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True Balanced R2R DAC
- Fully discrete components are used in a truly balanced power transfer 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-class 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 verified in 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 works 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 live on the front panel.
- A firmware upgrade port is located on the back of the device (no need to open the cover to upgrade the firmware).
Features of the R-7 MK2
It has been 4 years since the launch of the R-7 in 2017. Thanks to the R-7's fully programmable circuitry, we've continuously updated the firmware to improve the owner's experience. We will continue to update the current R-7 even as we launch a new hardware design with the R-7 MK2.
The R-7 MK2 was developed 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. Using the latest discrete servo-stabilized power supply to power the digital circuits, the noise level is comparable to that of a battery but without its dry and thin sound 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 function)
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
a) 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 from the FPGA processor. The USB interface itself is no longer equipped with clocks.
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-7 powered by the DI-20 (although not quite as good as the DI-20HE).
b) the HDMI module is now equipped with an independent isolator to improve the sound quality of the HDMI input.
4. Input signal sampling rate display function.
5. The 10MHz clock input allows the use of an external clock.
6. The FPGA operates 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 transmit and process the 32-bit left and right channel data, 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 datasets as soon as they are 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.
The importance of FPGA/CPLDs
An important point about FPGAs/CPLDs is that they are programmable logic array devices. Today FPGAs are used in many high-end DAC products, such as the popular ROCKNA WAVEDREAM DAC.
We have used FPGA designs in DAC products since 2008. This machine consists of an FPGA and 7 CPLDs, which are the heart of the digital processing.
The hardware layout within the FPGA can be designed and arranged in software, allowing the hardware to be upgraded through software updates.
This has the advantage that this design offers a high degree of flexibility. It allows improving the sound quality, adding features and updating the product through software updates (firmware).
The tasks of the FPGA/CPLD
1. The FPGA implements a high-performance SPDIF demodulator (instead of low-power SPDIF demodulator chips such as DIR9001, WM8805, AK411X, etc...).
2. By combining clocking and FIFO technology for data output, it can be precisely synchronized with the clock and thus avoid jitter.
3. Built-in 2x, 4x and 8x digital filters and various NOS modes allow the user to choose the sound that best suits their personal taste.
4 Simulate the tonality of vinyl playback with a unique design.
Fully discrete output stage
The final stage in the signal path is the analog output stage, and the output stage has a crucial impact on the sound quality of the DAC.
No matter how excellent the digital circuitry, without an excellent analog output stage design, it will the sound quality is extremely ordinary.
The analog output stage is connected directly behind the DA 7 module, using only through-hole components (no SMD).
The high-speed ACSS amplifier is used for signal amplification and processing. The ACSS amplifier is designed without negative feedback and operates in current signal mode. It does not need to repeatedly convert the signal between current and voltage like other designs.
The output buffer stage is a pure class A single-ended FET design, and the two groups are connected in parallel to achieve lower output impedance. All in all, the output stage operates in a pure Class A condition without any negative feedback, so it can reproduce pure and lifelike sound signals.
The DAC has four built-in op-amps for DC servo function, so the DAC can work without coupling capacitors, which avoids noise and coloration. No switching elements are used in the entire signal channels following the DA module to achieve the truest and purest sound quality.
High performance power supply design
3 high-power R-core transformers with a total power of 150W and more than 40,000uF audio-grade filter capacitors ensure the purity of the power supply.
10 sets of newly developed discrete servo-stabilized power supplies and 7 sets of ultra-high-speed linear stabilized power supplies separately power the digital circuit of this product.
The self-contained, parallel-regulated, 5-group Class A power supply supplies power to the regenerative power driver and each part of the analog audio system separately.
All power supplies feature high speed and low noise.
structure
The DAC uses 5mm thick aluminum plates to separate the digital section, the left and right channel analog sections and the transformer section to avoid mutual interference.
Even the IEC socket in the power cord is housed in a copper shell and copper groove to avoid affecting the signal parts.
The analog parts of the left and right channels are symmetrically distributed on both sides of the digital part, with the same signal path length and distance, making the sound quality smoother and more accurate.
The DA 7 module is built between two aluminum plates to avoid interference from other circuits. The intricate arrangement and installation method were chosen to achieve clearer and purer sound quality and expand the sound field.
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