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( 2017 version .Since 1st.May )

The single ended design based on Master 9
Class A PSUs built in
Discrete  Headphone amplifier / Preamplifier
3000mW at 25 ohm (Class A )
8000mW at 40 ohm
OCC and hi-end parts applied

Price: USD450  (Exclude shipping cost)
Please send your address, name to
audio-gd@vip.163.com get the quote.



Free mini remote controller (not in warranty)


Use Manual


Custom Option

Shipping Cost

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

Since 4th. April 2018,   the model had upgrade the volume ports:
The upgraded volume ports had built with Vishay or KOA resistors with dual resistors parallel ,  tolerance low to 0.05% .

Different to the NFB-1AMP:
The C-2 is a single ended  headamp and preamp (+/- 30V DC high voltage power supply ), The NFB-1AMP is balance  headamp and preamp (+/-15V DC power supply ).  So They had same output power specs can drive most headphone as well.
If customer like to keep your headphone with single ended connector (6.3MM), choice the C-2 get better performance than the NFB-1AMP.
If customer had the balance connector headphone or can modify the headphone with balance connector, choice the NFB-1AMP.

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 just same as our top grade Master 9
Total applied 4 pcs exact matching 150W  transistors  as the pure class A output stages
3000MW at 25 ohm Pure Class A   ,drive most headphones can working under pure class A state, 8000mW at 40 ohm max output, no matter with the low sensitivity headphones
+/- 35V DC high voltage power supply built in, Class A  PSU's for  DC supply.
Uses most Hi-end grade parts and exactly matched transistors, OCC wires.
100 steps digitally controlled relay-based volume control avoids channel imbalance and improves sound quality .
Supper Exponential Volume Characteristic,  easy match the volume with very high sensitivity headphones and speakers
10 DB and 19DB gain can drive the high and low sensitivity headphones
5 groups input:  RCA X4, ACSS X1
Preamp output :   RCA / RCA / ACSS
Headphone amp output:    4pins XLR X1 /  6.3MM X1
Static storage mode control software for avoid disturb sound quality , the MCU output once control data and save in the perform parts ,then stop output data until users next operation.


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 C-2, 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 .


             C-2 had the same ACSS design with our top grade model Master 9 . It is a pure 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 C-2 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 C-2 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 offer 3000MW at 25 ohm  Class A   ,drive most headphones can working under pure class A state, 8000mW at 40 ohm max output, no matter with the low sensitivity headphones


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 C-2 applies seperate linear PSUs for the display and control parts, avoid the disturbances through power line from affecting the amplifier.


Volume control:
           The volume control is also different from conventional technology. Conventional volume control technology is the volume control implement in the analog amp input stage through a volume pot to reduce the signal  . The volume pots quality effect the sound quality direct , the low quality volume pot cause lost the detail and channels imbalance cause the soundstage distortion  . Even the high performance volume pot still cause the detail lose. Whatever quality volume pots, must cause the S/N worst .
       But in the C-2 , we applied the I/V conversion volume control , the volume control just  a variable passive I/V conversion place at the ACSS amp 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 R-2R D/A chips output passive I/V conversion)  It can keep the signal frequency band flat and not lost any detail. It can't degrade on sound quality in every volume level . After the volume , there are four groups  diamond non-feedback buffer output stages offer the very low output impedance  .
            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 implement the volume control , and then change back to voltage signal (V) again.
            But C-2 is simply a more complete work in terms of the current signal, and technically, it is superior to conventional technology.
The less conversion bring much neutral sound .
            In C-2 is applied a  digital control relays based volume control. .C-2 has total two channels through changing the DALE resistors to control the volume for avoid channels imbalanced ,achieve the best performance and sound quality of the gear.
           C-2 have 100 steps volume control,  very smooth control  for  both high / low sensitivity headphone and speakers. While users change the volume, the
combine relays break or close, it may had slightly switch sound on output and disappear while stop change the volume.
C-2 Supper two sets Exponential volume characteristic  

Static storage mode control software:
          In most control softwares design, the MCU will continuously output data to the perform parts , the MCU had the very high speed, so the output data become high frequency impulses disturb the audio signal circuits make the sound worst . 
This product had applied static storage mode control software  , the MCU output once control data and save in the perform parts while just power on and users operate  ,then stop output data until users next operation. This design make the sound quality improve on the clear and transparency .


         The C-2 design had not compromise , it's built by full aluminum chassis, the transformer interference can't through the aluminum chassis transfer to the analog amps, and there are two shield boards for insulate the transformer and the power supplies.

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




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