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 2005, have evolved the technology to include all audio signals in our systems from the digital source to the power amplifier. Since 2006, ACSS comp5nts have become Audio-gd's most popular products.
NFB mean Non-Feedback .
The NFB-3 (384K) applies two pcs newest 384KHz 32bit DA chips PCM5102 ( Coaxial and USB) . The NFB-3 (384K) applies Non-feedback ACSS output stages .
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 the dual FET buffer output stage which is quite less colored than most conventional circuits, the output impedance is only 10 ohms.
The two OPAs in the NFB-3 (384K) just for DC serve to keep the output DC offset at zero , allow the DAC analog parts are without couple caps to avoid coloration.
The 32/384 USB interface outputs a I2S signal to dual PCM5102.
Users can choice the DIR9001 module as the SPDIF interface instead WM8805, the replace is so easy without solder , only pull off and push into .
(Note: While users want to replace the DIR module, please power off the NFB-3 (384K) and pull off the power cable at first )
Fully discrete design.
NFB-3 (384K) applies the excellent DA chip 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-3 (384K) uses a high performance R-core transformer. The power transformers and rectifiers are carefully shielded from the electric field of the power transformers and rectifiers' frequency transmission. More than 30,000uf audio grade NOVER capacitors are used to ensure ample and smooth power feed. The NOVER capacitors are specially custom order from NOVER (U.K.) according to Audio GD’s requirement.
The NFB-3 (384K) uses 7 groups of high-quality PSU with dedicated DC supply.
The analog output stages are power supplys with the class A parallel connection PSU.
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.
To achieve high S/N, the control circuit is powered with separate regulator.