NFB-9
(The upgrade version of the NFB-8)

DAC with / without volume control  & preamp output level
Full functions remote control
Dual WM8741 inside
ACSS / XRL / RCA output balanced DAC
AES / Coaxial / BNC / Optical / USB input
Supports up to 24Bit/192KHz

Price:    USD1390 (With volume control)
              USD1330 (Without volume control)
              USD1480 (With volume control and preamp analog inputs)
 (Exclude shipping cost)
Weight: Approximately 15kg
Dimension:  W430 X L430 X H93(MM)
Accessories: Stock power cable X1,stock optical cable X1,USB cable X1

What's new in NFB-9: Fully discrete amp built on motherboard for best neutral sound and better detail.
       With 48 steps exponential characteristic I/V conversion volume control , applied four channels digital control relays  based volume control to avoid channel imbalance and avoid sound quality degrade , max output level up to 2.5 - 2.5V (XLR  ), can drive power amp direct without preamp.

Summarize: Fully discrete amp without any OPA , couple caps ,non- feedback analog output stage and non-feedback Class A power supplys .
       Uses three R-core transformers (135W total) separate power supplys for the digital part , right channel and left channel.
       More than 50,000uf audio grade NOVER capacitors are used to ensure ample and smooth power feed.
       A total of 15 class A  PSU groups are used to purify the power supply. To achieve high S/N, the control circuit is powered with separate regulator.
       Uses most Hi-end grade parts and exact match transistors.

Sound Characteristics:  "Neutral but smoothness sounding ,it doesn't sound skeletal or digital (or metallic). There's meat aplenty on them bones . It's a sigma-delta DAC chip implementation without the dryness, neutrality without the emotional disconnection" - John Darko

Feedback :
http://www.head-fi.org/t/529882/new-audio-gd-NFB-8-wm/105#post_7711879

Flavor button:
Select the oversampling and digital filter response of the NFB-9 .

Power button:
For power ON/Off the NFB-9 .
　

Selector button:
Select the input channel of the NFB-9.   
Display 1 : AES input.     Display 2 : BNC Coaxial input .    Display 3 : RCA Coaxial input .  Display 4 : Optical input.  Display 5 : USB input.
　

Volume Down and Up buttons (The volume control only applied for XLR and RCA output ) :
1. After powering on the NFB-9, immediately after the display has flashed "NFB-9" three times and flashed the display as last power off ,
       A , If you push and hold the "volume down" button for one second, the NFB-9 will forget the volume level set before you last powered off and set the volume at zero.
       B, If you push and hold the "volume up" button for one second, the NFB-9 will be at the volume it was last set to before the power was switched off.
       C, If you push and hold the "flavors" button for one second, the NFB-9 will be at the volume on maximum 2.5V output level ( The standard DAC output level ).
2. Push once for the volume to go up or down 1 step.
3. Push and hold to make the volume go up or down quickly.
　

Power socket:                    
AES socket:        
BNC coax socket:     
RCA coax socket:      
Opt socket:               
USB socket:             
DAC out sockets:             
　

For power input.
For AES input (channel 1).
For BNC coaxial input (channel 2).
For RCA coaxial input (channel 3).
For optical input (channel 4).
For USB input (channel 5)..
For dedicated DAC output from RCA / XLR  and ACSS . (The XLR and RCA output  with volume control ).

About ACSS:
     ACSS (Audio-gd Current Signal System) is Audio-gd's system for transmitting audio signals in the current domain. This concept, first seen in 1966, we have used for many years, and since 2005, have evolved the technology to include all audio signals in our systems from the digital source to the power amplifier. Since 2006, ACSS comp5nts have become Audio-gd's most popular products.
　

About NFB-9
    NFB means Non-Feedback.
             The NFB-9  applies the newest  high-end dual WM8741 which can support up to 24Bit/192KHz input (AES , Coaxial and optical input support up to 192KHz ,  USB support up to 96KHz/24bit). Similar to other WM8741 designs, Our NFB-9  applies Non-feedback ACSS output stage. The dual WM8741 feed to the ACSS output stage without any OPAs so it can avoid sound coloration .
             The ACSS is a non-feedback technology made with fully discrete amplifiers. Most people know the global feedback design can offer better specs in test measurements, and non-feedback can't do well in test measurements but can offer better sound for the human's ears. Here is a conflict of the classic circuits. But the ACSS opens a new field, it can offer a least coloration sound which is more neutral with very low distortion and high linearity. So it can retain the dynamics, detail and neutral sound but not sound bright or harsh.
            In most design, the WM8741  feed to a difference voltage amp through voltage signal . In NFB-9 , the dual WM8741 has feed to the ACSS parts direct through balanced current signal . The current signal mode can  bring the best signal of the DA chips .
            The output buffers are Non-feedback. For low impedance, we applied the dual FET buffer output stage which is quite less colored than most conventional circuits.
            The two OPAs in the NFB-9 just for DC serve to keep the output DC offset at zero , allow the DAC analog parts are without couple caps to avoid coloration.
            The 24/96 USB interface outputs a I2S signal to dual WM8741.
            Applied the WM8805 as the SPDIF interface , its sound characteristic is same with the WM8741 which is detail but smooth, and it can support up to 192KHz input.  The WM8805 had quite low jitter (50PS),much less than the CS8416 ( 200PS ).
            Real fully balanced discrete design.
   
      
           
        

         NFB-9 applies the excellent dual DA chip WM8741 and excellent analog output stages, but these are not the only keys of the best sound. The power supply is most important. Even applying the best DA chip and the best amp, if matched to a normal power supply, the total sound may still be average or sound musical, but can't be neutral and detailed. That is why it is easy to find hi-end grade gears maybe without the best chips or amp stages, but with plenteous dedicated DC supply circuits.
         Uses three R-core transformers (135W total), one 35W R-core supplies power for digital parts, another two 50W R-cores supplies power for analogy parts. The power transformers and rectifiers are carefully shielded from the electric field of the power transformers and rectifiers' frequency transmission. More than 50,000uf audio grade NOVER capacitors are used to ensure ample and smooth power feed. The NOVER capacitors are specially custom order from NOVER (U.K.) according to Audio GD’s requirement.
         The NFB-9 uses total 16 groups PSU .  The 15 groups of high-quality class A parallel connection PSU with dedicated DC supply double-stage PSU, which can offer very clear DC power for the DAC , producing a very black background and neutral sound characteristic. The double-stage PSU is very important for digital parts. Some designs may have very low jitter in theory, but if the power is supplied by a dirty or low-speed power supply, it will increase the jitter and pollute the data, and degrade the sound quality obviously.
         The class A parallel connection PSU has very high input impedance to avoid pulse through the PSU from affecting the DAC and low output impedance with very fast speed and high linearity, so it is a very clean power supply. In my experience, its sound is better than battery power supply, better human sound and neutral .
         To achieve high S/N,  the control circuit is powered with separate regulator.
        The massive  all double stages PSU power supply.  
  

 Uses most Hi-end grade parts
          Uses mostly DALE and Vishay resistors,  WIMA ,EVOX capacitors and a lot SOLEN caps. The electrolyte capacitors are custom ordered from NOVER (a UK brand), and exact-matched transistors. RCA sockets are custom ordered and 24k gold-plated, the power socket is RA 24k gold-plated. Neutrik balance sockets and Canare BNC socket .All transistors are Toshiba and Hitachi.

 The I/V conversion volume control without sound degrade:

           Usually the volume control in the DAC   has either ways to implement .
           Way 1, The volume control implement in the digital parts . But  reduce every 6DB volume had to lost 1 bit of the D/A convert ,  so even though built in a 32 bit DA chip, in fact maybe only listen with 16 bit while listen by low volume level.
           Way 2, The volume control implement in the analog parts output through a volume pot to reduce the volume . but the volume pots quality effect the sound quality direct , the low quality volume pot cause lost the detail and channels imbalance cause the soundstage distortion  . And even the high performance volume pot still cause the detail lose.
           Both ways are degrade on sound quality.
           So in the NFB-9 , we applied the I/V conversion volume control , the volume control just  a variable passive I/V conversion , so it can't degrade on sound quality in every volume level . After the volume , there are four groups  dual FET non-feedback buffer output stages offer the very low output impedance .
            The volume control quality is much important in the real balance gear . It must guarantee the four channels signal control exact to achieve the performance of the real balance gear .  If the cool and hot of the balance signal can't guarantee exact, the balance output will has large distortion cause the sound quality and performance even much worst than a single end gear waste the  balance gear  design and the cost.
           In NFB-9 is applied a four channels digital control relays based volume control. NFB-9 has 48 steps exponential characteristic volume control allow users smooth to control the volume level .NFB-9 has two relays volume boards (total four channels) through changing the DALE resistors to control the volume for avoid channels imbalanced ,achieve the best performance and sound quality of the gear.
           Exact four channels digital control relays based volume control.
         

 If I only use the RCA output, is the NFB-9 wasted or not fully utilized?
      The NFB-9 is a real balanced output DAC, it has XLR (balanced), RCA (single-ended), and ACSS output. There are 4 ACSS amps in the NFB-9 for balanced output, and  balanced input, so even through RCA output, the dual WM8741 DA chips will perform fully.

NFB-9 Specs

mprovement may result in changes in specifications and
design without notice.

RCA Output
S/N Ratio:>119db
Output Level:2.5V (with / without volume control)
Frequency Breadth:20-20KHz



XLR Output
S/N Ratio:>122db
Output Level: 2.5 - 2.5V  (with /without volume control)
Frequency Breadth:20-20KHz

ACSS Output
S/N Ratio:>127db
Output:2.0MA
Frequency Breadth:20-20KHz