Audio-gd products had design and test based on the AP SYS-2722 (The top-drawer professional equipment in world)



Summarize
Class A design built by discrete analog stages without any OPA or coupling caps in the signal channels.
Non- feedback ACSS and output stage designs
Total applied 4 pcs exact matching 150W  transistors  offer the strong power output
Class A output 3500MW at 25 ohm ,drive most headphones can working under pure class A state
40W transformer ,Class A  PSU's for  DC supply.
Uses most Hi-end grade parts and exactly matched transistors, OCC wires.
6 DB and 16DB gain can drive the high and low sensitivity headphones
3 groups input:  RCA X2, ACSS X1
Preamp output :   RCA
Headphone amp output:     6.3MM X1
　

Technology detail

Detail of the Current Conveyor (ACSS) Technology

Impedance matching:
             There are a lot different DACs in worth, they had different design and output impedance . For avoid the sound quality effect by different DAC's output impedance, in the NFB-3AMP, it had design a pair single-ended class A FET buffers in the input . All the RCA input signals through these FET buffers, the output impedance had become very low, even the source had high or low output impedance.
             The FET buffers working on pure class A state, and it is so short signal journey , it can keep the sound quality without coloration ,dry and harsh .
             

Core:
             NFB-3AMP had the same ACSS design  . It is a class A design built by discrete analog stages without any OPA or coupling caps in the signal channels.
             They seem complex , but in fact they are the most simple design the world has ever had , their a lot components to process the power supply. The simplest and shortest signal journey brings out the most neutral and least colored sound.

            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.
            All signal gain is in current area, all transistors work in pure class A mode.
            The NFB-3AMP has all components  exactly matched before installation.
             Super low THD （Test by AP SYS-2722,0DBV output level)      Flat frequency response （Test by AP SYS-2722)
                                                                 

Strong class A output stages:
             The NFB-3AMP had design a pare diamond difference output stages, every parts had exact matching before assemble so don't need any human adjustment . 
             The output stages had  two pair 150W transistors ,they also working under class A state .

             

Power supply:    

           The class A parallel connection PSU has very high input impedance to avoid pulse through the PSU from affecting the preamp and low output impedance with very fast speed and high linear, so it is a very clean power supply.
            The NFB-3AMP applies seperate linear PSUs for the display and control parts, avoid the disturbances through power line from affecting the amplifier.
           

Components:
      Uses all Hi-end grade components, including DALE resistors, WIMA caps, custom order NOVER (UK brand) caps.