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Audio-gd DAC-19: third Qobuzism for Audio-gd with this R2R DAC which opens the doors to sonic Nirvana!

Using a special type of analogue digital converter called the R2R, the DAC-19 from the Chinese brand Audio-gd provides a sound quality that surpasses what we heard elsewhere, even those stemming from the same brand. This ensures that Audio-gd are awarded with a Qobuzism for the third time!

By Barry Moore | Hi-Fi | October 7, 2015
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The Audio-gd DAC-19, which this year is celebrating its tenth anniversary, having undergone various changes, is the third devices from the Chinese brand that we have tested, and is also the third to be awarded our highest honour, a Qobuzism. We are not afraid to say that the sound results provided by these devices are of the highest level, and are the result of serious technical considerations on the part of the developers. They focus on the integrity of the transmission of their signals, and not on impressive quantitative results, and the benefits of this to the overall sound reproduction can be perplexingly good, and even a little mysterious.

Thus, Audio-gd positions itself against using reaction in the filters in its DAC, and uses a circuit they have developed, named the ACSS (Audio-gd Current Signal System). This is based on the principle of the ?current conveyor?, which transmits signals and provides, according to the manufacturer, a better performance that transports under the form of voltage.

We have seen the excellent audio results achieved with their DAC the NFB-2, and the NFB-15, the brand?s DAC and headphone amplifier, which gave perhaps the best sonic results that our ears have ever witnessed.

An important point, the DAC-19, using the digital to analogue chip of R2R conversion type, has been virtually entirely supplanted. This is due to cost reasons, due to their difficult production of chips using the Sigma-Delta principle, which transforms the data bits in a high frequency one-bit stream, called PDM (Pulse Density Modulation). This requires only a simple filtering to reconstruct the analogue signals.


Presentation

A solid box in black anodized aluminium and a natural, solid aluminium selection knob connects to the digital source in the centre of the box for the Audio 19-gd DAC. There are two buttons at the end of the façade, one for the power, and the other to invert the phase of the output signal.


On the back side, output audio signals come in on RCA sockets for standard use, as well as streaming on a mini XLR, which takes in three inputs, and can be connected to an Audio-gd camera accepting ACSS signals. In the middle, just above the base area, the digital inputs are found. There is a USB B to connect to a computer, and two S/PDIF optical and coaxials. The latter is doubled by an entrance to the professional AES/ABU BNC connector, but you can only connect to one of the two.


Production

There is no wasted space inside the DAC-19, where a beautiful transformer of R-core power type is found, the ultimate in this category, according to experts. The production is clean, and it is handcrafted by experienced technicians.


No less than eight stabilized linear power supplies power different sections of the DAC-19. From the recovery, there are four electrochemical capacitors, the Nover Audio Grade 3300 UF/63V that filters the resulting tensions, and ten capacitors of 1500 uF/35V, which were all of the Nover origin. The filter assembly tensions are stabilized by Zener diodes (regulatory voltage diodes) and transistors, which are mounted on chillers.


The digital filter is the same as that used in the DAC Master 7 from the brand, and uses an Altera Cyclone II circuit, a network of programmable logic gates (or FPGA ? Field-programmable gate arrays), which is used by Audio-gd as a digital signal processor to perform various digital filterings of the digital signals, as well as double-sampling, and quadruple and octuple samplings. It also generates and randomly distributes the quantization noise. You can see on the left of this FPGA that there is a bar for the configuration of the ?hardware? mode.


One can also see the receiving circuits of S/PDIF type, a DIR9001 (24-Bits at 96 kHz), manufactured by Burr-Brown, and also a 74HCU04 circuit for the signals of the fitness from the optical input, and two 74HC125 circuits, a tri-state line drive (the logic states 1 and O are of high impedance state corresponding to an open switch), used for switching sources, and are controlled by the input selector (the DAC-29 does not use a micro controller).

A USB board from the Italian manufacturer Amanero is compatible with digital signals of up to 32-Bit by 384 kHz, and also a DSD, but will also be limited by the 32-Bit/192 kHz, due to the use of conversion from chips that do not go beyond this quantization size.


Each DAC-19 channel uses a digital to analogue converter of the PCM1704K type, manufactured by Burr-Brown, and supported by 24-Bit/192 kHZ, which has only one channel and can reverse the phase of the signals, of optional use by Audio-gd. The PCM1704K, which outputs a current signal, makes use of the conversion type called R2R for using bits of the digital signals directly, in order to reconstruct the analogue signals by acting on a network consisting only of resistors. These have both a given value (R) and a double value (2R), without passing through a sampling phase.


The analogue signals are of output type of PCM1704K, the current form, and are then converted into voltage and filtered by a circuit using the ACSS technology (Audio-gd Current Signal System) from the manufacturer, using on discrete components, and not making use of any reaction in order to preserve the musicality. No capacitor is on the path of the signal to prevent staining and preserve its purity, and buffer field effect transistors are placed before pin jacks that are lower than the impedance output.

Listening

We were eager to discover the sound results provided by the Audio-gd DAC-19 using R2R technology. The NFB-2 and NFB-15 models from the brand had impressed using Delta-Sigma technology, which is the most common now, and we have been strongly impressed, to the point where we ask whether these devices would not be the best we?ve ever had in terms of DAC (and we have seen more than a few!).

From all evidence, the sound quality provided by the Audio-gd DAC-19 is of the highest class. We started our listening with the album Vespri per l'Assunzione di Maria Vergine by Vivaldi as directed by Rinaldo Alessandrini at the head of the Concerto Italiano, and we were plunged into a musical bath of extreme beauty, where all the instrumental lines enjoyed a remarkable finesse, an incredibly trimming of instruments, as they say, with an extremely vivacious attack on the ropes, and, without that restitution, the least of density in spreading its emotional message.

And yet, the small amplifier the Sony UDA-1 that we used is not really one to warm the sound message a great deal (and that is why we like to use it: for its neutrality).

And we rediscovered the vocal and choral passages of this work, which proved even more beautiful, showing a striking presence by deploying wide and airy soundscapes.

But, there, we left it on the default configuration of the DSP-1; that is to say, without riders, which have an 8x re-sampling of digital signals, an attenuation of -130 DB, a use of the PLL with built-in DSP, and Dither in the service.


So, we set up the DAC-19 so that digital signals are no longer processed by the DSP-1, and, for that, we implemented the jumper 1 to select the bypass mode. The digital signals will be sent to conversion chips natively in the most direct manner, and without oversampling.

And, what about the refund?

Well, if the basic restitution proved to possess a high level configuration, it reminded us a great deal of the NFB DAC-2, if we can trust our musical memory.

With the jumper in a position to bypass the DSP-1, the sound reproduction is simply stunning, and it's mostly the gain in terms of ventilation that brings in an increased sublimating of the original restitution. The sound expression was great.

It?s decided, then, that Qobuz will take the DAC-19 home for a little break before returning it to Audiophonics? but, in the meantime, we will hear Dangerous from the album Listen by David Guetta. And, again, the restitution was incredibly fine, everything was clear, clean, airy; the various melodic lines were perfectly detached from each other, without the cohesion of the restitution being affected in the least. Great stuff.

To conclude, we will not go so far as to say that the Audio-gd DAC-19 is the best DAC in the world, failing to have listened to all of them, but it is by far the best that has thus far passed into our hands. An absolute must for true music lovers in search of sonic truth!

Specifications
User's Manual, online help
Site Audio-gd
Contact (Contact Audiophonics, importer)

Driver: download the joint piece setup_2.exe.zip

Further Reading


Our thanks go to Audiophonics for the use of the DAC-19.

***

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