Formula xHD


The Formula xHD Dac is the first in the aqua – acoustic quality’s production to show a proprietary D/A conversion system, that we name Optologic Dac. This conversion system follows the same multibit technology (already used in the previous world acclaimed dacs such as La Voce and La Scala) but with a discrete R2R resistors ladder instead of Burr Brown PCM1704 dacs. The xHD upgraded shows a diferent dimension in the digital reproduction.


 Introducing the new Formula xHD

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.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 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).

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, 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 internally selectable
AQlink (I2S bus)
LVCMOS level
Oversampling factor
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 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
<0,016% 1KHz -10dB
Main processor
STM-ARM microcontroller
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
( W x D x H ) 450 x 370 x 100 mm
9 kg
Front finish
Satin Alu Silver or Satin Black
Case finish
Grey Nextel powder coated

Formula xHD Brochure

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