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NFB-10.32]USB applied USB-32^
Discrete  DAC+ Headphone amplifier / Preamplifier

32bit / 384K Asynchronous Transfer  USB-32 Chip
Built in 2 Pieces Hi-end grade WM8741 Chips

Price:   USD549  (Free remote control )   
Extra metal remote :  USD50        

Accessories : Power cable and USB cable . If customers want optical cable please inform while place the order . The free remote control without warranty. )


Summarize Use Manual Specs Technology Detail Custom Option Shipping Cost

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.
            NFB-10SE uses the latest high-end Dual WM8741
which can support up to 32Bit/192KHz input. Similar to other WM8741 designs, NFB-10SE applies Non-feedback ACSS output stage. The Dual WM8741 feeds to the ACSS output stage without any Operational Amplifier (OPA) so it can achieve very neutral sound.
            The ACSS technology is a non-feedback technology made with fully discrete amplifiers. Most people know that the global feedback design offers better specifications in measurements than non-feedback design. However, non-feedback design offers better sound for human ears, which is a drawback of the conventional circuits. But the ACSS technology opens a new era, it offers the least coloration sound which is very neutral with very low distortion and high linearity. It retains the dynamics, details and neutrality but does not sound bright or harsh.
           The output buffers are also non-feedback. In order to maintain low impedance, we applied a diamond output stage which is quite less colored than most conventional circuits.
           The analog stage does not use couple cap to avoid coloration.
           The 32bit/192KHz USB interface outputs an I2S signal to the Dual WM8741.
           NFB-10SE applies the WM8805 as the SPDIF interface; its sound characteristic is the same as the WM8741, which is detailed and smooth and supports up to 192KHz.  The WM8805 has quite low jitter (50PS), which is much lower than the CS8416 (200PS). Users can choose the DIR9001 module as the SPDIF interface instead of WM8805. The replacement is very easy thanks to its modular design.

                         Real fully balanced discrete design.


      NFB-10SE applies the excellent Dual WM8741 and excellent analog output stages, but these are not the only key to the best sound. The power supply is the most important. Even the best DA chip and the best amplifier design have applied, if matched with an average power supply, the resulting sound quality may still be musical but can't be neutral and detailed. This is why it is easy to find that the best neutral hi-end gears might not have the best chips or amplifier stages, but with plenteous dedicated DC supply circuits.
          NFB-10SE uses a high performance transformer. More than 38,000uf audio grade NOVER capacitors are used to ensure ample and smooth power feed. The NOVER capacitors are specially custom made from NOVER (U.K.) according to Audio GD's requirements. 
          NFB-10SE uses 7 groups of high-quality PSUs with dedicated DC supplies. Digital and analog voltages each have isolated internal power regulations.
          The analog amplifier power supply is more important for sound reproduction. In NFB-10SE, the +15V and -15V for the ACSS analog stages are supplied by high speed discrete PSUs. They can offer pure and quick power supply for driving headphones faithfully with high S/N. The high voltage power supply can drive most headphones ranging from 15 to 600 ohms as well.
          To achieve high S/N, the control circuit is powered with separate regulators.

                              Strong power supply.

 The I/V conversion volume control without sound degradation:

           Usually the volume control can be implemented in the DAC + amplifier combo in two methods
           Method 1: The volume control is implemented into the digital stage. The major drawback is that 1 bit of the D/A conversion is lost in every 6DB volume reduction. So, even though the built-in DA chip is 32 bit, in fact, only 16 bit may be left at low volume level.
           Method 2: The volume control is implemented in the analog amplifier input stage through a volume pot to reduce the signal level. However, the volume pot affects the sound quality adversely. A low grade volume pot loses the details and creates channels imbalance resulting into soundstage distortion. Even a high grade volume pot inevitably loses the details. Both methods degrade the sound quality.
           So, NFB-10SE applies the I/V conversion volume control, the volume control is just a variable passive I/V conversion being placed at the ACSS amplifier output, where the output is current signal but not voltage signal. I/V conversion is to change the volume level from the current (I) signal to the voltage (V) signal. (Like R-2R D/A chips output passive I/V conversion) It can keep the signal frequency band flat while not losing any detail. It does not degrade the sound quality in every volume level. In front of the volume control, there are four groups of diamond non-feedback buffer output stages that offer very low output impedance.
            Mark Levinson also knows that current volume control has great benefits, so in the volume control of his top grade hi-end preamplifier No.32, he uses many components to change the voltage (V) signal to current signal (I), then through the R-2R network to control the volume, and finally changes back to voltage signal (V) again. NFB-10SE simply works in current (I) signal domain, and technically, it is superior to the conventional technology due to less conversion.
            The volume control quality is much more important in a real balanced gear. It must guarantee the signals of the four channels are exactly the same to bring out the benefits of a real balanced gear. If the cold signal and hot signal of a balanced gear are not exactly the same, the balanced output will has a large distortion causing the sound quality and performance even much worse than a single end gear. This is a waste of a balanced design and the additional cost.
            NFB-10SE applies digitally controlled relay-based volume control in 96 steps. It has 48 steps in both high gain and low gain mode to allow users to control the volume level smoothly. NFB-10SE has two relay-based volume control boards (totally four channels) through changing the DALE resistors to control the volume to avoid channel imbalance, achieving the best performance and sound quality of the gear.

Precise four-channel digitally controlled relay-based volume control.




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