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NFB-12.1

Discrete  DAC+ Headphone amplifier / Preamplifier
Built in 2 Pieces Hi-end grade WM8741 Chips

NFB-12.1 Price:  USD215

NFB-12.1
   
        
  
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About ACSS technology:
         ACSS (Audio-gd Current Signal System) technology is Audio-gd's signature technology for transmitting audio signals in the current domain. This concept, first seen in 1966, has been adapted by us for many years. Since 2005, we have been evolving this technology to include it into all audio signal transmissions in our systems from digital source to power amplifier. Since 2006, ACSS technology became Audio-gd's signature technology and gains a lot of popularity.

About NFB?
         NFB means Non-Feedback.
         The NFB-12 applies the newest  high-end dual WM8741 which can support up to 24Bit/192KHz input (AES and Coaxial inputs support up to 192KHz , USB and optical inputs support up to 96KHz/24bit).. Similar to other WM8741 designs, Our NFB-12 applies Non-feedback ACSS output stage. The dual WM8741 feed to the ACSS output stage without any OPAs so it can achieve very neutral sound quality.
         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.
         The output buffers are Non-feedback. For low impedance, we applied a diamond output stage which is quite less colored than most conventional circuits.
         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 ).
                         
                           Fully
Discrete ACSS headphone amp.
                           

        

         NFB-12 applies the excellent dual 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-12 uses 6 groups of high-quality PSU with dedicated DC supply. Digital and analog voltages each have separately isolated internal power regulations.
         The analog power supply is more important for sound reproduce, in NFB-12, the +15V and -15V for the ACSS analog output stages are high speed Discrete PSU. They can offer pure and quick power supply for driving the headphone exactly. The high voltage power supply can drive most headphone from 15 to 600 ohms as well.

 
        Strong power supply.
                

About volume in ACSS circuits:
     
For a headphone amp, the volume control is very important.
             NFB-12
uses ACSS technology, which is very different from conventional technology.
            The volume control is  is placed at the ACSS modules output, where the output is the current signal, not the voltage signal. The volume control is I/V conversion, and the volume depends on the current (I) conversion to the voltage (V). (Like D/A chips output I/V conversion)
            As you can see, ACSS circuits have no gain, as it is a completely different circuit.
            The sound quality benefits from I/V conversion volume control. Mark Levinson also knows that current volume control has great benefits, so in their Top End preamp NO.32 volume control, they use many components to change the signal to current signal (I), then through the R-2R network to control the volume, and then change back to voltage signal (V) again. But NFB-12 is simply a more complete work in terms of the current signal, and technically, it is superior to conventional technology.
  
                  
      
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