The NFB-11 applies the newest ESS high-end Sabre32 DA chip ES9028 which can support up to 32Bit/384KHz input .
To be achieve the best performance of ES9028 , must work in current output mode. in voltage output model, there is -12DB THD+N loss .
The standard current model design usually need 3 amps (OPA) , the first amp implements I/V conversion, the ES9028 output current signal to voltage signal .
The second amp is responsible for conversion balanced signal ,to single-ended signal and implement the low pass analog filter , then go through the volume control fed to the third amp, (the headphone amp ).
Every amp usually have two gain stages built in to the ES9028 chip . Signal must go through total of 6 gain stages and finally arrive at the output stage.
The NFB-11 applies Non-feedback ACSS design. The ES9028 feed to the ACSS circuit without any OPAs .
The ACSS circuit naturally working in current mode . The ACSS amp only have one current gain stage , the ES9028 output signal only goes through one stage .
The shortest signal path can reproduce the best detail and dynamics almost without any sound coloration .It showes the real performance of the ES9028 dac.
So our ACSS design is the best combo with ES9028 to achieve the best performance .
Upper is the diagram of a standard ES9028 headphone amp design. The bottom is the NFB-11 design .
The ACSS also 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 to the human's ears. Here lyes a conflict of the classic circuits.
But the ACSS opens a new field, it can offers the least coloration to the sound which is more neutral with very low distortion and high linearity. So it can retain the dynamics, detail and neutral sound ( not bright and harsh )
The output buffers are Non-feedback. For low impedance we applied a diamond output stage which is less colored than most conventional circuits. It is built with 4 pcs 20W (in total 80W) high speed Toshiba transistors, To early drive mostly the headphones.
The DAC is without de-coupling caps to avoid coloration. There are two OPAs built in as the DC servo to control offset .
The 32bit / 384K USB interface outputs a I2S signal to the ES9028 .
Fully Discrete ACSS headphone amp.
NFB-11 applies the excellent D/A chip ES9028 and excellent analog output stages, but these are not the only elements to the best sound. The power supply is a key element . Even when applying the best D/A chip and the best amp, if matched to a average power supply, the total sound characteristics may still be average at best ,maybe musical but can't be neutral and detailed. That is why it is easy to find hi-end gear without the best chips , but with plenty of dedicated DC supply circuits.
The NFB-11 uses 6 groups of high-quality PSUs with dedicated DC supply . Digital and analog voltages each have separately isolated internal power regulatiors.
The digital power had 4 groups high speed PSU groups( double stages PSUs) this allowes to avoid the interruption from the power supply that can cause the jitter . It offers blacker background and much cleaner sound. In addition this double stages PSUs are only applied in our USD1500+ products.
This massive power supplie design is usually only applied in the USD1000+ products .
The analog power supply is more important for sound reproduction . In NFB-11 the +15V and -15V for the analog output stages are high speed Discrete PSUs. They offer pure and quick power supply to drive any headphone with high accuracy .The high voltage power supply can drive most headphone from 15 to 600 ohms as well.
Strong power supply.
About volume in ACSS circuits:
Volume control is very important.
In ACSS, it is placed at the ACSS module output, where the output is the current signal stage not the voltage stage . 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-11 is simply a more complete work in terms of the current signal, and technically, it is superior to conventional technology.
ALPS 27 volume pot
| Output Level
Headphone output : 10V RMS
Variable output : 5V Max
Fixed output: 2.5V RMS
(Only for headphone.)
1 ohm / Headphone output
2 ohm / DAC output
0.5 Vp-p(75 Ohms, Coaxial)
19 dBm (Optical)
Support Operate Systems (USB)
Windows, Mac,Linux, Iphone & Ipad
|| USB model: 44.1kHz-384kHz，DSD64-512
Coaxial model: 44.1kHz-192kHz
Optical model: 44.1kHz-96kHz
20Hz - 20KHz （-0.1DB）
1 Version 100-120V AC 50/60 Hz
2 Version 220-240V AC 50/60 Hz
|W180 X L220 X H55(MM, Fully aluminium ,with feet)
AC power cord X1
USB cable X1