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
