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Aqua - Formula xHD Optologic - DAC

by Aqua

Thank you for visiting The Audio Tailor.

We’re Stuart, Gabby, Nathan and Vaughan. It’s a pleasure to have you here!

The first question we get from customers usually starts with, “What’s the difference between...”

When you’re shopping for new speakers, a turntable, or even thinking of putting together that home theatre of your teenage dreams - you’ll likely be faced with stacks of comparisons.

Why would I buy the Bluesound Pulse 2i when the Flex 2i is half the price?

Is Aqua the best?

Should I wait for a sale? Or get this now? What will I be missing out on when the new model comes out next year?

Endless questions. Lots of FOMO. Loads of hmm-ing and ha-ing.

And there SHOULD be.

Because you don’t go to a Hi-Fi store and drop $2000, $3000, or $15000 on something you're not 100%, positively, secure-in-your heart sure of.

It’s a lot of hard-earned money on the line.

Imagine doing hours of your own research. Reading up the suppliers’ websites, taking notes from Hi Fi blogs, categorizing the differing opinions as you trawl r/audiophile. You know what you’re getting. You’ve narrowed the online stores down to the final five. You’ve checked and re-checked that you’re getting the best deal. You’re sure you’re not getting ripped off by shipping.

You hit the “Checkout” button. Momentary relief!

That is...

Until your speakers haven’t arrived by the estimated delivery date and you have yet to hear a peep about its progress.

Until your new turntable arrives with a crack in the dust cover.

Until your long-awaited amp set-up fails to deliver the kind of sound you had in mind. Now you’re not even sure if you got the right one anymore, or how to troubleshoot it.

What could possibly be worse?

What about: No after-sales service. No phone number to call. And no one responding to your tickets.

Not to mention the hundreds of man hours you’ve already lost on reading layman opinions from the likes of Graham H. from Melbourne and Sarah D. from Perth; dutifully scrolling through pages and pages of reviews. Torturing yourself by looking for all the ones with less than 3 stars... when you could have been sitting back and diving into a whole new world of immersive sound and deliciously satisfying body vibrations.

Would it make sense to go to audio specialists that know brands, specs, and installation like the back of their hands?

Should you spend less time on weighing up pros and cons and more time enjoying good music?

Want to get the absolute best home theatre for your budget and surroundings without the weight of 100++ brand offerings bogging you down?

We like to think so!

And that’s why we’re here. Two things to know about us:

Thing 1: We were voted Australia’s 2021 Hi Fi Retailer of the Year (Yay! And THANK YOU!)

Thing 2: This is purely because we are sound specialists and audioheads - NOT salesmen.

We got into this business because we genuinely love audio and because we realized there was a lot of faceless dropshipping in the HiFi industry - and not enough expertise out there. People who keep coming back to us do so because they’re getting attention to detail and individualized solutions that they can’t find elsewhere.

Our clients don’t need to worry about budget, brand name, or size.

All they need to worry about, is talking to us.

Because, when you come to us, you’re in for a conversation.

We want to know the picture in your head.

That final portrait of you back from the flea market with Pearl Jam’s Ten, eager to place it gently upon a turntable you haven’t quite decided on yet.

A summer barbeque in your garden with the boys. Having a yarn around a beer-filled cooler while appreciating the crisp, clear, quality of sound streaming through the open doors of your listening space.

The kids having mates over - quiet for once - immersed in a good movie, lights out, in the comfort of the home theatre that is your pride and joy. “I wish we had one of these at our place!”

Once we know precisely what your ultimate scenario looks like, we’ll want to know what you’re working with.

What kind of budget have you set aside?

What’s the existing set-up look like?

How big is the listening room you have in mind?

How much ambient light is coming in?

Are you running drywall or wood panelling? Carpet or hardwood?

What about room resonance and reflection?

No idea what we’re going on about? No worries. We intend to talk you through all that. Our aim is that you get the absolute best sound system for your home, at a price point you’re happy with, and an aesthetic you can’t help but want to show off.

To get to this end goal, an unhealthy interest in all things audio simply isn’t enough. That’s why we spend countless hours behind the scenes sourcing products from only the most reliable brands and trustworthy suppliers - regardless of their branding and marketing.

We don’t rely on them to tell us what’s good about their equipment. We’ve developed our own proactive testing process to judge what’s what. So you get hands-on knowledge every single time. Coupled with our tight networks and stable supply chain meticulously refined over the years, we strive to ensure that the experience you get at The Audio Tailor is personal, seamless, and painless.

Personal, because it’s uniquely you in musicality, design, and taste. Your options are hand picked by us from amongst some of the world’s biggest, best, and most dependable brands.

Seamless, because we’re only small. You get one of us. Not one of dozens of salesmen milling about the place, working for commission and pushing the most expensive products.

Painless, because we don’t recommend anything until we’re clear about your needs. We follow up with you to make sure everything’s arrived in one piece. For us, the transaction isn’t over until your equipment is safely installed and fully satisfying.


Some of the big things we feel are missing in the HiFi world are:

  • The need for expertise before, during, and after the sale
  • A vast wealth of comparative knowledge, and
  • A commitment to end-to-end service.

At The Audio Tailor, we hope we’ve made it clear that service doesn’t shut off when a problem pops up. It’s an opportunity to tighten the ship we run, bolster our 5-star reputation, and most importantly - make someone’s day.

Hi! We see you’ve actually made it to the end of this page. Love it!

We’d like to end this by giving a shout out to all the enthusiasts and audiophiles we’ve been fortunate enough to work with over the years. It has been a privilege to share our desire, passion, and journey for the purest sound and finest entertainment solutions for your homes and businesses.

Thank you to all our customers - past, present, and future - for helping us chase after something above the ordinary.

To make your audio dreams come true - call, email, or hop on down to our Brisbane store.

We’re looking forward to meeting you!

Product Description

The new Formula xHD Rev. 2

The Optologic R2R conversion system

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.


Aqua's 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 electrolytic capacitors, all other caps are Tantalum, solid-polymer OS-CON and double-metalized MKP.

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).

The xHD update

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 native DSD512

xHD improvements:

  • 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 DSD512
  • 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)

Analog module Rev. 2

New level of sonic performance. The new boards implement new output transformers, specially selected super-fast active components and improved polarisation of circuitry.



    • Proprietary Optologic D/A conversion system. Pure R2R ladder - FPGA (Field Programmable Gate Arrays) based without digital filter
    • Galvanic and magnetic isolations between the FPGA and the four branches of the R2R ladder converter
    • Jitter free digital interface AQlink PRO (I2S protocol), uncompromising digital connection to La Diva cd transport
    • Discrete R2R ladder DACs with low noise precision resistors
    • Zero S/PDIF Jitter design, digital receiver stage PLL (phase locked loop) technology
    • High-performance AQ Discrete Regulator (MOSFET, J-FET, BJT) for analog and digital DAC’s power supply
    • 2 separate low noise C-Core power transformers, one for the analog and one for the digital section
    • MODULAR DESIGN with upgradeable multi board platform
    • Transformer-based true balanced audio output stage
    • Fully upgradeable high-speed USB hybrid 2-stage XMOS xCore XE216 + FPGA, Fully-floating (isolated) USB decoding and clock generation by FPGA with proprietary code
    • Proprietary USB Firmware / driver: Apple MAC OS - Linux OS : USB asynchronous native support, no need to install drivers software
    • Digital phase selector on front panel
    • High-quality parts selected for sound quality: Tantalum, solid-polymer OS-CON and double-metalised MJP capacitors, low noise Metal Foil ultra-precision resistors, double metallized film pulse capacitor, ultra-fast diodes, halogen free cables, Aluminium anti-resonant cabinet with Nextel
    • RC5 IR remote controller (optional)
    • Designed and handmade in Italy


    • Digital to analog conversion type - Proprietary Optologic D/A conversion system, Pure R2R ladder - FPGA (Field Programmable Gate Arrays) based without digital filter
    • Supported Native Sample Rates - AQlink / I2S serial bus - USB PC Audio : 44.1kHz to 768kHz PCM up to 24 bits. DSD64, Native DSD512. Supports DSD via DoP on all inputs
    • DAC architecture - Multibit sign magnitude R2R ladder (upgradable)
    • Asynchronous USB (High Speed) - USB Audio Class 2 with Type B connector
    • Digital Receiver - PLL (phase locked loop) technology 128 or 256 FS internally selectable
    • AQlink (I2S bus) - LVCMOS level
    • Oversampling factor - 1 x
    • Digital inputs:
    • RJ45 AQlink (I2S serial bus) - PCM 24 bit / 768kHz – DSD64, DSD256 via DoP
    • BNC coax (S/PDIF) 75 ohm - PCM 24 bit / 192kHz – DSD64 via DoP
    • RCA coax (S/PDIF) 75 ohm - PCM 24 bit / 192kHz – DSD64 via DoP
    • AES/EBU balanced 110 ohm - PCM 24 bit / 192kHz – DSD64 via DoP
    • USB port - PCM 24 bit / 768kHz – DSD64, DSD256, DSD512
    • Modular input:
    • AES/EBU balanced 110 Ohm - 24 bit / 192kHz - DSD64
    • RCA coax (S/PDIF) 75 Ohm - 24 bit / 192kHz - DSD64
    • AT&T (ST Fiber) - 24 bit / 192kHz - DSD64
    • Optical TOSLINK - 24 bit / 96kHz
    • Analogue Outputs - UNBAL 2 RCA Output 2.4 V RMS. BALANCED ( passive transformer's symmetrical ) 2 XLR Output : 3.8V RMS
    • Output Impedance - 10 ohm RCA - 600 ohm XLR
    • Load Impedance - 10 kohm (min.) RCA - 600 ohm XLR
    • Frequency Response - 20Hz to 22kHz +0.5dB/-0.5dB
    • Phase Response - Linear phase
    • THD + N - <0,016% 1KHz -10dB
    • Main processor - STM-ARM microcontroller
    • Controls - 9 Button on front panel, IR Remote, Isolated RS-232 D-SUB 9-pin connector
    • Front Panel - Power, phase invert, mute, input switch, RC5 remote sensor
    • Power Consumption - 100-115V / 220-240V; 50 or 60Hz - 58VA
    • Dimensions - ( W x D x H ) 450 x 370 x 100 mm
    • Weight - 9kgs
    • Front finish - Satin Alu Silver or Satin Black
    • Case finish - Grey Nextel powder coated

Please enquire for in-store stock levels

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