Hardware Reviews

CAD GC1.1: less noise, more music

CAD GC1.1 review

CAD GC1.1 Ground Control Box

The issues caused by high-frequency noise and addressed by the CAD GC1.1 are something that has been discussed in The Ear rather a lot in some of our recent reviews. Cambridge-based CAD was ahead of many in combatting the problem with the launch of the original GC1 way back in 2016. As many readers will appreciate, today’s environment contains significantly more high-frequency noise than a few decades ago — some of the main villains being wi-fi, routers, modems, computers and switch mode power supplies. Unfortunately, hi-fi components such as streamers, DACs and servers also contribute to the problem. Whilst such noise may be well outside the audio band, evidence suggests that it degrades the sounds we can hear. CAD’s founder/designer, Scott Berry, believes that dealing with the offending noise on the signal ground plane is critical to allowing sound systems to reach their performance potential. Unsurprisingly, CAD does not go into great detail as to exactly how its grounding products achieve their noise-reducing goals. The company does state that its products allow a simple and effective route for the noise to travel along, prior to converting it into heat. The technology involved is said to have been borrowed from aerospace engineering and features ultra-precise internal configuration and construction. With no further information from which to back up the claims, my only option was to listen. Without giving too much away, only a few bars of music were needed to convince me that GC1.1 was the real deal.

What exactly is the CAD GC1.1?

The CAD GC1.1 is surprisingly heavy and does not rattle when shaken. Being a sealed unit, I could not peek inside it to appease my curiosity regarding the inner voodoo without risking damage, so I remain curious. In simple terms, it is a black, rectangular box that’s as deep as many audio components with two input sockets to the rear. These connected to either your mains supply or up to two components in your system. Note the word ‘or’, meaning it would be undesirable to connect one input socket to the mains and another to a component, as this could lead to noise contamination between the two, which rather defeats the object of using such a device.

CAD GC1.1 review

I was also advised to avoid sharing a single GC1.1 between digital and analogue components. For example, having one ground cable from your DAC and, perhaps, another from your phono stage on the GC1.1’s second input would risk the high-frequency noise often found in digital devices, degrading the performance of the sensitive low-level analogue signal in the phono stage. With this in mind, I began by connecting ground cables from my DAC and digital server to the GC1.1 before experimenting by connecting the unit to my mains distribution block. The GC1.1 is priced at £1,995, but you must stump up a further £300 for each connecting cable. I confess to initially being taken aback upon learning the cost of the cable, especially considering that you might need two cables. However, sadly it is not a case of simply using off-the-shelf components to construct these cables, as the route from signal ground to Ground Control must be as electrically easy a path as possible to have the desired effect of draining high-frequency noise. The CAD ground cables cables are insulated in cotton and quite stiff, they can be supplied with XLR, phono, spade, USB, ethernet, BNC etc connectors. They can also be had with US, UK and EU power plug connectors by special order.

What does lower noise sound like?

I recently attended a demonstration of prototype noise-grounding products from a well-known cable manufacturer. There I experienced significant positive changes to the performance of the demo system, which were replicated in my home setup. Therefore, it was no surprise that the GC1.1 demonstrated easily identifiable improvements to the sound of my system. CAD’s Dave Denyer kindly brought over various CAD products to see which would be most suitable for me to review. As mentioned, we first connected the GC1.1 to spare plugs on my Melco server and Moon 780D DAC. We listened to a couple of tracks without the GC1.1 connected for acclimatisation. Playing the same track with the GC1.1 connected, we nodded as the music broke free of the speakers and gained a sense of dimensionality previously only hinted at.

Certain other products I have tried have done broadly similar things sonically but also introduced a slight brightness and thinning effect to the music. None of the CAD products we tried had this effect in my system; the music sounded softer and more natural, which was far more pleasant to my ears. There have been times when the bass in my system overwhelms the room at high volumes. Such issues were much reduced with the GC1.1 connected. Goldfrapp’s Ooh La La in DSD provided bass that was now more detailed and layered, the effect akin to what one might experience through superior speaker isolation.

CAD GC1.1 review

While initially struck by the improved imaging, layering and more natural presentation with the GC1.1 in situ, I soon felt a greater emotional connection to the music, which was particularly apparent in Nick Cave’s wonderful album No More Shall We Part. I’ve owned this CD since its release in 2001 and had previously considered it a little restrained sounding and lacking in definition. With the GC1.1 in tow, everything clicked into place. I played the CD rip through in full, transfixed by every aspect of the performance. I particularly enjoyed listening to the title track, which sounded wonderfully intimate. For fun, I streamed the Snoop Dogg track Drop It Like It’s Hot via Qobuz, which had a surprisingly deep, wide and spacious soundstage. Such qualities were far easier to appreciate with the CAD GC1.1 hooked up.

CAD GC1.1 on the mains power

Dave and I had discussed my trying a second GC1.1, which was to be connected to the mains distribution block that feeds my system. Unfortunately, a second unit was unavailable, so I had to disconnect the GC1.1 from the digital sources to see how it performed when connected to my mains distribution block. With the GC1.1 out of the circuit, the effect was akin to downgrading a source component. The music sounded comparatively shut-in around the speakers and was less interesting to listen to, I found I had to turn up the volume to engage with the music.

Next I listened to the same tracks with the CAD GC1.1 connected to my mains distribution block, and the smile returned to my face. Somewhat surprisingly, I felt the GC1.1 brought additional benefits to the sound of my system in this configuration, with few apparent detrimental effects. Now the music was a little more dynamic, and the lower frequencies possessed a little more depth to accompany the detail and separation I enjoyed with the GC 1.1 connected to my digital source components. The instruments were a little more defined and focused, and the soundstage was more solid. U2’s Exit from a CD rip of The Joshua Tree can often sound somewhat vague and indistinct, with the CAD GC1.1 connected to the mains supply, I had to re-evaluate Brian Eno and Daniel Lanois’ production.

CAD GC1.1 review

The classic track Missing from Everything But The Girl’s album Amplified Heart was now underpinned by a firmer bass line and the overdubbed vocals now leapt from the speakers in more compelling fashion. Perhaps the music sounded slightly dryer and less airy than via the previous configuration but overall, I felt the balance was preferable when the GC1.1 was connected to the mains distribution block. My appetite is now whetted to try a second GC1.1, or even a GC3.1, I suspect the combined effect could be something really special. ‘I Want More!’,  as my favourite German prog band, Can said, that also benefitted greatly from the CAD  GC1.1’s charms. The title track of Flow Motion proved even more fun. Both the timing of Jaki Liebezeit’s drumming and the dynamics and phrasing of Michael Karoli’s guitars were enhanced by the noise-killing properties of the GC1.1.

CAD GC1.1 conclusion

Before trying the CAD GC1.1, I had assumed my system to be well optimised by using a dedicated earth stake in the garden and quality mains cables and distribution block – clearly, I was mistaken. As I already mentioned, removing the GC1.1 from the circuit, having enjoyed its contribution over many hours, caused a significant downturn in performance. Spending £2,295, or indeed £2,595 if two cables are used, on a passive device may raise eyebrows amongst those without first-hand experience of CAD’s ground control range. However, I would rank the effect of the GC1.1 to be at least akin to the benefits of a piece of electronics of similar cost and often beyond. In today’s electrically noisy environment, I consider the CAD GC1.1 to be an essential audition for anyone with a half-decent system. A word of advice here, once you have heard how your system produces music without the detrimental effects caused by high-frequency noise, there may be no going back.


Type: Passive ground noise reduction system
Connections: 2x 4mm sockets
Size HxWxD: 89 x 105 x 320mm
Weight: 4.6kg
Warranty: 2 years

Price when tested:
Ground Control GC1.1: £1,995
Ground Cable: £300 each
Manufacturer Details:

Computer Audio Design Ltd
T +44 (0) 203 397 0334


noise reduction device


Chris Bailey

Distributor Details:

Computer Audio Design LLC
T +1 541 728 3199


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