Audio GD R-7HE MKII - Flagship R2R DAC

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(All devices are handmade to customer order)

Flagship R2R DAC

Built-in regenerative power supply, fully balanced, fully discrete R2R ladder DAC.

Highlights

• Fully discrete parts are used in a truly balanced power transmission design.
• 4 sets of fully discrete and independent DSD hardware decoders.
  
• 8 sets of fully discrete R-2R DA modules to form a two-channel symmetric push-pull decoder.
  
• 2 top quality Accusilicon TCXOs with frequencies of 90 and 98 MHz ensure synchronization of the entire device and are used for playback of all data rates without PLL upscaling.
  
• 32bit / 384K asynchronous Amanero USB interface synchronized with the FPGA. USB and HDMI modules are equipped with galvanic isolators and powered by two groups of independent isolated power supplies to avoid mutual electrical contamination between USB and HDMI.
  
• Using the latest discrete servo-stabilized power supplies, whose performance is comparable to that of batteries after more than a year of calibration and optimization for every part of the circuit.
  
• The digital circuitry uses these new discrete, servo-stabilized power supplies, while the clock and analog circuitry continue to be powered by pure Class A power supplies for the best sound, as determined by listening tests.
  
• The digital circuitry of the entire DAC consists of an FPGA and 7 CPLDs (both programmable devices), which allow to separate the different functional circuits and avoid interference.
  
• The FPGA operates in parallel data processing mode, even at the fastest data rate, and supports firmware upgrades to improve sound quality as new and better design ideas are found and implemented.
  
• The sampling rate of the input signal is displayed.
  
• Support 10MHz external clock input (default: 50 ohms, can be adjusted to 75 ohms).
  
• All digital mode settings can be changed directly on the front panel.
  
• There is a port for firmware upgrade on the back of the device (no need to open the cover to upgrade the firmware).
  

Features of the R-7HE MK2

It has been 4 years since the launch of the R-7HE in 2017. Thanks to the R-7HE's fully programmable circuitry, we've continuously updated the firmware to improve the owner's experience.

We will continue to update the current R-7HE even though we are now launching a new hardware design with the R-7HE MK2. The R-7HE MK2 was designed and tested in early 2020, followed by a year of continuous listening, software and hardware tuning. Productions and sales were not planned until we were completely satisfied with the realistic sound. The improvement compared to the previous generation is quite obvious.

1. By using the latest discrete, servo-stabilized power supply to power the digital circuitry, the noise level is comparable to that of a battery but without its dry and thin sonic characteristics, so the product's operating temperature is significantly lower than the previous model. The clock circuit and the analog circuit are still powered by a pure regulated Class A power supply to achieve the best sound results (New Upgrade)

2.Through listening and studying the sound of a turntable for a long time, we managed to integrate the characteristics of analog vinyl sound into this product, which is optionally possible via the front panel (New feature)

3. Both the USB and HDMI inputs are equipped with isolators and two sets of linear power supplies that separately power the USB and HDMI modules before the isolators to avoid interference from signal sources.

USB uses a two-way transmission isolator, which not only transmits the IIS signals to the FPGA processor, but also receives the synchronous clock signal sent by the FPGA processor. The USB interface itself is no longer equipped with clock generators. The synchronous clock is used to make the signal transmission more accurate and raise the sound quality to an excellent level. The sound quality is now actually better than the previous generation R-7HE, which was powered by the DI-20 (though not quite as good as the DI-20HE). The HDMI module is now equipped with an independent isolator to improve the sound quality of the HDMI input.

4. Display of the function for the sampling rate of the input signal.

5. The 10MHz clock input allows the use of an external clock.

6. The FPGA works in parallel data processing mode. The IIS signal is a serial data transmission. Each data bit requires one clock cycle. A frame of left and right channel data requires 64 clock cycles, so stability over 64 clock cycles is required.

Parallel mode only needs one clock to transfer and process the 32-bit data of the left and right channels, which greatly improves the processing speed and is less affected by the stability of the clock.
The IIS Input data (USB and HDMI-IIS) is reorganized into two parallel 32-bit data sets as it is input. After the SPDIF signal has been demodulated, it is also passed on to the next processing stage in two parallel 24-bit data sets. DSD data is also reorganized into two groups with 64-bit parallel processing as it is input.

According to listening comparisons, the parallel processing mode can make the sound clearer and more neutral, with better dynamics and a more analog flavor.

7. The clock management of the new architecture ensures a more stable clock, which leads to higher transparency and more details.

8. DSD uses the built-in asynchronous clock to improve timing, which significantly increases playback clarity and dynamics.

9. SPDIF supports DOP playback.

Fully analog regenerative power supply

A regenerative power supply is like a private generator built into the machine. It can largely filter out the noise on the power line, provide the audio components with super-pure power, and provide the audio system and end users with a consistent and impressive bass and high-analog signal.

In the implementation of regenerative power supply, the 120V/220V AC power is converted to DC power through the input regenerative transformer, which is then supplied to the regenerative waveform generator and driver through a parallel stabilized class A power supply.

A set of symmetrical regenerative waveform generators produces an extremely low-distortion 50Hz sine wave. After a balanced gain stage and a powerful driver stage, three regenerative output transformers output a pure voltage that is stable in both amplitude and frequency.

Two sets of parallel regulated Class A power supplies independently power the analog output stages of the left and right channels and the digital audio parts with their various processing functions. Both the regenerative waveform generator and the driver are powered by a stabilized Class A power supply, so that their work is not affected by mains fluctuations and disturbances.

The Class A shunt regulator has a very high input impedance to block interference and prevent noise on the power line from entering the audio circuit and affecting the sound quality; it also avoids crosstalk of the left and right signals by the power supply, improving separation. The low output impedance has excellent linearity and speed, which also allows for an excellent design for a regulated power supply.

Audio-GD's arguments for regenerative power supply design

1. Through the internal design analysis and actual test comparison of AP SYS-2722, the pure analog regenerative sine wave generator's distortion is much lower than that of digital synthesis generators.

2, The digital drive stage can have higher power conversion efficiency, but the all-analog drive stage has more analog sound.

3. The frequency of the regenerated waveform of 400Hz has higher power conversion efficiency. However, the regenerated waveform frequency of 50Hz is farther from the sensitive range of human hearing than 400Hz, and therefore the sound quality is smoother and more natural with 50Hz.

Specifications