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R-28 NOS


Fully Balance Discrete Transistors Headamp And Preampamps All In One

8 group fully discrete R-2R DA converters (4 pcs DA-8 board) implementing balanced mode.

4 fully discrete native DSD decoders work in balanced mode .

32bit / PCM384K /DSD512 asynchronous transfer using the Amanero 384 usb input.

All inputs with galavanic isolator

Fully discrete current signal transmission design without OPA in signal path.

Built in real balanced headphone amp max output power achieve 9500 mW that can drive most headphone easy.

Support firmware update to improve on sound quality.

All digital process mode settings accessible by buttons on front  (No need  to open the chassis)


Please note: The product improve cause the inside or outside change without inform .
Summarize Use Manual Specs Custom Option Shipping Cost

Price:   USD1150 ( Exclude shipping cost)
The free mini remote controller not in warranty
Purchase the metal remote controller simultaneous price is USD40.

Please send your address, name  to audio-gd@vip.163.com  get the quote.

Click to download the driver of  Amanero combo 384

What's new in R-28 NOS:
       Some people love the sound of the pure NOS mode , so we design the R-28 NOS that optimize the pure NOS mode , offer the pure musical sound .
       The NOS design don't need the main clock signal for working, that is the advantage of the NOS design to avoid the effect by the main clock's jitter .
       In the R-28 NOS digital processor , we apply the zero delay technology that  guarantee the data and clock exact synchronization for much reduce the jitter .
       In the R-28 NOS design , we apply the galavanic  isolator before the DA parts and analog parts , isolate the all digital inputs and the digital processor , that offer the better clean sound quality .

Choice between R-28 2022 and R-28NOS:
       The R-28 2022 has built in Oversampling mode and NOS mode, that can flexile choice the different to choice different sound flavor for user.
      The R-28 NOS only built in the optimize  NOS mode , that more suite who like the NOS sound warm and smooth but still transparency and tubelike sound .

Some things you may need to know about the NOS design before purchasing:?
1AMany facts not commonly known about the NOS design :
        In the 1970'S, the first generation of CDP were released , and they used an NOS design .
        "NOS" stands for "Non Oversampling". Using a NOS design, specs are ordinary because the limited signal bit depth affects THD and S/N.
        Despite the fact that quantization noise affects S/N, the R-28 NOS still achieves very low noise levels, much better than most tube amplifiers and turntables, and much like a modern OS DAC .
        To get better specs on paper, many designs apply a quite complex LC analog filter after the D/A conversion. But the LC filter usually does not have a flat response and the large phase shift it causes also affects sound quality considerably.
        In 1980's, oversampling and FIR filter were invented, and allowed improving sound quality compared to applying an LC filter. Good specs were obtained on paper, so this technology has been largely applied ever since.
        But some people still liked the sound of the NOS design better and felt that without the extra processing, it did a better job at preserving the original character of the sound, like in real world, trusting their ears rather than specs.
        Therefore if you want good specs, the NOS design definitely is not for you.

2ADiscrete servo stabilized power supply:
Using the latest designed discrete servo stabilized power supply to feed the digital circuits, the noise level is comparable to that of a battery, but without the dry and thin sound characteristics of it, and thus the product's operating temperature is significantly lower than that of the previous model. The analog circuit are still powered by a pure class-A regulated power supply for the best sound results.

3ATube-like sound:

        The basic NOS design has a tube-like sound or a vinyl feeling . It may have to do with distortion being similar to these, typically between 0.01% and 0.1%. Some expensive USA-made DAC has even inferior specs but a lot people consider it has a beautiful sound .

       The R-28 NOS distortion is similar to a vacuum amplifier or turntable and to the expensive USA- made DAC referred upon. But the noise level is better than 120DB that much higher than the vacuum amplifier and turntable.

R2R-28 NOS feature:

1. 8 group built-in 24bit R-2R decoders and 4 native DSD decoders work with balanced mode.
2. All inputs and digital processor with galavanic isolators.
3. Two high-quality R-core transformers power supply.
4. 9-group of power supplies overall for the different components. The R-2R modules apply 2 groups of servo-controlled discrete PSUs .  The analog output stages are powered by the 2 groups of pure class-A PSUs. . The control module and volume boards use a separate PSU to avoid any contamination to the digital and analog signal components.
The unit has two gain modes, the 12DB on low gain for drive the headphone which has over 95DB sensitivity, and 22DB on high gain cooperate with the strong power ability,  enough to drive the HE6 which has around 85DB sensitivity headphones. If customer want to boost 6-12DB gain, in total 28-34DB gain.

6, Relay volume control boards built-in for accurate channel balance and transparent sound . 0.1% resistors are used in parallel to increase the effective tolerance to 0.05%.

Pros and cons of R-2R DAC  :
         1.R-2R will not convert the clock signal into the output signal.
         2. R-2R is not sensitive to jitter .Delta-Sigma D/A is much more sensitive to jitter.
         3. The output signal is much more precise compared to Delta-Sigma D/A .
        1.THD today is extremely good with Sigma Delta chips in comparison to R2R ladders are good too but not as good.
        2. Glitches and accuracy of the ladder resistors are very difficult to avoid and require complex technology to resolve it.

R-2R basic design in the market:
 The R-2R DAC is very popular nowadays and available from DIY kits up to  completely   high-end products. 
          In the low range DIY market, the R-2R design is often based on old technology designed a long time ago by MSB and only includes basic R2R ladder design and do not include the wonderful correction design of the original MSB technology. This design uses data shift registers logic chips in series mode to convert the data to an analog signal. The structural R2R technology issues cannot be avoided, and performance is solely depending on the accuracy of the ladder resistors. 

In the High-End market the R2R design is much more complex and achieves better performance. A basic R2R ladder is simply not sufficient enough to achieve good performance and high sound quality! Some manufacturers are using shift registers design. A less complex and less efficient design based on traditional logic chips working in serial mode to correct the ladder.
         A far better design switches resistors in parallel mode. An ultra-fast FPGA controls and corrects the R2R ladder. The parallel design mode controls every bit respectively and therefore achieve unprecedented performance. (In parallel mode only 1 clock cycle is needed to output all data; serial design mode needs at minimum 8 up to 24 clock cycles) The parallel design is much more complicated. Once designed properly it can correct every bit of the ladder.  Photo below shows a design with such FPGA,  can correct the unavoidable imperfections of the R2R ladder caused by intolerance of resistors glitches and achieve  best performance.


Accuracy of the ladder resistors (tolerance):
  Many people believe the tolerance of the resistors in the ladder is most important to reach best performance. Nowadays 24 bit resolution is standard. What tolerance is needed to achieve 24 bit resolution?
            When we look at 16 bit the tolerance of 1/66536, 0.1% (1/1000) is far not enough, even a tolerance of 0.01% (1/10000), the best tolerance available in the world today, still cannot handle 16 bit correctly; we are not even calculating 24 bit here!
           The tolerance of the resistor will never solve Imperfections of a ladder. This would require resistors with a tolerance of 0.00001% and ability to  handle 24 bit resolution. This is only in theory because the discreteness of the switch logic chips have already too much internal impedance and will destroy the impossible tolerance of a the resistor.
            The solution is to correct the ladder and not to depend on the tolerance of resistors. Its a combination of both: Ultra-low tolerance resistors controlled by a correction technology and very high speed FPGA which is applied  in in our design.


Importunacy of the FPGA/CPLD:
 FPGA/CPLD stands for Programmable Array Logic. 
            Nowadays the FPGA/CPLD is applied in a lot high end grade DACs; like the popular ROCKNA WAVEDREAM DAC. 
            We have applied the FPGA/CPLD in our DAC products since 2008.
            R-28 NOS has built in 6 pc CPLD programmable chipsets to separate the different configured circuits for avoid interrupt .
            The internal hardware design is fully controlled by complex software. A huge advantage is the fact the software in the FPGA/CPLD can easily be upgraded offering new features or improve the performance. Such design is much flexible and future proof!


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