R which has an even handed tonal balance, they nearly always sound lean and lacking in body, emphasising the leading edges of notes but failing to fill out the harmonics behind them.

CAD USB Filter

The CAD USB Filter doesn’t make other USB cables sound like the USB II-R but it brings some of the qualities found with that cable to them. It proved beneficial even with very good cables, enhancing timing, focus and the sense of substance behind the notes mentioned above. On Babylon Sisters it also added dynamic impact which surprised me, it must be that the noise floor is pushed down so that there’s wider dynamic range, but whatever it does, it works. It loved the way that the snap of the snare and the vibrance of all the instruments was enhanced without upsetting the tonal balance. As with the USB II-R there is slight reduction in air and scale as well but the improvements make this a worthwhile compromise unless you are committed to room filling sound.

CAD USB II-R and USB filter review

With another well respected but ‘faster’ sounding USB cable the USB Filter brought depth to the picture by revealing the reverb in the recording, added scale to the image by essentially allowing more detail and less noise through, and most surprising also enhanced the sense of groove and involvement in the music. It clearly does a great job of stopping the noise and letting more of the signal get through to the DAC.

CAD USB II-R verdict

Scott Berry has produced a superb digital cable in the USB II-R, it delivers extremely high resolution yet has a fluency and musicality that is rare in any type of audio cable, maybe it’s time he turned his ear to the world of analogue interconnects. I don’t imagine he has the time or the inclination for that, the USB II-R took over a decade to develop after all. Anyone looking to get the most out of a streaming system would do well to try the CAD, it is undoubtedly in the top flight of USB cables on the market but by no means among the most expensive.


Type: USB digital streaming cable with filter
Conductor: not specified
Insulation: not specified
Shielding: none
Connector: fully shielded 24 ct. gold plated
Length: 1.2m
Cross section: 13 x 5mm
Warranty: 2 years

Price when tested:
USB Cable II-R £1,500/$1,500
USB Filter £750/$750
Manufacturer Details:

Computer Audio Design
T +44 203 397 0334



USB cable and USB filter


Jason Kennedy

Distributor Details:

Computer Audio Design LLC
T +1 541 728 3199

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