About NFB#
NFB mean Non-Feedback.
The NFB-2 applies two pcs newest Wolfson high-end DA chip WM8741 which can support up to 32Bit/192KHz input. Compared to other WM8741 designs, NFB-2 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.
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 ).
NFB-2 applies the excellent DA chip 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-2 uses 6 groups of high-quality class A parallel connection PSU with dedicated DC supply.
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 (no distortion) power supply. In my experience, its sound is better than battery power supply, better human sound and neutral.