Aqua Formula xHD User manual

Formula xHD
D / A converter
Owner’s Manual
Rev 4.0

IMPORTANT SAFETY NOTICES
The triangle with the lightning flash symbol displayed on the unit advises the user of
dangerous uninsulated voltage inside the product’s enclosure.
To reduce the risk of electric shock, do not remove the cover.
The triangle with the exclamation point symbol on the component suggests that the owner
refer to important operating and maintenance instructions in the owner’s manual.
Modifications and alterations not approved by the manufacturer may violate adherence to
EC regulations and make the appliance no longer suitable for use. The manufacturer
declines all responsibility for damage caused to persons or property due to the misuse or
malfunction of device subject to unauthorized change.
In order to make changes that improve the already excellent quality of its products, aqua -
acoustic quality reserves the right to modify the information or the contents of this
manual at any time and without notice.
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Formula xHD Owner’s Manual

aqua - acoustic quality audio products are warranted to be free from manufacturing
defects for five (5) years from the original date of purchase. The warranty includes parts
and labour. In the event of a defect or malfunction, contact your dealer or aqua -
acoustic quality directly for return authorization. aqua - acoustic quality will remedy
the problem by repair or replacement, as we deem necessary, to restore the product to full
performance. Products must be returned using original packaging material only. Packing
material may be purchased from aqua - acoustic quality if necessary. This warranty is
considered void if the defect, malfunction or failure of the product or any component part
was caused by damage (not resulting from a defect or malfunction) or abuse while in the
possession of the customer. 5-year warranty is non-transferable in order to protect our
customers from illegitimate resellers. The warranty excludes the following components:
-Audio tubes
-NOS (New Old Stock) Components
CAUTION: Changes or modifications to this equipment not expressly approved by the
manufacturer could void the user’s authority to operate the equipment.
GENERAL SAFETY INFORMATION
The following general safety precautions must be observed during all phases of operation
of this equipment. Failure to comply with these precautions or with specific warnings
elsewhere in this manual violates safety standards of design, manufacture, and intended
use of the equipment. aqua - acoustic quality assumes no liability for the customer’s
failure to comply with these requirements.
• DO NOT operate the product in an explosive atmosphere or in the presence of
flammable gases or fumes. For continued protection against fire, replace the line fuse(s)
only with fuse(s) of the same voltage and current rating and type. DO NOT use repaired
fuses or short-circuited fuse holders.
• Keep away from live circuits. Operating personnel must not remove equipment covers or
shields. Procedures involving the removal of covers or shields are for use by service-
trained personnel only. Under certain conditions, dangerous voltages may exist even with
the equipment switched off. To avoid dangerous electric shock, DO NOT perform
procedures involving cover or shield removal unless you are qualified to do so.
• DO NOT operate damaged equipment. If the built-in safety protection features have been
impaired through physical damage, excessive moisture, or any other reason, REMOVE
POWER and do not use product until safe operation is verified by service-trained
personnel. If necessary, return the product to aqua - acoustic quality for service and
repair to ensure that the safety features are maintained.
• DO NOT service or adjust alone. Do not attempt any internal service or adjustment
unless a person capable of rendering first aid and resuscitation is present.
• DO NOT substitute parts or modify equipment. To avoid the occurrence of additional
hazards, do not install substitute parts or perform any unauthorized modification to the
product. Return the product to aqua - acoustic quality for service or repair to ensure that
the safety features are maintained.
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Formula xHD Owner’s Manual

In This Guide…
1 Operation and Features
2 Specifications
3 DAC Configuration
4 Front panel
5 Back panel
6 PC connection
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Formula xHD Owner’s Manual

1. Operation and Features
Make sure the supplied voltage is the one required by the device. Please ensure the
quality of the connecting cables, paying particular attention to the coaxial digital cable.
Often, numerous tests have revealed the importance of this cable for obtaining the best
sound quality. The transport unit which is responsible for the extraction of numeric data, is
affected by jitter, which is non-temporal coherence. In more recent years, this issue has
been taken seriously by some manufacturers, significantly improving the results in terms of
sound quality. aqua - acoustic quality counsels that this quality should be carefully
assessed in order to achieve the desired result.
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.
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. 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 free of all capacitors. The two output stages (one single-ended, one
transformer-coupled balanced) use discrete BJT and JFet with metal-film resistors. All the
electronics parts show an ultra low RF noise.
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Formula xHD Owner’s Manual

Modularity
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 optimization 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)
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 quad rate DSD (DSD256)
• Latest version of customized 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)
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Formula xHD Owner’s Manual

FEATURES
• 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-metalized 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
• 5-year warranty
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Formula xHD Owner’s Manual

2. Specifications
Digital to analog conversion type Proprietary Optologic DAC
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, DSD256
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 selectable
AQlink (I2S bus) LVCMOS level
Oversampling factor 1x
Analog Conversion method Pure R2R ladder - FPGA (Field Programmable Gate Arrays) based
digital decoding without digital filter
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 via DoP
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 ΩRCA - 600 ΩXLR
Load Impedance 10 k Ω(min.) RCA - 600 ΩXLR
Frequency Response 20Hz to 22kHz +0.5dB/-0.5dB
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 - 82VA
Dimensions ( W x D x H ) 450 x 380 x 100 mm
Weight 9 kg
Front finish Satin Alu Silver or Satin Black
Case finish Grey Nextel powder coated
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3. DAC Configuration

The Formula DAC is a modular equipment. More info at www.aquahifi.com.
4. Front panel
On the front panel, you find:
●power on/off switch
●mute
●phase invert
●switches for the selection of digital input
●LEDs for: power indicator, mute, phase invert, sample rate from 44.1 kHz to 384 kHz.
For other sample rate and DSD:
PCM 705.6 kHz (176.4 together 352.8 led)
PCM 768 kHz (192 together 384 led)
DSD64 (44.1 together 48 led)
DSD128 (88.2 together 96 led)
DSD256 (176.4 together 192 led)
5. Back panel
On the rear panel, you find:
●IEC connector of the power supply (220-240V or 100-120V).
●RS-232 D-SUB 9-pin connector
●Digital inputs :
- RJ45 AQlink (I2S serial bus)
- BNC coax (S/PDIF) 75 ohm
- RCA coax (S/PDIF) 75
- AES/EBU balanced 110 ohm
- USB port
Modular input:
- AES/EBU balanced 110 ohm
- RCA coax (S/PDIF) 75 ohm
- AT&T (ST Fiber)
- Optical TOSLINK
●analog outputs :
- RCA single-ended
- XLR balanced symmetrical
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Formula xHD Owner’s Manual
PIN ASSIGNMENT

The pin assignments of all of the XLR-type male analog outputs, the XLR-type
female digital inputs are as follows:
Pin 1: Signal ground
Pin 2: Signal + (non-inverting)
Pin 3: Signal - (inverting)
Connector ground lug: chassis free
6. PC connection
ADVICE: Windows users must install the driver prior to connecting the USB cable to
the PC (please refer to download section http://www.aquahifi.com/download.html ).
The USB cable that connects to a PC, must conform to the 2.0 specifications, and should
be of adequate quality. Please avoid using cable more than 2m, to avoid invalidating the
bus performance
True plug’n’play operation with Mac
Mac computers with OSX 10.6.4 and later have a native support for audio devices
compliant with USB Audio Class 2.0. This means that the driver is already included in the
operating system and the user needs not to install anything. Just connect the Formula
DAC to your Mac and it will be immediately recognized by the OS and ready to use. Macs
with older OS need update.
To use aqua USB as output device for your Mac, you need to select it as default output
device from the Audio Control Panel (Preferences -> Sound).
After selecting aqua USB, please check settings, you can select the sampling frequency
fixed for Formula DAC, regardless the native sampling frequency of all audio tracks.
For the best sonic results, you may want to use a player which follows the native
frequency of the tracks, like Sonic Studio Amarra or Channel D Pure Music.
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Formula xHD Owner’s Manual
True plug’n’play operation with Linux

PC with Linux 1.0.24 and later have a native support for audio devices compliant with USB
Audio Class 2.0 This means that the driver is already included in the operating system
and the user needs not to install anything. Just connect the Formula DAC to your PC with
Linux and it will be immediately recognized by the OS and ready to use.
Windows XP, VISTA, 7, 8, 10 O.S.
For the best sonic results, you may want to use a player which support ASIO*, like Foobar
or JRiver Media Center
*ASIO is a trademark of Steinberg Media Technologies GmbH
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Formula xHD Owner’s Manual

Handcrafted in Italy
aqua - acoustic quality
www.aquahifi.com
[email protected]