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New figure :      9 types digital filter users setting.
What's advantage of setting the digital filter characteristic:
Except the NOS DACs , all DACs have applied the digital filter, the digital filter characteristic effects the sound quality and flavors. Most DACs have the fixed digital filter characteristic maybe not the best taste for the users. The NFB-2 and NFB-3 have 9 types  digital filter characteristic for users find the best sound of personal sense.
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NFB-2
Dual WM8741 inside
ACSS /RCA output DAC
Coaxial/Optical/USB input
24Bit / 96KHz USB input and
24Bit / 192KHz Coaxial/Opitcal support


Price:
NFB-2   USD450 
NFB-3   USD300 (Exclude shipping cost)
Weight: Approximately 5kg
Dimension:  W240 X L300 X H80(MM)
Accessories: Stock power cable X1,stock optical cable X1,USB cable X1

Summarize: Fully discrete amp without any OPA , couple caps ,non- feedback analog output stage and non-feedback Class A power supplys .
       The NFB-2 uses a 50W R-core transformers. The power transformers and rectifiers are carefully shielded from the electric field of the power transformers and rectifiers' frequency transmission. More than 20,000uf 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 GDs requirement. A total of 7 PSU groups are used to purify the power supply. To achieve Silent operation, the control circuit is powered with separate regulator.
       The DAC NFB-2 uses mostly DALE and Vishay resistors,  WIMA capacitors. The electrolyte capacitors are custom ordered from NOVER (a UK brand), and exact-matched transistors. RCA sockets are custom ordered and 24k gold-plated. All transistors are Toshiba and Hitachiand Hitachi.

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/forum/thread/512856/audio-gd-nfb-2-nfb-3-delivery-impression-thread/30

http://www.digitalaudioreview.net.au/index.php/audio-reviews/digital-source-reviews/item/177-audio-gd-nfb-2-dac-19-series


http://www.head-fi.org/products/audio-gd-nfb-2-and-nfb-3/reviews
Note: The S/PDIF interface default applied WM8805 (192KHz support), if you want replace the  DIR9001 (96KHz support) by free ,tell us  while place the order please.

What's different between these popular chips
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@ Dual WM8741 ES9018 AD1955 AD1852 WM8740
SNR 128 DB (Mono) 120 DB 120DB 114DB 117DB
DYNAMIC RANGE 128 DB (Mono) 129 DB 120DB 114DB 117DB
NFB-2
    
                
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Please note:
All audio-gd products have change to new ACSS sockets as below ( expect the Master series ) , some photos maybe not update yet.

            
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9 types digital filter users setting

Please note:
     Please shut down the NFB-2/3 and pull off the power cable then make the setting change.

2X oversampling , Minimum phase 'soft-knee' filter.
Up to 192KHz support. 

2X oversampling , Linear phase 'soft-knee' filter.
Up to 192KHz support.

2X oversampling , Linear phase 'brickwall' filter.
Up to 192KHz support.

4X oversampling , Minimum phase 'soft-knee' filter.
Up to 96KHz support.

4X oversampling , Linear phase 'soft-knee' filter.
Up to 96KHz support. 

4X oversampling , Linear phase 'brickwall' filter.
Up to 96KHz support. 

8X oversampling , Minimum phase apodising filter.
Up to 48KHz support. 

8X oversampling , Linear phase apodising filter.
Up to 48KHz support. 

8X oversampling , Linear phase half-band filter for backward compatibility.
Up to 48KHz support.

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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 2006, have evolved the technology to include all audio signals in our systems from the digital source to the power amplifier. Since 2005, ACSS comp5nts have become Audio-gd's most popular products.


About NFB?

     
NFB mean Non-Feedback .
       The NFB-2 applies two pcs newest Wolfson high-end  DA chip WM8741 which can support up to 32Bit/192KHz input. Compared to other WM8741 designs, Our NFB-2 applies Non-feedback ACSS output stage for I/V conversion, and Non-feedback power supply for the whole gear.
       The ACSS is a non-feedback technology made with 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.
       The output buffers are Non-feedback, for low impedance, we applied a two-stage parallel connection, the output impedance is only 20 ohms.
       The DAC is 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 ).
       (Note: While users want to replace the DIR module, please power off the NFB-2 and pull off the power cable at first )
 
Click image to enlarge.       

 
       NFB-2 applies the excellent 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.
        The NFB-2 uses 6 groups of high-quality class A parallel connection PSU with dedicated DC supply.
       The class A parallel connection PSU has very high input impedance for avoid pulse through the PSU from affecting the DAC and low output impedance with very fast speed and high linear , so it is a very clean power supply. In my experience, its sound is better than battery power supply, better human sound and neutral.

 
          
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functions:
     
Front plate:
      Left button: power ON/OFF switch.
      The knob:
Select built-in DAC source between USB, coaxial and optical.
      Right button: Choose between RCA and ACSS output configure. (Owners can choose this button anytime.)


FAQ:

1, What's different between NFB-2 and NFB-3.1?
    
The main differences are as follow:
        1, The NFB-3.1 applies 2 groups of
class A parallel connection PSU supplied for analog output stage, (the analog output stage power supply is very important, so we keep the 2 groups of class A parallel connection PSU here). Another 5 groups of linear PSU's supplied for other parts. The NFB-2 applies 6 groups class A parallel connection PSU for the whole gear, and 1 linear PSU for the control parts.
         2, The NFB-3.1 applies
a toroidal transformer, the NFB-2 applies an R-core transformer.
         3, The NFB-3.1 applies mostly 1% SMD resistors and caps, the NFB-2 applies mostly DALE resistors and WIMA caps.
         4, The NFB-3.1 have digital filter setting by software, the NFB-2 have digital filter setting by hardware.

            NFB-2              NFB-3.1
         
     

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Choice of power cable appropriate for your country:

    When you place the order , please let us know the type of power cable you require.

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NFB-2 Specs

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

RCA Output
S/N Ratio:>113db
Output Level:2.5V

Frequency Breadth:20-20KHz



ACSS Output
S/N Ratio:>116db
Output:.1.2MA

Frequency Breadth:20-20KHz


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