AQUA Formula xHD master-class Optologic DAC - R2R resistors ladder type

NZ$ 21,995.00 ea (incl. GST)

The Art of the Digital domain


The NEW FORMULA xHD features the following upgrades and modifications compared to the original Formula DAC:
-    New firmware release 3.0 for the main FPGA (DAC) with optimisation of the code
-    New USB board with hybrid architecture cod. A108

Upgrading original FORMULA to xHD
The update for the Formula units of existing owners consists of the following hardware / firmware modifications:
1. new hybrid USB Board cod. A108 (high-resolution up to 768kHz PCM and DSD256 (Quad DSD)
2. hardware modification of board P1108 connected to USB board
3. new firmware of main FPGA (R2R ladder DAC) with optimisation of the code
4. update of firmware of main micro controller STM32

Modularity our propriety Optologic DAC

The Optologoc R2R conversion sysrm
Aqua believes that the more musical D/A conversion system is based on the circuit usually identified as "resistor ladder".
This technology has been substituted in the mass-market by the so-called sigma-delta converters.
The sigma-delta converter is a near-completely digital circuit and for this reason it can be can be integrated on silicon and produced at low-cost. 
A quality resistor ladder DAC instead uses a circuit based on a set of high precision discrete resistors: at least 2 resistor banks, one for each stereo channel.
The Formula DAC is the first in the Aqua’s production to show a proprietary D/A conversion system, that we name Optologic.
The signals sent to the resistor ladders are generated by a proprietary digital circuit, implemented inside an FPGA (Field Programmable Gate Array).
Formula has a sign-magnitude converter structure, and this requires not two but four 24 bit resistors banks, each one made of very low tolerance discrete resistors.
In order to separate the digital section from the sensitive analog circuits,  galvanic and magnetic isolations are implemented between the FPGA and the four branches of the R2R ladder converter.
This creates complete isolation of all digital circuitry - including the clock - from the analogue section, for a clean, noiseless ground plane. It also plays the main role in the differential management of the R2R ladders, achieving perfect symmetry between the counter-phase halves. The result is the highest tonal contrast and naturalness.

Pure 1x native sample rate DAC 

The FORMULA, like the other Aqua models, is a digital filter-less DAC.
Our conviction is that in spite of the instrumental measurements showed by upsampling / oversampling DACs, they rarely are able to produce the same emotional and realistic results.


A third important aspect in the Aqua production is the modularity of the various electronic circuits.
Aqua equipment are not short life products: as modular, they are open to future improvements and to follow the evolution of the technology.
Formula is made of a set of circuits every one developed on a separate printed circuit board easily interchangeable.
As an example, each of the four resistors banks of the converter is separate and mounted on connectors.

State of the art digital and analog electronics

As explained before, the Formula DAC uses no digital filter or any other compensation, relying instead on maniacal attention to each sub-circuit.
The separate analog and digital power supplies are executed purely by extensive use of discrete BJT, Mosfet, J-Fet and ultra-fast diodes.
Passive parts were selected not just for the best sonic result but also for their top quality, longevity and reliability. With the exception of six superior quality electrolytics, all other caps are Tantalum, solid-polymer OS-CON and double-metalized MJP.
The signal path itself is direct-coupled and completely capacitor-free.
The two output stages (one single-ended, one transformer-coupled balanced) use discrete BJT and J-Fet with metal-film resistors. All the electronics parts show an ultra-low RF noise.
An advanced ARM microcontroller manages the user interface on the front panel, the IR remote command and the communication port (serial, RS232 standard).




• Proprietary hybrid 2-stage XMOS xCore XE216 + FPGA
• Fully-floating (isolated) USB decoding and clock generation by FPGA with proprietary code
• High quality, long life, low noise parts and modular design that distinguish aqua – acoustic quality equipment
• Sample rate in “Bit Perfect” up to 768 kHz PCM and quad rate DSD (DSD256)
• Latest version of customised XMOS X Core Driver on Windows OS (W7, W10)
• Native X Core Audio on Mac OS (Bit Perfect)
• USB Audio 2.0 operation on Linux (Bit Perfect)

This update has required significant optimisation of code for the main FPGA of R2R ladder DAC which has improved sound quality.

The new hybrid USB XMOS xCore 200 (dual core) + FPGA circuitry enables the high-resolution file playback up to 768kHz PCM and up to DSD256 (Quad DSD)


This formula was pliant, supple, fleet-footed and lissome. It's why it all fell into place at low volumes. Easy, relaxed, filigreed and intensely detailed were the key notes of this flavour.
Srajan Ebaen

You're not expected to eat it all. You survey it, then focus on what attracts you at that moment. Or, you allow it all to simply be there in its massively multi-paralleled simultaneity without reaching for anything. Again, think easeful, translucent, natural and superbly enunciated. The overriding note of other premium converters had been dynamic intensity and/or tonal saturation. It's from them that this presentation differed the most.

When a brief press release made the rounds that Aqua Hifi were about to bow their new flagship DAC during an April 9th 2016 dealer event in Belgium, it revealed nothing but the Formula name. Putting on my pointiest hat, I wondered. Had Aqua's established preference for R2R conversion finally clashed with native DSD demand? Did they mint a dual-engine machine that would auto-switch depending on signal format? Whilst some might call that pandering to fashion, others would call it smart business. Next a teaser photo emerged. It showed sample-rate indicators up to 384kHz but no DSD. Clearly Stefano Jelo & Cristian Anelli hadn't succumbed to DirectStream. Brava. 

That begged a question. What was optologic? Opto couplers aren't uncommon. They can isolate circuit stages and remove a ground connection. Toslink or glass fibre cables conduct electrical signal converted to light to accomplish something similar. Light-dependent resistors show up in attenuators from Tortuga Audio and Constellation Audio. Light-based tech also plays centre stage in Siltech's Saga electronics where "an incredibly powerful light source drives a photo-electric cell to generate DC for the amplifier output stage, galvanically isolating and fully decoupling the current gain stage from the AC supply". Light factors in infrared remotes and with optical drives from CD to DVD to BluRay.

On the face of it, none exactly explained an optological DAC. Aqua aqa Acoustic Quality weren't known for taking marketing liberties. Instead, our Italians had gained renown for fairly priced very well-done converters using mature no-nonsense tech with solid execution. The previous LaScala MkII flagship with tube outputs remains one of my reference machines. It went without saying. Had it just been summarily dethroned, the new formula had to be a winner. Prior to the full reveal, its ingredients simply remained mysterious. 

A week later, Cristian Anelli sent a prelim Italian tech PDF. He calling it a work in progress. This was confirmed by the text suddenly interrupting. Of what was there, Google translator made the following: "Galvanic and magnetic isolation are implemented between the FPGA and the four branches of the R2R ladder converter. This not only creates complete isolation of all digital circuitry including the clock from the analogue section for a pure clean ground plane. It also plays a vital role in the differential management of the R2R ladders, achieving perfect symmetry between the counter-phase halves. The result is high tonal contrast and naturalness not heard from digital machines. The Formula DAC uses no digital filter or any other compensation, relying instead on maniacal attention to each sub circuit. The analog and digital power supplies are executed purely discrete and with BJT, Mosfet, Jfet and ultra-fast diodes. Passive parts were selected not just for sonics but top quality, longevity and reliability. Except for six extreme-quality electrolytics, all other caps are Tantalum, solid-polymer OS-CON or double-metalized MJP. The signal path itself is direct-coupled and free of all capacitors. The dual output stages—one single-ended, one transformer-coupled balanced—use discrete BJT and JFet with metal-film resistors. All parts are characterised by very low RF noise..."

The astute reader took note of the 'super' symmetrical circuit. She probably suspected that the FPGA meant glue logic for non-audio R2R chips à la Metrum Acoustics. Actually, "there are no DAC chips, only R2R ladders executed with discrete precision resistors which are separated from the field-programmable gate array via optocouplers". With that, Aqua Hifi join the small band of merry R2R diskretniks like Aries Cerat, LampizatOr, LessLoss, MSB, Rockna Audio, S.A.Lab, TotalDAC and Wagner Audio who build their own ladder-type converters one resistor at a time. Unlike the former range topper LaScala MkII, the Formula has no tubes. That reiterates how Cristian Anelli isn't married to any given tech. He uses what works best for a given application. The breakdown of this formula was beginning to look most interesting. "Over our prototype R2R network without galvanic isolation, the 'optologic circuit' improved its performance. This became a one-step solution with dual benefits: perfect symmetry for the R2R network; and a true analog ground." 

For connectivity, the Formula's six toggle-selected inputs correspond to AES/EBU on I, BNC on II, coax on III, modular (AT&T ST fibre, I²S, AES/EBU, coax or BNC) on IV, USB on V and AQlink/I²S on VI. The 9 pin D-SUB for the RS232 interface serves home automation, PC remote and such. "Our main micro controller is an advanced ARM STM32." Now we get Optologic DAC. Given the unexpected twin benefits of optocouplers between digital input stage / housekeeping FPGA and where conversion to analog happens in balanced resistor ladder pairs, optical isolation was the next logical thing. To give credit where due, Cristian added that "it is a pleasure let you know that I designed the DAC's discrete FPGA conversion and STM32 micro controller in collaboration with engineer Gianfranco Meneghetti. He has more than 25 years of experience in the electronic industry working for various companies like ST Microelectronics, Ascom Safnat, Samsung Electronics Italia, Jabil Circuit and Teradyne. Gianfranco is great." A day after the Munich show, "I'm in the tunnel of the Optologic DAC upgrade project for the La Scala MkII." Cristian wouldn't rest on his laurels but shine more light—isolation by optocoupler—on his earlier models? "La Scala will have the same proprietary discrete R2R ladder architecture as Formula." How would Formula differentiate itself against La Scala MkIII? "The FPGA and logic parts will be the same but Formula gets costlier R2R resistors and a more sophisticated power supply for its DAC section. The LaScala will retain its hybrid tube/Mosfet circuit with the ECC81."

Here it's fair to be reminded. Unlike most DAC fabricators, Aqua are a more complete digital provider. They continue to support disc spinning with their dedicated La Diva transport. It's one of the potential I²S-over-CAT5 senders for their DACs' AQlink inputs. Below we see a short assembly line of transports at left; and at right Cristian's prototype white circuit boards of the Formula during a bug exorcism prior to the Munich HighEnd 2016 show.

Removing 12 hex bolts with additional plastic contacts to protect the cover's Nextel paint revealed unbelievably well-built innards executed with multi-stacked modules for non-obsolescence. Below we see the central housekeeping DSP board to the left, then three of the four discrete resistor ladder boards, with the vertical single-ended outboard module at the far right.

Personal beliefs. In my experience with well-done R2R converters of Aqua Hifi LaScala MkII, Metrum Hex/Pavane and Schiit Yggdrasil calibre as well as a few TotalDAC machines, they can share a very special quality. The kicker is that this needn't be apparent. If 'special' and 'hidden' would seem mutually exclusive, here's my pet theory behind it. Time-domain fidelity in upstream hardware gets obscured if the final transformers of electrical into mechanical energy—the loudspeakers—are "time confused". Be it steep crossovers or multi-driver integration issues, if the final link in the signal chain misbehaves in time, any gains (or really, avoidance of errors) made in that domain by preceding equipment won't translate fully or at all. A superior converter will still demonstrate its pedigree on any number of other fine hifi qualities. It just won't shine on the one which the speaker destroyed. I don't think it coincidence then that Holger Adler of Voxativ ended up with TotalDAC discrete R2R converters for their reference and trade show systems. Whatever potential weaknesses single-driver widebanders might suffer, filter-induced phase shift and multi-driver integration problems aren't amongst them. Following this train of thought, I picked the Zu Druid V widebander driven by the very simple FirstWatt SIT1 single-stage single-ended transistor monos for my first sessions. You may disagree with my belief but at least now you know what to disagree about.

To eliminate accusations of favouritism, my other chief DAC, Fore Audio's DAISy1, is a valve-hybrid Sabre-based ΔΣ affair. On matters of hifi, I really don't believe in the monotheistic absolute sound. Like a hindu, I happily worship at the altar of numerous deities. Like headfi vs. speaker fi, I can enjoy oversampling 5-bit converters and zero-sampling multi-bit competitors for their different flavours and perspectives. Where the Aqua Hifi decks are special and blossom that specialty into a load like the Druid V is with their quality of ease. Far from a weasel word like musicality, it can still seem far less concrete than soundstage scale or treble brilliance. That's because like physical tension in the body, you only notice it when your muscles relax; never before. This then is an observation about process not detail. It's not about things—tonal weightiness, separation, bass power, transient quickness—but how those things are perceived. If you don't know where to look, you won't see it. Once you do; and if your speakers are translucent to that quality; it's easy to recognise that flavour. Going back to a ΔΣ deck then shows you how that doesn't have it. It might have other qualities you prefer; or where it does more. It simply won't have the same temporal ease. Now it becomes a matter of how much you desire that quality; and how it rates relative to the many other possible virtues you find important, too. This acknowledges an essential. Like time coherence in loudspeakers, "easy digital" isn't the only or even primary criterion to matter. It's simply that if/when everything else that matters is perfectly handled or well enough, it could become the decisive difference because, somehow, listening to such a DAC has your ears and brain relax and more at ease.

This ease still differs from soft or insufficient drive. Some systems are tuned for adrenaline, excitement, spunk and jump factor. Others emphasise mellifluousness and chill factor. In visual terms, it's edge of seat versus deeply reclined in a plush lounger. For an unsympathetic listener, the first sound could be too intense and trying, the second too lazy, noncommittal and boring. In recent reviews of the Vinnie Rossi LIO DHT and S.A.Lab White Knight, I'd encountered components which played down energetic tension and muscle tone, then played up spacious fluffiness. Call it forward propulsion versus circular float. Today's ease isn't synonymous with float/flow. Ease of perception can coexist with a rhythmically charged propulsive system like the very PRaT-capable punchy Druid V. Here we hit upon limitations of established hifi language which fails to deal with these 'intangible' but very real aspects. Now using unfamiliar words or concepts risks sounding esoteric or obtuse. To avoid that reaction, it's far easier to throw out quick 'musical flow' or 'continuousness' verbiage, then hope that readers will associate the intended meaning. Fat chance.

For today's purposes, I merely repeat that this ease of perception related to properly done R2R conversion —as though your ear/brain were a muscle that's usually contracted and suddenly relaxes—doesn't disable musical tension or weaken pace and rhythm. Those are still things. Perception is the process which notices them. An easier process has a distinct feel or mode about it. One can learn to recognise and appreciate it; or perhaps is naturally sensitive to the absence of subliminal effort to refuse listening to anything else. Again, that's not me. I don't refuse to listen to premium Delta-Sigma DACs; nor do I consider them poor by any stretch. Heck, I own three of them. They just don't do this thing. Hearing a top R2R like the Formula is like slipping into a well-worn perfectly upkept shoe. It's supremely comfortable. This segues neatly into the Taoist proverb of Chuang Tzu - that "when the shoe fits, the foot is forgotten". 

Further on which, Cristian informed me that my loaner had the beta DSD firmware upgrade for DoP's 64/128DSD protocol. "For DSD, we can obtain the audio signal with a simple low-pass filter applied to DSD; or convert it to PCM followed by a DAC. We evaluated both options. From the design point of view, the low-pass is less demanding but in the end, we preferred conversion to PCM which takes advantage of the qualities of the R2R DAC; maintains our philosophy of no analog filtering at the audio output; and produced the best sonic results." In this, Cristian Anelli joins Bel Canto's John Stronczer who likewise prefers processing DSD as PCM. When a first comparison against our LaScala MkII didn't show an unequivocal lead on all fronts, I checked with Cristian on break-in and how many hours my loaner had. "Your unit has 4-6 hours on it. I think it needs 200." Given its parts density, that likely explained it. Shutting the main system down for 10 days of break-in simply was out of the question. So off into the guest room the virgin machine went for 24/7 2V coax signal from a Soundaware Esther M1 Pro. That was set to endless album repeat on an Android Belkin dock for never-ending charge. Without the connected integrated fired up, there was no noise pollution whilst the Formula stewed in its own juices. A week later, it was in proper fighting spirits back in the main system. Definitely don't judge it prematurely!

Core impressions. The first and most persistent one was extreme ease coupled to exquisite litheness. If their supple combination had a physical embodiment, it would have to be the winged messenger of the gods. The Greeks knew him as Hermes, the Romans called him Mercury. Walking into sound stages was spectacularly effortless. So was sensing their various moods or atmospheres. It felt not unlike gazing out the bay windows behind our speakers—at the greenery of the rolling coastal hills, the Atlantic ocean with Claire and Achill island in the distance—throughout our typical Irish weather which traverses four seasons in a day and turns on a dime. Except for a few cars and boats on the pier, grazing animals and seasonal wild flowers, the contents of this scenery never change. However, its mood changes; extremely and rapidly. Similarly to this general scenery outside, the space occupied by the virtual performers inside is more or less invariable. It's always behind the speakers bracketed by the side walls. Just like clouds, rain, wind, sun and fog affect the perception of our exterior landscape, the depth perception and exact lateral spread of the interior aural scenery change with recording. But essentially, we all know the standard dimensions of our private music stage. Our setup and layout determine it. With the Formula, the moods of this aural landscape—the feel, atmosphere and virtual weather conditions of the venues hosting the various performances—were unusually varied from recording to recording. Added to such tacit personality profiles of recorded space was their apparentness at low volumes. It took no array of powerful flood lights aka high playback SPL to sense it. Easy. Obvious. As such, a most natural entirely non-mechanical perception process.

In proper hifi terms, this spoke to very high contrast ratio, magnified resolution and top transparency. Because those values were very dialled up, their usual counterparts of weightiness and density were dialled down. That's back at the winged messenger's litheness and speed. It wasn't the thunder god Thor of the marauding vikings. It wasn't the expansionist Roman bringer of war, the god Mars. To invoke those macho characters would require emphasis on dynamics, transient bluster, welly and assorted violence. Not here. This formula was pliant, supple, fleet-footed and lissome. It's why it all fell into place at low volumes. Easy, relaxed, filigreed and intensely detailed were the key notes of this flavour. Pushy, forward, tense, massive, agitated, energetic and heavy were not. Whilst detail was in fact massive, it didn't launch itself forward like rubbernecking onlookers do at an accident scene. It was simply laid out like a lavish buffet.

You're not expected to eat it all. You survey it, then focus on what attracts you at that moment. Or, you allow it all to simply be there in its massively multi-paralleled simultaneity without reaching for anything. Again, think easeful, translucent, natural and superbly enunciated. The overriding note of other premium converters had been dynamic intensity and/or tonal saturation. It's from them that this presentation differed the most.

Like a secret guide, I was led to fare like the Take Bachexploits between pianists Güher & Süher Pekinel with the Jacques Loussier trio; to the Kirkelig Kulturversted's30 Years Fidelity compilation (Kari Bremnes' label); to Øystein Sevåg's Caravan CD and many more quality records of sophisticated music making... as though such unforced naturalness on part of the D/A converter didn't want to waste itself on coarser less intelligent more heavily processed stuff.

Such talk always risks the suggestion that anything else was less catered to. Any veteran listener simply trusts their instinct. Whatever selections a new component initially appears to be making on our behalf is just a reflection on its core virtues. Some gear first prompts us to get loud and gritty. Others has us pull out small-scale Jazz; or operatic arias; or low bass extravaganzas.

Unless any initial trend persists to indicate an imbalance or skewing which really does favours certain music styles or genres over others, all it really represents is our own nearly subconscious response to how it excels. Inspecting my collection of after-the-fact evidence for the first long session, a forensic hifi analyst would have profiled this report: lower than usual volume happiness due to visibility, intelligibility and articulation being exceptionally high; dominance of good productions without undue studio trickery to show off densely populated very capacious sound stages with a very dominant sense of venue; mostly acoustic not electrified fare; plenty of articulate percussive action, piano, strings, choral and acapella. Whilst the difference frisson of a new component was still most keen, the type music I gravitated towards in the first serious audition told its very own story, about what insertion of this deck brought to the table. With that mapped, how would it differ from or improve upon its LaScala MkII stablemate which combines BB1704K chips with a hybrid tube output stage?

to be continued………Srajan Ebaen

AQUA DAC for John Dako is the DAC I reach for when a ‘best’ first (digital) responder is called for.
John H Dako

Your own Personal Jesus? In the DAC world for yours truly, it’s Aqua Hifi’s La Scala MKII converter. The Burr-Brown PCM 1704 infused Italian sits proudly at the top of the Darko DAC Index, quite literally in a league of its own. The La Scala MKII is the DAC I reach for when a ‘best’ first (digital) responder is called for.

‘Best’ is a troublesome gift. One must accept its subjectively sighted foundations whilst being simultaneously mindful that no assessor can assess everything. Not food, not music and not D/A converters. The La Scala MKII is flagged as the ‘best D/A converter’ by these ears and this brain in the context of their collectively finite experiences. There might be a better D/A converter out there – it’s just that I’ve not heard it.

Returning our commentary to formal review territory and with proper professional posturing in tow, ‘best’ translates to ‘reference’.

Since being reviewed in March 2014, the Aqua statement piece – whose €4890 sticker presently converts to ~US$5500 – has successfully defended its RRP-segmented championship title against challenges from the Chord Hugo TT (US$4750) and the PS Audio DirectStream (US$6000).

In foregoing the nice-to-haves of headphone staging, a touchscreen, a digital pre-amplifier, a remote control and even DSD compatibility, Aqua DAC designer Cristian Anelli has poured his entire R&D/build budget into sound quality and sound quality alone. No bells, no whistles, just great-sounding D/A conversion.

The La Scala marries rock solid tonal density to enormous soundstaging for a presentation that connotes a strong but graceful handling of everything from the largesse of macro-dynamic shifts to the minutiae of textural finesse. Hanging up the reviewer cap again, it sounds Lovely with capital L.

And you’d think that’d be the end of it. But no. There’s more…

Ahead of introducing Aqua Hifi’s product line, which also features the more affordable but similarly non-oversampling La Voce S2 converter, to the US market by way of the T.H.E Newport Show 2015, Well Pleased AV’s Mark Sossa underscored these Italians’ un-stereotypical immunity to fashion:

“Aqua does not succumb to the whims of the latest market trends but instead carefully develops its products to withstand the test of time, designing and manufacturing audio equipment marked by the indispensable values of signal purity and acoustic fidelity pursued with the utmost dedication,” asserted Sossa via his press release.

When I caught up with Sossa again four months later at RMAF 2015, his enthusiasm for the La Scala MKII had been fuel injected by a change to another strand of Aqua’s adherence to well-established audio tech: tubes. The Aqua pairs 2 x ECC81 (12AT7) with MOSFETs for a negative feedback-free, Class A output stage. A reminder that a D/A converter’s audible performance resides with far more than just its DAC chip.

Moreover, tubes allow end users to tinker, to introduce alternative flavours via a process known as “rolling” – the audio world equivalent of changing a light bulb.

Sossa had done just that. He’d rolled the stock tubes – either JJ or Genalex according to Aqua’s sales manager Stefano Jelo – for a pair of NOS Telefunken.

And boy was Sossa excited about what he’d heard. So much so that he wanted yours truly to hear it for himself. And by Christmas I had the Telefunkens ready to roll.

The schedule intrusion of CES 2016 meant I’d have to wait until February to plug the NOS tubes into their Aqua sockets for the first time and then again wait out CanJam SoCal until I could be be confident that burn-in doubts had fully dissolved. That was late March. Listening proper then took place, on and off, A and B, throughout April.

These NOS (new old stock) tubes applied to this NOS (non-oversampling, filterless) decoder brought small but noticeable upticks in tonal colour saturation, soundstage depth and, most palpable of all, an even greater sense of ease – a defining characteristic (for this commentator) of digital done well.

The best was now even better.

Even with a recent price hike to €84 for a matched pair from Germany’s Tube Amp Doctor, the Telefunken ECC81 easily earn their status as an essential upgrade for any La Scala MKII owner. If you’ve the cash, don’t think twice – it’s alright.

But wait, there’s more…

March also brought limited and literal first word of a new flagship DAC from the radar-dodging Italians. That word was Formula. Retail pricing of €12,500 would more double down on its predecessor’s €4890. An April 9th launch event in Brussels came and went but little additional info spilled outwards to those not in attendance.

Only a single photo of the Formula graced (and still graces) the manufacturer’s website. At time of writing, supporting text and specifications sheet remain conspicuously absent.
Then came news that Aqua would show the Formula at Munich High-End 2016 and sales manager Stefano Jelo would be in attendance to handle any Q&A. The only proviso: no photos of the man himself. Jelo prefers the hardware to make its own introductions and then continue to speak for itself.

On the floor of the M.O.C. in May, Jelo’s Jean Reno-esque facial features and super snappy suit-up seemingly flew in the face of the man’s ‘no photo’ policy.

One might reason Jelo’s project: the tongue-twisting isolation feet maker ARIAMATERIA who also happened to showing in Munich. Whatever the reason, Jelo’s privacy is his own.

The ARIAMATERIA isolation feet are designed to be porous. Italian crushed stone ‘grit’, either brown porphyry or black basalt from the northern Italian region of Trentino-Alto Adige, is bound with resin and packed into cylindrical shapes of varying thickness before being top-and-tailed with 1mm thick neoprene pads to protect the supported equipment from scratches. All but the range starting AM10 feature an “monocomponent polymer” shock absorber.

That’s a proof-of-life diversion on Jelo’s other project. Back to Aqua. Back to the new flagship DAC. Back to basics – where tubes have gone bye-bye and where in-house built resistor ladders supplant the Burr Brown chips of the La Scala. Formula remains filterless with two R2R boards used per channel, one for each half of the waveform – four in total.

The Formula’s resistor ladder ‘branches’ deliver twice the sample-rate support of the outgoing (and long discontinued) PCM1704 chips whose dwindling supply points to one reason why these Milanese have gone with a bespoke multibit solution. The front panel sports eight LEDs indicating incoming PCM sample rates from 44.1kHz to 382kHz. They also make explicit Aqua’s ongoing red carding of DSD.

‘Round back, connectivity: AES/EBU XLR, S/PDIF RCA, S/PDIF BNC, AQlink (I2S) and USB. The protruding socket in the centre is modular for which the end user can specify AT&T ST Fiber, Toslink or a second AQlink(I2S), AES/EBU XLR, S/PDIF RCA or S/PDIF BNC.

Not only is one input modular. Potentially, so too are many of the Formula’s internal boards: the XMOS USB board, the I2S board, the FPGA board, the DAC boards and the analogue output boards (single-ended and balanced).

The following seven minute video was shot on the second morning of the Munich show. In the outdoor area caffeinated black stuff was being poured ahead of lunchtime’s bratwurst n’ beer takeover. Stefano Jelo walks us through the internals of the Formula. Note the twin potted C-core transformers, one each for analogue and digital sections, and the more sophisticated power supply board.

Only at interview’s end do we hear of another of Formula’s key features: Aqua’s OPTOLOGIC.

Just as a Toslink cable isolates its end points from electrical noise by carrying digital signals transferred to and from light, a similar opto-coupling method is used to join the FPGA board to the four R2R branches and then the R2R branches to the analogue output stage.

According to the manufacturer-supplied .pdf and translated from Italian to English using a combination of websites:

“The [dual function] OPTOLOGIC technique not only completely isolates all the digital processing circuitry (including clock ) from the analogue section in order to create a potential for a clean analog ground. The differential management of the conversion using R2R ladder branches allows for perfect symmetry between positive and negative. This gives the listener a heightened sense of tonal contrasts and naturalness.”

The same .pdf surrenders a little more info on the Formula’s output stage:

“The two analogue boards, one for the buffered single-ended output, the other for the balanced output, are made from fast, discrete components (BJT and JFET) and metal film resistors. No capacitor is present in the signal path. The balanced output is realised with transformers.”

At the end, a plot twist: Aqua intend to make their in-house resistor ladder tech available as a modular upgrade to the La Scala. That makes this story doubly interesting: a new product whose incoming tech will be trickled down to its predecessor, obviating the need for a completely new unit for existing La Scala owners.

Stefano Jelo says he intends to dispatch a Formula review unit down under to DAR HQ sometime in the next few weeks. I’ll be investigating what the big money can bring when one’s DAC spend extends beyond US$10K. Specifically, just how much better the Formula than the Telefunkened-up La Scala MKII? Questions that will be answered in due course.