GC1

Reviewer: Srajan Ebaen
Financial interests: click here
Sources: Retina 5K 27" iMac (4GHz quad-core with Turbo boost, 32GB RAM, 3TB FusionDrive, OSX Yosemite. iTunes 14.4), PureMusic 3.02, Audirvana 3, Qobuz Hifi, Tidal Hifi, COS Engineering D1, Denafrips Terminator, Soundaware D300Ref as USB bridge/SD transport, Jay's Audio CDT2 MkII [on loan
Preamplifier: Nagra Classic, Wyred4Sound STP-SE Stage II, COS Engineering D1, Vinnie Rossi LIO (AVT module)
Power & integrated amplifiers: Pass Labs XA30.8; FirstWatt SIT1 monos, F5, F6, F7; Goldmund/Job 225; Wyred4Sound mINT; Nord Acoustics NC500 monos; LinnenberG Audio Liszt monos
Loudspeakers: Audio Physic Codex; Cube Audio Nenuphar; Kroma Audio Mimí; Albedo Audio Aptica; EnigmAcoustics Mythology 1; Boenicke Audio W5se; Zu Audio Druid V, VI & Submission; German Physiks HRS-120; Eversound Essence
Cables: Complete loom of Allnic Audio ZL 3000; Zu Event; KingRex uArt double-header USB cables; Tombo Trøn S/PDIF; van den Hul AES/EBU; AudioQuest Diamond glass-fibre Toslink; Black Cat Cable redlevel Lupo; Ocellia OCC Silver
Power delivery: Vibex Granada/Alhambra on all source components, Vibex One 11R on amps/sub
Equipment rack: Artesania Audio Exoteryc double-wide 3-tier with optional glass shelves, Exoteryc Krion and glass amp stands
Sundry accessories: Acoustic System resonators
Room: 4 x 6m with high gabled beam ceiling opening into 4 x 8m kitchen and 5 x 8m living room, hence no wall behind the listening chairs
Review component retail: €1'850, add €300 for a second ground cable

You can either be a cad, use CAD or own CAD. If you are, the Urban Dictionary calls you a rogue or bounder who is aware of the codes of conduct which separate a gentleman from a ruffian but finds himself unable to live up to them. If you use, those letters stand for computer-aided design. If you own, you're Scott Berry of Computer Audio Design, a definitive gentleman who, when it comes to noise on the ground line, is a major ruffian who definitely can't live with it.

Enter the GC1 Ground Control, his external box of bonded acrylic which internally is stacked with proprietary materials laminations that Scott gets made to his own specs. Those convert ultrasonic noise in the 700kHz-10GHz+ range into heat. Unlike others, this purely passive parallel box does categorically not connect itself to your AC power grid. It accumulates no 'charge' that would need to be 'drained'. But it does connect to your noise-critical gear with custom umbilicals of various terminations which grab only the ground pin/contact of a spare USB port on your computer or server; a free RCA, BNC or XLR socket on your DAC and/or preamp; or a ground post on a power distributor.

Voilà, HF energy which despite the best intentions of the engineers of your gear still propagates on its ground plane to interact with the music signal is siphoned off into the Ground Control which behaves like a virtual black hole. Whatever goes in doesn't come back out.

Scott is an electrical engineer who "did a fair amount of high-speed digital design in my previous jobs of R&D and manufacturing for Tektronix and Xerox". As he explains, in audio we deal with two voltage references, signal ground and earth which usually aren't connected directly but in some designs can be. "Signal ground needs to exhibit extremely low impedance. Even a slight increase can have detrimental effects on pace, rhythm and timing. Clearly this limits many common solutions to noise filters. From kitchen appliances like washing machines and microwave ovens to dimmer light switches, from cordless telephones, televisions and battery chargers to computers, routers and Wifi, each dumps noise into the mains power and mains earth.

"For safety reasons, any electrical device in a conductive casing must legally have an earth connection. Most audio components have metal housings that must be earthed to the same earth to which those noisy domestic devices connect. So most of our audio components are encased in a metal box that's actually conducting this very noise." It's why the CAD DAC, server and GC1/GC3 ground boxes use acrylic casings.

"In addition, audio products themselves create HF noise. The worst are servers, routers, WiFi and NAS devices and of course many people use laptops for hifi. Digital audio like DACs and CD players contain high-speed oscillators which produce significant HF noise. Legally there's only so much you can do to clean up the mains earth with standard filtering methods. The whole basis of mains earth is a low-impedance pathway for potentially dangerous electrical current. It's crucial that the impedance of the mains earth connection be as low as possible. Since typical techniques for cleaning up noise would raise that impedance, it limits how much cleaning can actually be done with AC filters without compromising legality and safety."

From this follows that you wouldn't want to simultaneously connect signal ground and safety earth via a Ground Control. "The Ground Control can connect to signal ground or mains earth. Some power strips have earth connections. Many audio components offer one to chassis/case or earth. Alternatively, if your power strip or component has a conductive metal case, you may loosen a screw and use a Ground Control cable with spade to connect to the case. But we generally don't recommend connecting both signal ground of a hifi component plus mains earth together using the same Ground Control. That would directly connect signal ground to earth to increase noise problems. In most higher-end audio gear, signal ground doesn't connect directly or at all to mains earth. In some DACs for example, there may be galvanic isolation which connecting earth to signal ground would override. I therefore recommend to connect our Ground Control to either signal ground or earth. Better still, if you have two Ground Controls, connect one to each."

"Having experimented widely suggests that the very best sonic result is achieved by connecting each audio component to one Ground Control. Obviously this has budget implications so we include two ground sockets on every GC1 [32x12x9cm DxWxH, 4.65kg] and six per GC3 [35x46x9cm,16kg] to accommodate multiple devices. It also enables one Ground Control to be daisy-chained to another, offering a way of adding HF noise reduction capacity without rendering the first Ground Control obsolete." Originally for a custom cost-no-issue commission, Scott even built a 'mega' Ground Control called GC-R [$21'500 with eight user-specified umbilicals] which weighs close to 50kg to support eight components. Chatting with Scott at Munich HighEnd 2019, he confirmed that increasing the volume/mass of his proprietary laminations enhances their effectiveness at capturing HF noise; and that his umbilicals are special ultra-low impedance cables customized for bandwidth far beyond the audio spectrum, not standard interconnects with odd connector pairings (the ends seating in the Ground Control are always bananas for a secure fuss-free connection whilst the 'send' ends are what the user orders).