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Master 9

Real Balanced ACSS design 
Pure Class A  (9W @ 40 ohm)
Preamp & Headphone amp
Super Exponential Volume Characteristic
OCC and hi-end parts applied , no upgrade option necessary

Price: USD1430  (Standard version)
            USD1510 (Custom version for HE6)
( With metal remote, exclude shipping cost . The custom version for HE6 and low sensitivity headphones only, if for other high sensitivity headphones may had too much gain ,few steps volume may had quite loud.)

The unit can working well and safe to position it on vertical or horizontal. Leave least 2CM room on its original top side while it is on vertical state.

             

                    
Summarize Use Manual Specs Shipping Cost


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


The unit applied input short design :
Nowdays a lot high and middle range preamps, headphone amps and integrated amps had applied the input short design .
Without the input short design , if the amp connect to multi-ply sources and all source had playing , different sources will had the signal crossing cause the sound quality degrade .
For example, the input 1 connect to a DAC and the input 2 connect to a CDP, while both had playing, the CDP signal will crossing to the input 1 , mix with the DAC signal cause the sound degrade.
In world there are more than 99% DACs and the sources had allow the outputs short , if your DAC decalre can't short the output , please custom order the amp without input short , but in the case , while you connect multi-ply sources, you are better only let one power on and others power off for avoid the signal crossing .


Summarize
Fully balanced pure class A design built by discrete analog stages without any OPA or coupling caps in the signal channels.
Non- feedback ACSS analog output stage.
Total applied 12 pcs exact matching 150W transistors ( In total 1800W )  as the output stages and PSU stages for implement large class A output power .
Uses three R-core transformers (In total 135W ) separate power supplies for the digital  control components, right and left channels.
More than 55,000uf audio grade NOVER capacitors are used to ensure ample and smooth power delivery.
A total of 9 groups of  PSU's for dedicated DC supply.
Uses most Hi-end grade parts and exactly matched transistors, OCC wires.
Four-channel 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 headphone / speaker without change the gain mode.
20DB gain can drive the low sensitivity headphone very well.
5 groups input:  RCA X2, XLR X2, ACSS X1
Preamp output :   XLR / RCA / ACSS
Headphone amp output:    4pins XLR X1 /  3pins XLR X2 / 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.
 

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Modification guide on headphone jack for 4-pin balanced headphone output.
  
Click here to read:   modification guide

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Technology detail

Detail of the Current Conveyor 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 Master 9, it had design 4 groups expensive class A FET cascode  buffers in the input . All the  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:
             Master 9 is a true balanced design applying the newest ACSS design which can improve the XLR connection to sound as good as the ACSS connection. 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.
             Master 9 applies ultra-low distortion single stage ACSS amplifier and soldered directly on the motherboard. It is a fully class A preamp / headphone amp and applies class A power supplies.

            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, all transistors work in pure class A mode.
            The Master 9 output buffers had applied 4 pair power transistors ( 150W / 15A ) working on pure class A state,  the output impedance is only 1 ohms , it can drive most headphones and amps as well  .
            Master 9 has all components of four channels exactly matched before installation.

Strong class A output stages
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             The Master 9 had design 4 groups diamond difference output stages as the balance drive stage, every parts had exact matching before assemble so don't need any human adjustment . 

             The output stages had  four pair 150W transistors ,they also working under pure class A state , the balance output mode had 4X times power than the same state single-ended mode .The pure class A design had larger  drive ability than the specs, it drive the headphone not worst than a double power class AB design , not to refer, the pure class A is the best sound design  in worth. The balance drive mode can kill the noise and distortion in the end of the headphone, much improve the sound stage, background and the transparency ,ect.

             


Power supply:    
           Three special transformer are used to supply power separately for the audio and control circuit.
            Master 9 uses 8 groups of high-quality  PSU .
            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.
            Master 9 applies seperate linear PSUs for the display and control parts, avoid the disturbances through power line from affecting the amplifier.

Input/Output:
           Master 9 can input not only XLR balanced signal or RCA unbalanced signal, but also the top-grade ACSS current signal. It can also output RCA signal, balanced XRL signal, ACSS current signal to the power amplifier. Using RCA input, Master 9 can convert to balanced ACSS signal and output real balance signal from XLR and ACSS.
           The ACSS input / output can compatible with KRELL CAST products and SATRI technology gears . The XLR /  RCA can compatible with any audio devices in world.
           Master 9 can output RCA, XLR and ACSS at the same time in preamp output model , in headphone amp model, Master 9 can output XLR ,single end for headphone.
           The input channels of Master 9 adopt separated shielding method. When switching, the idle signal lines linked to the equipment and the ground wire are completely disconnected. The idle input ports of the equipment are shielded. In that case, the sound quality won't be affected even with more connected equipment.
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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 Master 9 , 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 Master 9 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 .
            The volume control quality is much important in the real balance gear . It must guarantee the four channels signal control exact to achieve the performance of the real balance gear .  If the cool and hot of the balance signal can't guarantee exact, the balance output will has large distortion cause the sound quality and performance even much worst than a single end gear waste the  balance gear  design and the cost.
            In Master 9 is applied a four channels digital control relays based volume control. .Master 9 has total four channels through changing the DALE resistors to control the volume for avoid channels imbalanced ,achieve the best performance and sound quality of the gear.
            Master 9 have 100 steps volume control, control range achieve 90DB (usually the steps volume ports, potentiometer volume port, relays base volume control all have around 70DB range  ), very smooth control range on first 50 steps , cooperate with 20DB high gain, so can very easy adjust the volume for  both high / low sensitivity headphone and speakers.
While change the volume, the different relays break or close, it may had slightly switch sound on output and disappear while stop change the volume.
             
Supper Exponential volume characteristic                   The Volume steps comparison to normal volume knob       
                                                                            
            
Shield: 
         Master 9 has complete separation of left, right amplifier channels, power supply, and transformer.
         Master 9 uses heavyweight all-aluminum alloy chassis to prevent the eddy current of transformers from interfering on circuit board. 

Components:
         Uses all audiophile grade components, including DALE resistors, WIMA caps, custom order NOVER (UK brand) caps, all audiophile grade input & output sockets (Neutrik ) and gold IEC socket.  Master 9 all parts of four channels had exact match before install.

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 .

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