Wisdom in mind,   enthusiasm at heart.

NFB-28 (Version 2015 )
(The best mid range DAC +amp we ever had)
Discrete  DAC+ Headphone amplifier / Preamplifier
With XLR / RCA analog inputs
DSD , DXD support from USB & I2S Input
32bit / 384K Sabre ES9018
32bit / 384K Asynchronous Transfer  USB-32 Chip

Please note:
         In USB model, start the computer then power on our product is necessary because our products have not applied the USB+5V for less interrupt from the computer.
        

Discontinued the analog idle input short circuit function:
         The unit  had design the analog idle input short circuit (In 5 and In 6) for avoid the disturb between different sources.
         This design also applied in a lot high end brand devices.
         The working theory :  Without the idle input short circuit ,if the input 5 and input 6 had connect two extra DACs,  while users select the either input 5 and input 6 , the another input signal will fire through the circuits and mix  into the using signal, even though this signal is  weak  but still can degrade on the sound quality.
          With the idle input short circuit function : if user select either the input 5 and input 6, the another input signal will short circuit then no any signal fire through circuits , can keep the sound quality had not degrade.
       Below case users want to discontinued the idle input short circuit function, pull off the 4 jumpers as mark on the photo:
      1, The same extra source not only connect the unit analog input, but connect with other amps simultaneity.
      2, The same extra source connect to the unit input 6 and input 5  at simultaneity.
          

How to set the NFB-28 DAC output level?
         Turn the volume of the external amp to proper position, then turn the NFB-28 volume to the sound had proper loud.

DAC/HP button:
Select the output modes.
         H:   Headphone output.
         P:   Preamplifier output. 
　

Gain button:
Select the Fast / Slow volume control characteristics.
        H: Fast.  64 steps range.  
        L: Slow. 100 steps range.
　

Please note:
Since 3rd. March 2015, the DAC/HP button setting to " D"  and Gain buttons setting to "F" at same time , the unit's RCA, XLR and ACSS outputs set to as DAC fixed output mode, output level is 2.5V on RCA, 5V on XLR, 2MA on ACSS .
If your amp had not volume control, please don't setting the DAC/HP to "D" and the Gain to "F " at same time.

Since 15th . April 2015, upon function had remove.

Selector button:
Select the input sources.   
        1: USB input.
        2: I2S input . 
        3 : Optical input.
        4 : Coaxial  input.
        5 : Analog RCA input.
        6 : Analog XLR input.

Volume knob:
        Turn Left :     Reduce the volume.
        Turn Right  : Increase the volume .
        Because different sources may have different output level, so before select the input sources, reduce the volume is more safe .
　

I2S-RJ45 input format:
( 3.3V level ,  we can't guarantee the I2S input can cooperate with all I2S output devices.
( The I2S transmit want to take care the transmit cable  )
Pin 1 : SDATA
Pin 3 : LRCK
Pin 5 : SCLK
Pin 7 : MCLK
Pin 2,4,6,8 GND
 Customer can custom order the different define of the I2S  pins free .
Please note: Don't hot push / pull of the I2S cable. Any time must power off the units then push or pull the I2S cable.

About the DSD CTR input:
      If the users want to play the DSD music through the I2S input, users except connect the I2S cable, but want to connect the DSD CTR input to the source DSD CTR output at same time.
      If the DSD CTR had not connect to the source, push into the short plug please. It is shipping with the unit.
     The DSD CTR cable price is USD10, 0.5 meter length.

Gain button:
Select the Fast / Slow volume control characteristics.
        H: Fast.  64 steps range.  
        L: Slow. 100 steps range.
        F: (Full ) High gain mode. 100 steps range. (For the low sensitivity headphone like the HE-6 or the source had low output voltage level)
        S: (Super)High gain mode. 64 steps range. (For the low sensitivity headphone like the HE-6 or the source had low output voltage level)

The button on rear : Pull out for the DAC / preamp without volume control , Push into for the DAC / Preamp with volume control. The headphone output always had the volume control. Please operate the button while the unit power off .

The display auto dark :  Push into the jumper is auto dark .Please operate the jumper while the unit power off .

Digital filter setting：
SET ： Push into the jumper is NOS, pull off is Oversampling . Available of PCM signal input from USB or I2S .Please operate while the unit power off .
IIR0 与IIR1：Available for DSD input .
                 IIR0                       IIR1
50K         Pull off                    Pull off
60K         Pull off                    Push into
70K         Push into                 Pull off

FIR ： Push into for setting Slow roll off , pull off for setting Fast roll off . Please operate  while the unit power off .


DSD / PCM support from I2S input :
The DSD/PCM support not only from the USB input, but the I2S input.   The NFB-28 can detect the I2S input signal, if input DSD signal, it will auto to remove the DSD pop noise while select the DSD track . (Had test working well with Amanero and Xmos U8 ) .