The NFB-11 applies the newest ESS high-end Sabre32 DA chip ES9038 which can support up to 32Bit/384KHz input .
To be achieve the best performance of ES9038 , must work in current output model, in voltage output model, there is -12DB THD+N worst .
The standard current model design usually need 3 amps (OPA) , the first amp implement I/V conversion, conversion the ES9038 output current signal to voltage signal .
The second amp is the difference amp, conversion the balance signal to single-ended signal and implement the low pass analog filter , then through volume control feed to the third amp, the headphone amp .
Every amp usually have two gain stages built in so the ES9038 signal must through total 6 gain stages arrive the output stages .
The NFB-11 applies Non-feedback ACSS design. The ES9038 feed to the ACSS circuit without any OPAs .
The ACSS circuit naturally working in current model and have design difference current input , it can process the I/V conversion, signal difference and headphone amp in current model in one ACSS amp . And this ACSS amp only have one current gain stage , the ES9038 output signal only through one stage can arrive the output stages .
The shortest signal journey can reproduce the best detail and dynamic, and almost without sound coloration , It can show the real performance of the ES9038 .
So our ACSS design is the best combo with ES9038 achieve the best performance .
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 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. It built with 4 pcs 20W (in total 80W) high speed Toshiba transistors, no matter to drive the most headphones.
The DAC is without couple caps to avoid coloration. There are two OPAs built in as the DC serve to keep the DC offset .
The 32bit / 384K USB interface outputs a I2S signal to ES9038 .
Fully Discrete ACSS headphone amp.
NFB-11 applies the excellent DA chip ES9038 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 average 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 , but with plenteous dedicated DC supply circuits.
The NFB-11 uses 6 groups of high-quality PSU with dedicated DC supply . Digital and analog voltages each have separately isolated internal power regulations.
The digital power had 4 groups high spend PSU group double stages PSUs , can avoid the interrupt from the power cause the jitter increase, offer the blacker back stage and much pure sound. In ago, double stages PSUs only applied in our USD1500+ products.
This massive power supplies design usually only applied in the USD1000+ products .
The analog power supply is more important for sound reproduce, in NFB-11, the +15V and -15V for the 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.
In ACSS, it 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-11 is simply a more complete work in terms of the current signal, and technically, it is superior to conventional technology.