Convertor Digital/Analog (DAC) Audio-GD D-27 2022 Edition

What's new in version 2022

Dual ES9038Pro DAC : The D-27 2022 Edition now features a pair of ESS ES9038Pro DAC chips, offering very low distortion and noise. Combined with discrete components, it combines the transparency and precision of these DAC chips with the musicality offered by transistors.

DI-20 Processor : The DI-20 processor in the D-27 2022 Edition corrects digital distortion, rejects jitter and provides the ES9038Pro DAC with a clean signal.

I2S and FPGA transmission : The USB transmits the I2S signal to the FPGA and receives a clock signal from it. The transmitted signal is more accurate and the sound quality is improved. To avoid electrical interruptions, the USB interface and the HDMI I2S input have built-in isolators.

Linear Fidelity Technology : Although the D-27 is an integrated, it nevertheless incorporates an excellent preamplifier and headphone amplifier. The Class A headphone amplifier is capable of delivering 2x16W of power at 25Ω or 2x10W at 40Ω. In addition, the integrated amplifier uses Linear Fidelity technology, ensuring a very low level of distortion over the entire frequency range.

D-27 2022 Edition key features

• 7 digital PCM filters and 4 DSD filters.
• The USB transmits the I2S signal to the FPGA and receives the clock signal for high precision transmission.
• The I2S and USB inputs have built-in isolators.
• DoP support from SPDIF inputs.
• Three separate low noise transformers for a total power of 130W. Digital circuit power supply is distributed by 15 high speed, low noise PSUs. Analog circuit power supply is distributed by 4 groups of regulated Class A PSUs.
• Two levels of gain: A gain of 12dB to accompany headphones with a sensitivity higher than 95dB and a gain of 22dB for headphones with a sensitivity of about 85dB.
• Relay controlled 4 channel volume control. Resistors operating in parallel for a tolerance of only 0.05%.

Dual ES9038Pro DAC

This High Fidelity DAC is equipped with two ESS ES9038Pro chips. These conversion chips are able to read high definition formats up to DSD512 at PCM 32bit 384kHz with an excellent signal to noise ratio (> 120dB).

This model is a 32bit 8 channel high performance system that is primarily found in studio and audiophile equipment such as SACD players, Blu-RAY, digital audio workstations...etc. This component is based on the ESS Hyperstream II architecture and offers considerable audio precision with a THD+N of -122dB and an active jitter reduction function.

In this type of configuration, each chip operates monophonically, which greatly improves performance in terms of channel balance while broadening and refining the soundstage. The dynamics are also enhanced.

Audio-GD also integrates Accusilicon high precision clocks. This allows a perfect synchronization of the data signals for a jitter reduced to its minimum.

Control by logic circuit (FGPA)

A FGPA logic circuit ensures perfect synchronization between the two decoding chips. Its role is essential: it separates the digital input stream in order to distribute the signal on each channel.

The FGPA also performs a reclocking function by applying a FIFO process to each input. The data is therefore processed in an environment where the clock signals are controlled with unprecedented precision, which naturally benefits the entire audio playback.

Finally, the logic circuit contributes to the diversity of compatible connectors and protocols since it manages the input and decoding of S/PDIF streams. The SPDIF decoding is therefore not operated by the ES9038PRO chips, but by the logic circuit which fulfills this same function with increased precision.

Perfectly balanced volume control

As far as volume control is concerned, the D-27 adopts a different scheme than traditional technologies. Indeed, in the case of a classic volume control, the device implements this function at the level of the input analog amplifier stage, via the reduction of the signal thanks to a potentiometer. As a result, the sound reproduction is directly impacted by the quality of the potentiometer used, which can result in a loss of detail or distortion. Even when using a high quality potentiometer, a loss of details can be noticed. Moreover, whatever the quality of the potentiometer, this system also impacts the Signal to Noise Ratio (SNR).

To overcome this weakness, Audio-GD has chosen to use an I/V Converter (Transimpedance Amplifier). Thus, the volume control results from a passive current to variable voltage conversion at the ACSS output amplifier, for which the output is the current signal and not the voltage signal. Therefore, the volume depends on the conversion of the current (I) to a voltage (V).

This design keeps the frequency range of the signal flat and therefore no details are lost. Therefore, there is no degradation of the sound quality, whatever the volume level. The brand also integrates just after this volume control a group of 4 diamond buffers without feedback in output stage, allowing to obtain a very low output impedance.

The quality of the volume control is particularly important in a balanced system. Indeed, it must guarantee the accuracy of the signal control on all four channels to obtain a perfect balance. Otherwise, distortion would be created, which could limit the interest of a balanced system. To maintain this balance, Audio-Gd also integrates a digital relay control on 4 channels allowing to modify the Vishay resistors and thus avoid unbalancing. This allows the D-27 to have an extremely efficient volume control for a high quality sound reproduction.

Finally, the volume control of the DAC can be varied over 100 steps allowing a wide control range of 90dB. Moreover, this control is exponential. Thus the volume progression is very smooth over the first 50 steps allowing a simple and precise adjustment, whether it is for use with headphones or high or low sensitivity speakers.

A discrete output stage

The last step for the signal is the analog output stage. This one must be particularly careful not to affect the overall performance of the DAC. This stage is located after the ES9038 and is based on discrete transistors only. The ACSS amplifiers as well as the gain process benefit from a non-feedback design and work with a current signal, allowing to limit greatly the conversions between current and voltage. The output buffers feature a pure Class A design with 4x150W on each channel, allowing the D27 to be used with the most demanding headphones without any problems. The exceptional design of this output stage allows for a very pure and neutral sound.

In addition, the D-27 integrates a very high quality USB interface: an Amanero Combo 384. Integrated in many Audio-GD realizations, this one has proven to be one of the best USB interface available. An excellent interface therefore, but which moreover is totally galvanically isolated, allowing it not to be subjected to potential interferences which could degrade the signal.

A massive remote control

The D27 comes with a beautiful CNC machined brushed aluminum remote control. A massive remote control that will prove to be robust and durable. It allows remote access to all the features of the device, including volume control, source selection and changing settings.