Built In 4 Groups of  DA-8 V2 Modules
Built In FPGA Processor to Reject Jitter 
DSD , DXD 32bit / 384K Support From USB / HDMI
Built in real balanced headphone amp.
Built with OCC and Hi-end parts

Please not:
          The R-28 had built in fully dedicated discrete R-2R resistor ladders DA modules. Based on some users feedback from Audio-gd other's R-2R products, it need longer burn in time to achieve the best sound quality and performance.
          Even it had burn in over 100 hours before shipping , but we are advice customers burn in it more than another 500 hours.
          You can power on it with playing music but shut down the volume for quickly finished burn in if you are at home.
          The mini remote shipped without battery because the either DHL and EMS limit shipping by plane , customers want to buy one CR2025 battery and assemble in the remote.



Input mode: 
Push the button "Input" for select the input sources .
Input 1: HDMI-IIS input.
Input 2: USB input.
Input 3: Optical input.
Input 4: RCA - coaxial input.
Input 5: RCA analog input.
Input 6: XLR analog input.

Gain mode: 
Push the button "Gain", the display will show between " L, H" .

"L" mean the unit working on low gain (100 steps and 7DB).

"H" mean the unit working on high gain (100 steps and 17DB).
We have applied the new gain technology ,no any switches,relays or parameter of the amp change while change the gain modes so the sound quality is exact same in different gain modes. Users just want to choice the better mode for easy adjust the volume level.



Output mode: 
Push the button "DAC/HP", the display will show between " P , H".

"P" mean the unit output from XLR / RCA / ACSS from rear. XLR and RCA can connect to two amps in same time.

"H" mean the unit output for headphones on front plate.

The DAC/PREAMP output mode selector : 
Pull out , XLR / RCA /ACSS output as decent DAC, in this mode, the display show "d" instead "P" and the volume number show "--" ,the volume can not adjust anymore (The headphone output mode has not effect).
Push into , XLR / RCA /ACSS output as preamp .
Headphone output mode has not any effect by this selector .


 

Warmer sound setting : 
The unit had built in a lot setting in the FPGA for users select the best suite sound flavors but they only effect the digital inputs.
Push into 4 pcs jumper for got the warmer sound flavor. It is effect for all inputs.

           R28_V3 firmwares function introduce.

        
　

How to active the digital setting mode:
         The "DAC/HP" and "Input" buttons has dual functions.
         While the input between input 5 and input 6, the "DAC/HP" button can select the output mode between "H" (Headphone output) and "P" (Preamp output) .
         While the input is between 1 to 4, the "DAC/HP" button become dual functions.
         In case, push the "DAC/HP" button one time, the left first display flashing around 3 seconds, in term if the "DAC/HP" button has not push again, the output mode change either "H" or "P".
         If the "DAC/HP" button push again while the left first display flashing, the unit go into the digital setting mode.
　

Important warn:
         Before push the "DAC/HP" button, we are advice user turn  low  the amp volume, stop the music track playing .
         Because for the aim to reproduce the best sound quality, the DAC without mute design , change the setting may output circuit switch sound .
         Around 5 seconds after non any button had push, the display stop blink, user can click the music track to playing and  turn up the volume.

DAC/HP button :
          While the unit had went into the digital setting mode, the one digit display will blink for active the function setting , push the "Input" button can change function .
         While the display blink, push "DAC/HP" again , the right next one digit display will blink for setting .


Left 1st display : Oversampling 
         "O" for select oversampling, "N" for select NOS mode.


Left 2nd display : OS and NOS modes
          While OS setting on "O" mean the DAC working under oversampling mode, lower number OS modes sound became warmer and smoother. Or depend on your sense .
         Mode "0" : class technology NOS mode.
         Mode "2" : 2X oversampling.
         Mode "4" : 4X oversampling .
         Mode "8" : 8X oversampling.

         While OS setting on "N" mean the DAC working under NOS mode, it has one mode now, it is the full new NOS configure design.

Left 3rd display : (Simulate SAA7220 +TDA1541A sound) :
           Active (1) : Simulate SAA7220 +TDA1541A, digital attenuation low to -55DB, was -130DB. Bitwide low to 16bit , was 24 bit. While active this function, I are advice setting to OS2 or OS4 mode. But infact, this function can working with any setting mode.
　

Left 4th. display :  (Syn version for correct HDMI data, Asy version for Dith)
          Syn version : If the HDMI input had noise, distortion or some samplings no sound, user can setting the 1st number ON (1) or OFF (0) to fixed the issue. In default is OFF (0) .
         Asy version : Active (1) or Disable (0)  dither for all inputs.

Left 5th. display : Display
         Active (1)  the display auto dark, the display will become dark in around 10 seconds after stop operate any buttons . Disable (0) the display auto dark, the display  light always.

"Input" button:
           While the display non blink, for select the input sources.
          While the display blink, for setting the digital process functions.

       
HDMI definitions : (Compatible with PS audio standard)
Pin 1 :       SDATA -                     
Pin 2 :       GND                         
Pin 3 :       SDATA +                    
Pin 4 :       SCLK +                       
Pin 5 :       GND                         
Pin 6 :       SCLK -
Pin 7 :       LRCK -                        
Pin 8 :       GND                         
Pin 9 :       LRCK +
Pin 10:      NC    (Syn version still need the Mclk+ on this pin)           
Pin 11:      GND                         
Pin 12:      NC    (Syn version still need the Mclk- on this pin)   
Pin 13:      NC                            
Pin 14:      NC                           
Pin 15:      NC
Pin 16:      NC                            
Pin 17:      GND                         
Pin 18:      NC
Pin 19:      NC
R28_tda_Asy don't need MLCK input . Even the source has MLCK output but has not effect .




R28_tda_Asy and R28_tda_Syn firmwares
What's the different between R28_tda_Asy and R28_tda_Syn:
       R28_tda_Asy is the firmware  running in asynchronous mode, after update it can without input the Mclk signal from HDMI-IIS input, regenerative inside by the Accusilicon clocks.
       R28_tda_Syn is the firmware running in synchronous  mode, it still need the Mclk signal from HDMI-IIS input.
        Some users may don't concern the technology different, they just concern the sound and they know the technology advantage don't mean the sound better .
       In the simple, you can consider R28_tda_Asy is the Accurate version and the R28_tda_Syn is the Smooth version.

Firmware update guide:
     R8 update guide (R28update guide same as R8)