Price:  (Exclude shipping cost)
Master 9PS (Smooth edition) : USD1850
( Assemble 8 pcs Toshiba every pc with 15A /150W output transistors .For who like the sound warm and smooth )
Master 9PN (Neutral edition) : USD1899
( Assemble 8 pcs ON Semiconductor every pc with 15A /230W output transistors .)For who like the sound neutral and transparency. )
( Exclude shipping cost . Include combo remote controller that can control the product and some lot audio-gd latest DAC models . It need two AAA batteries support by users .)  
  
Custom order : Custom order one or some inputs without volume control , work as the pure power amp for speaker and headphone. Free now.

Please note: Before the Master 9P release , a customer advised the Master 9P Headphone output sockets are the 4pins XLR X3 / 6.3MM X1, after shipped some units the customers said least 30% hifiers still apply the dual 3 pins headphone output so the Master 9P will assemble 3pins XLR X2 / 4pins XLR X1 /6.3MM X1

Please send your address, name to audio-gd@vip.163.com get the quote.

Is the 70W+70W enough?
        The Master 9P has 70W+70W at 8 ohms, even with 60W  output , the THD+N  still  low to 0.055% at 1KHz and 0.004% at 20KHz, much lower than some power amp at 60W output but declare 150W max power .
       Usually the transistor built in power amp had been recommend the actual output power is around 1/5 to 1/3 of the max power output for keep the distortion as low , so the Master 9P can work as well as some  200W power amps .
       For the home audio system,  if the speaker with lower than 86DB sensitivity , the listen room usually around 20 square meters , if the listen room is larger , the speaker usually has higher than 88DB sensitivity , for these situations, 1W / each channel avg. power already can make the speaker for normal listen , even with the quite loud listen , 5W / each channel avg. power already can boost close 100DB on the 88DB sensitivity speaker . In the case the Master 9P still has 14x times spare power.
       Of course there is no doubt for drive any headphones.

Summary
Real dual mono design .
Fully balanced design, the gain stages and pre-driver stages work in class A, built with discrete analog stages without any OPA or coupling caps in the signal channels.
The output transistor stages have supper excellent linear, it sound like the pure class A design but without the high heat of the pure class A design .
Applies 8 pieces of ON Semiconductor  transistors ,every piece has 15A/230W performance (Master 9PN). Supports 70W X2 (8 Ohms) output, 14W X2 (40 ohms) .
The capacitance of the whole machine reaches as high as 100,000 uF, with two circle core in total 600W power ,which is larger than some 200W power amps  .
A total of 4 groups of high-quality class A parallel connection PSU's supply the gain stages.
Two gain modes with 100 steps exponent character volume control , high gain has 34DB, low gain has 20DB, no problem drive any high or low sensitivity headphone and speaker.
5 groups input: RCA X2, XLR X2, ACSS X1
Speaker output *1 pair
Headphone amp output: 3pins XLR X2 / 4pins XLR X1  /6.3MM X1
Headphone output options with neutral and simulate vacuum sound for customer selects on the front plate

The non negative feedback output drive stages had applied "Linear Fidelity" technology :

       The Master 9P had applied the "Linear Fidelity" technology on the output drive stages . The output drive stages had not negative feedback but can keep the distortion low and steady, and had the ultra excellent  linear performance.
       In some lot power amp designs, the distortion had big different level on different power output level , even on one power output level, the full frequency band's distortion level had quite different , especial the low and high frequency .
      The blue line of below diagram show the distortion to frequency at 8 ohm 20W output of an well known power amp which worth around USD10k. 

       The below diagram show the most musical instrument frequency bands . The frequency band had cover from 20Hz to 4KHz .
       Different distortion must effect on the sound . For example, if playing piano music recorder, cause by the larger different distortion on the frequency band, you can hear the low frequency band like playing a brand A piano, the middle frequency band like playing a brand B piano, and the high frequency brand like a brand C, the music recorder like the different brand pianoes  playing and edited together.
　

         Below diagrams had show the distortion on the Master 9P.
         The negative feedback applied, most is for reduce the distortion.
         Some people dislike the negative feedback design on the power amp, it reduce the distortion but make the listen unpleasure.
         The negative feedback power amp had good distortion result on emulational load measure, but while connect the real speakers, the electric potential of the speaker can through the feedback loop feed to the amp input stages cause the larger distortion.
         The negative feedback power amp even reduce the distortion , but the distortion increase while output power increase, this cause the larger dynamic music sound become harsh and fire to your face while listen the music.

         Usually the non negative feedback design has high distortion and difficult to control, especial the drive output stage which is work under strong current state.
         In the Master 9P design, the gain stages have applied the ACSS technology, it is the non negative feedback design but it's native advantage has very low distortion.
         The output drive stages had applied the " Linear Fidelity " technology .

         The overall design in the Master 9P is non negative feedback design.
          From the diagrams, the amp has quite flat and steady distortion on the frequency band from 20Hz to 5KHz, keep the same sounding character while playing the musical instruments .
          The distortion roll off a lot start at 5KHz, even lower than some amps which is depend on the negative feedback , it obvious show the supper linear performance of the amp.
         Compare the diagram, the upon diagram of the USD6K amp has 0.015% distortion at 20KHz , the below diagram has 0.002% distortion on 20KHz.
        The ultra low distortion had not depend on the negative feedback, but depend on the ultra linear of the amp, so it's sound very transparency and analogue.
         On the different output power level , the amp has similar distortion level, while listen with softer and dynamic music,  it offer the same sound character without harsh .

THD+N at 8 ohm 20W (<0.055% at 1K, <0.002% at 20KHz)

         Even with 60W output , it still offer the low distortion.
THD+N at 8 ohm 60W (<0.055% at 1K, <0.005% at 20KHz)

        The Master 9P has very wide frequency band that allow the signal output has very low phase distortion , offer the most transparency but analog sound . But please not,  you must match it with the good DAC and source and speaker / headphone , because it is so revealing , it can't give you the good sound if match with the USD30 DVD player .
Frequency band at 8 ohm 1W  (-2.5DB at 200KHz)

　

Detail of the Current Conveyor Technology

Core:
           Master-9P is a true balanced design applying the newest ACSS design which can improved the XLR connection to sound as good as the ACSS connection. It seems 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 Master-9P power amp only has a single " voltage" gain stage to process signals, but works in ACSS mode so in fact it is a current gain stage instead of voltage gain stage, whereas normal OPA chips already include two or three voltage gain stages. The simplest and shortest signal journey brings out the most neutral and least colored sound.
           Master-9P applies ultra-low distortion single stage ACSS amplifier and soldered directly on the motherboard . The gain stages and pre-driver stages working on class A .
           The output transistors stages working on high idle current state . The diamond cross output stage design can avoid "switch distortion" as good as the class A amp .
           The ACSS is a non-feedback technology made with fully 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, achieved by the unique, superb open-loop multiple output current mirror. Incomparably precise and ultra-low distortion in the gain signal is the result. The signal path is balanced throughout and all transistors work in class A mode.
           The ACSS parts use 4 groups of high-quality class A parallel connection PSU for dedicated DC supply. The class A parallel connection PSU has very high input impedance to avoid pulse from the PSU from affecting the gain stages, and low output impedance with very fast speed and high linear, so it is a very clean power supply.

Drives:
          Massive use of high power parts and robust power supply guarantee vigorous current output that drives most existing loudspeakers.
         Master-9P applies four channels of  non-feedback output stages composed of 8 pieces of ON Semiconductor transistors, every piece has 15A/230W performance. The capacitance of the whole machine reaches as high as 100,000uF. Two transformers are used with total power of 600W.
        
Impedance matching:
              There are a lot different DACs in world, 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 Single polarity 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 .

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 9P , 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 .
             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 9P is applied a four channels digital control relays based volume control. .Master 9P has total four channels through changing the tolerance 0.05% resistors to control the volume for avoid channels imbalanced ,achieve the best performance and sound quality of the gear.
                          
Shield: 
         Master 9P has complete separation of left, right amplifier channels, power supply, and transformer.
          Master 9P uses heavyweight all-aluminum alloy chassis to prevent the eddy current of transformers from interfering on circuit board.