Why there are a few jumpers in the digital part?
        DAC NFB-1 has a few jumpers in the digital part, some customers may believe this is a wrong design. But I definitely say no. The NFB-1 is designed to separate the digital ground and the analog ground, some design will used a inductance to connect these two grounds, but I think the inductance has a specific frequency characteristic which is not good for audio equipment. In our design, we applied a 0 ohm jumper to connect these two grounds, even though the jumper has 0 ohm, in the high frequencies it still has impedance to insulate the effects between digital and analog ground.

 ES9018 based DAC is the third edition design:
         A lot of customers recommended ES9018 to me one year ago, during this year I made a lot of practice, at Jul. 2009, I finished the first edition and spend lot months to test and audition. At Mar. 2010 , The second edition finished. The regular edition finished at Jul. 2010.
  Click image to enlarge.   

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.

         NFB mean Non-Feedback .
        The NFB-1 applies the newest ESS high-end Sabre32 DA chip ES9018 which can support up to 32Bit/96KHz input . Compared to other ES9018 designs, Our NFB-1 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.
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        NFB-1 applies the excellent DA chip ES9018 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-1 uses 5 groups of high-quality class A parallel connection PSU with dedicated DC supply.
        Two groups of +15V and -15V for the ACSS analog output stages, two groups of +3.3V and +1.2V for the ES9018 , and one +5V for the coaxial and optical receivers.
        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.
      

　

If I only use the RCA output, is the NFB-1 wasted or not fully utilized?

           The NFB-1 is a real balanced output DAC, it has XLR (balanced), RCA (single-ended), and ACSS output. There are 4 ACSS modules in the NFB-1 for balanced output, and all the ACSS modules have balanced input, so even through RCA output, the ES9018 DA chip will perform fully.
　

NFB-1 Specs

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


RCA Output
S/N Ratio:>113db
Output Level:2.5V
Frequency Breadth:20-20KHz


XLR Output
S/N Ratio:>116db
Output Level:5V
Frequency Breadth:20-20KHz

ACSS Output
S/N Ratio:>120db
Output:2MA
Frequency Breadth:20-20KHz