Castello Solo

Reviewer: Srajan Ebaen
Financial interests: click here
Main system: Sources: Retina 5K 27" iMac (i5, 256GB SSD, 40GB RAM, Sonoma 14), 4TB external SSD with Thunderbolt 3, Audirvana Studio, Qobuz Sublime, Singxer SU-6 USB bridge, LHY Audio SW-8 & SW-6 switch, Sonnet Pasithea, Cen.GRand DSDAC 1.0 Deluxe with POW, Laiv Audio Harmony; Active filter: Lifesaver Audio Gradient Box 2; Power amplifiers: Kinki Studio EX-B7 monos & Gold Note monos on subwoofer; Headamp: Enleum AMP-23R; Phones: Raal 1995 Immanis; Loudspeakers: Qualio IQ [on loan] Cables: Exact Express Flame, Furutech; Power delivery: Furutech GTO 2D NCF on source gear, Kinki/Vinshine Tai Hang on amps, Furutech DPS-4.1 between wall and conditioners; Equipment rack: Artesanía Audio Exoteryc double-wide 3-tier with optional glass shelves, Exoteryc amp stands; Sundry accessories: Acoustic System resonators, AudioQuest FogLifters; Room: 6 x 8m with open door behind listening seat; Room treatment: 2 x PSI Audio AVAA C214 active bass traps
2nd system: Source: FiiO R7 into Soundaware D300Ref SD transport to COS Engineering D1; Preamp/filter: Lifesaver Audio Gradient Box 2; Amplifier: Kinki Studio EX-M7; Loudspeakers: ModalAkustik MusikBoxx + Dynaudio S18 sub; Power delivery: Furutech GTO 2D NCF, Akiko Audio Corelli Corundum; Equipment rack: Hifistay Mythology Transform X-Frame [on extended loan]; Sundry accessories: Furutech cable lifts, Furutech NFC Clear Lines; Room: ~3.5 x 8m
2nd headfi system: DAC: Cen.Grand DSDAC 1.0 Deluxe with POW; Headamp: Cen.Grand Silver Fox; Headphones: Raal 1995 Magna, HifiMan Susvara
Desktop system: Source: HP Z2 work station Win11/64; USB bridge: Singxer SU-2; DAC/headamp: iFi iDSD Pro Signature; Speakers: DMAX P61 Headphones: Final D-8000, aune SR7000
Upstairs headfi system: FiiO R7; Headphones: Meze 109 Pro, Fiio FT3
2-channel video system: Source: Oppo BDP-105; All-in-One: Gold Note IS-1000 Deluxe; Loudspeakers: Zu Soul VI; Subwoofer: Zu Submission; Power delivery: Furutech eTP-8, Room: ~6x4m
Review component retail: €1'295

You're grounded. It's a teenager's purgatory. More is better. It might be—have been?—the American dream. Castello Solo. It bolts onto Akiko's Corelli Corundum. It's a virtual ground box on a short umbilical terminated to meet Corelli's mini XLR. The extra box acts as an extra drain for Corelli's ground chamber. It implies more makes merrier of Akiko's proprietary piezo-electric powdered compound over what's already in the Corelli's three chambers for the AC's three legs. It's all in pursuit of less is more where less equals noise, more means signal. Got that? Yes sir. Phew. But say you're not in the HiFi Special Forces. You didn't really get it. You're not sure about passive noise traps, virtual grounds and other tweaky esoterica. Be it Shunyata or Verictum, Acoustic Revive or Audio Magic, Furutech, DR Acoustics or Akiko, numerous brands have devised particle compounds which absorb radiated ultra-high frequencies and turn them into heat. Think more sophisticated pulverized ferrite beads. The underlying rationale? Our AC distribution wiring from wall to hifi kit plus interconnecting signal wiring are all prone to noise infiltration into WiFi's Gigahertz range. It has our cabling moonlight as garbage distribution network, our system ground as land fill. Passive traps are meant to siphon off some of that extraneous signal content not 50/60Hz AC or 20Hz-20kHz music signal. Over what bandwidth and at how many decibels of attenuation often isn't specified.

It's certainly not audible noise. We don't hear past ~20kHz. Out-of-band noise is simply believed to interact/interfere with processes like D/A conversion. That does concern the audible bandwidth. In this context my own Corelli Corundum purchased after its award-winning review hangs off my upstairs hifi's 8-outlet Vibex AC/DC filter. Nothing plugs into it. That makes it a parallel not series device. It represents a 'reservoir' below the power loom's impedance which captures radiated EM/RFI surrounding our AC arteries. That's the basic theory as I understand it. Castello Solo plugs into and scales up that reservoir. It's like the proverbial go-faster bolt-on mod. Nothing more needs doing. Nothing unplugs or rewires. Just jack Castello Solo into Corundum's mini XLR and that's all he wrote. The shortest review in history? By me? Not.

But one paragraph does constitute my full description of this black box atop another black box. The photo tells the rest. For more we need the father 'n' son team of Marc & Sander van Berlo who operate Akiko out of Maastricht in the Netherlands. Just then they were waiting on some parts to start formal first production. But Marc already had this: "While improving our Corelli power conditioner to the Corundum¹ version you reviewed and bought, I concluded that its ground chamber had the most impact on reducing background noise. Connecting our existing three-post Castello ground conditioner already had a positive effect but I did not fully like that now one connects the 115/230Hz power grid's ground not just to Castello but to the ground of two other devices plugged into it. Splitting those off immediately gave better results. This birthed the idea to support Corelli with its own full-fledged ground conditioner. This design is quite different since I wanted the new Solo to harmonize as much as possible with the ground chamber that's already inside Corelli."
________________________

¹ Corundum aka sapphire is a precious stone second in hardness only to diamond. It's commonly used as a spindle race in mechanical wrist watches where fast-moving parts would otherwise wear out. How many 'jewels' a watch has refers directly to the number of (often synthetic) sapphire parts it contains. A prime ingredient in the mineral mix of Corelli Corundum is sapphire. Acoustic Revive of Japan exploit tourmaline, quartz and Guiyang stone. Tourmaline emits negative ions which help neutralize static electricity and EMI. Quartz enhances this negative ion emission.

External ground boxes from CAD to Entreq, NordOst to Telos [12-post Telos Earth Grounding box at left], Ansuz to Acoustic Revive connect to each of our components via individual ground wires. Depending on box count and layout, this could create a very viperous star-ground nest. Never mind that no formal ground posts on much kit mean funky futz of miniature spades into chassis screws. Some external ground boxes run their own power cord. Telos add madly flashing LEDs. Castello Solo beheads the snake spawn. It runs a single short umbilical to Corelli Corundum. Lights out. There's not even one tiny idiot LED. It's the lazy guy's and gal's guide to groovy groundedness of which teenagers know naught. And it works in the dark. Out of sight, out of mind? Don't passive granular noise traps like Akiko's need regular discharging of their crystalline compounds to maintain top efficiency? If so, how to drain them?

Why virtual ground boxes have grown into their own audiophile category is perhaps at least partially visualized by circuit designs that shunt all noise to ground. That keeps their house neat whilst leaving all trash in the backyard like some properties did in our old Taos/New Mexico 'hood. Decrepit car carcasses. Discarded fridges. Kerb repeal. 'Keep thy ground pristine' seems a current counter trend based on feedback from advanced or simply adventurous audioholics. My own experience with the breed is spotty and smidgenly. A first date with CAD didn't want a second. A small four-deep Telos brigade definitely tickled my ears but to keep disqualified itself with non-stop blinking lights. I'm not exactly a virgin on getting externally grounded though clearly a stranger to the deep end of that pool. The simplicity of adding Castello Solo to my existing install now asked that I get fully wet; behind me ears. Rather than being solicited, I did the soliciting. Learning new stuff keeps this hobby and its horses on their toes. It can't just be speakers, amplifiers and DACs all of the time².
_______________________________

² This argument grows centipede legs once we own a carefully curated hifi whose key hardware is set in stone. Now the only things to still potentially polish are resonance control, grounding, EMI/RF traps and other finesse items which won't alter our overall tuning but potentially lower our system noise floor to let us hear more of—and from—what we already own. It's why people with already mature systems could be prime candidates for today's type product. Those still 'under construction' have more important things to do first.

"The standard and Solo Castello add noise attenuation to the ground. Many of our products have this ground-cleaning function which in my experience greatly benefits the sound. It was technically possible to support Corelli in this way without taking the power voltage outside the device. The mineral and crystal composition in the new Solo is quite different. I tried to match this mix to Corelli's ground unit. It's not the same formulation but harmonizes ideally. The Solo consists of one large compartment built up of different horizontal layers each connected with copper wiring which comes together at the banana plug in the back. There are more than 15 metres of wiring inside each Solo." In short—or long as it were—Solo's innards are rather more complex than a single chamber filled with powdered compound. As to whether Akiko's compounds can 'saturate' to require periodic 'discharge', Marc had this: "I can assure you that our tuning products do not weaken over the long term. In my home I still use the very first Corelli we made 10 years ago. It's still just as good and I even have the impression that it functions better now. The notion of charging up gemstones comes from the alternative health corner. Charging gemstones is said to be possible under running water or by exposing them to full-moon light. I'm much too down to earth for that. I don't believe for a second that gem stones millions of years old suddenly alter their physical properties with exposure to weak HF radiation as it occurs in our living environments. What I do believe and experience for myself is that as serious music listeners, we're extremely sensitive to this radiation. So I use all our tuning products continuously."

I wrote on that in a recent LessLoss review: "What the measurement crowd overlooks is that listening for pleasure involves people. That means multi-dimensional beings whose experiences happen on many levels. The physical is the lowest and grossest. Once we include psychology, mood, the mental, emotional and subtler strata meditators reach for, the richness of experience compounds. With it compounds what influences and shapes our experience. As we sensitize ourselves to our own deeper layers, we become more conscious of what affects them. Over time, listening to music playback can develop into such a sensitizing journey. We pay more attention. We notice and care more because more of us is triggered to participate beyond just the ears.

"In this subjective s(t)imulation, whatever improves our experience is good. Whatever diminishes it isn't useful. As far as our experience goes, naught else matters. Is it more important to feel good or to understand why? Should the latter be a prerequisite before we allow ourselves to feel good? Unless they're masochists, surely even diehard objectivists should say 'no' to making that a prior condition." So I see no reason not to benefit from devices I don't fully understand or at all if they improve my hifi experience which might well go beyond acoustic data perceived by my physical ears. A day after writing that, I saw this in a press release on Viborg Audio's Mariana power cable: "Ground noise stopper: tungsten mineral mix + graphene + electrolytic copper + aluminium." The italics are mine. For an alternate viewpoint, you could enjoy the manufacturer's reply [scroll to the bottom of this page] by Vladimir Kraz, an audio engineer with a degree from St. Petersburg who helms OnFilter and makes industrial powerline equipment.