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Master-10 MK2

Real Balanced ACSS Non Negative Feedback Integrated Power Amp
Dual Mono Design
Applied "Linear Fidelity" Technology
Soft Start Power Design
Can custom order built in DC blocker
Weight around 40KG

Price: USD2790
( Exclude shipping cost . Include metal remote controller that  need two AAA batteries support by users .)  
Organic glass top board price  : USD30
  

Custom order one group input bypass preamp ,price +USD30 , leadtime 2 workdays.
Please send your address, name  to audio-gd@vip.163.com get the quote.

DC blocker available for custom order:
       Because the product has the low impedance transformers design , if the power line (120V or 230V) has serious disturb , usually will has the low voltage DC in the power line, cause the transformers have the vibration and cause the noise.
       Even though in the same serious disturb in the power line , the high impedance transformers design can without vibration and noise , for example the R core, EI core or high impedance design O core transformers.
       But for the power amp, the high impedance transformer design has effect and degrade on sound dynamic, bass impact and control .
       Because the serious disturb power line is rare, based on the customers feedbacked, it has around 10% users meet with serious disturb  , so our power amps have not include the DC blocker . If customer has experience on vibration and noise in last power amp model, customer can custom order the DC blocker , it can kill 1.2V DC of the power line which is enough for most case.
        Price is USD40.

The non negative feedback output drive stages had applied "Linear Fidelity" technology (Appling for patent):

       The Master 10 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 together.
　

         Below diagrams had show the distortion on the Master 10.
         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-10 MK2 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-10 MK2 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 has 0.015% distortion at 20KHz , the below diagram has 0.0018% 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 .
         We test 5 unit products, the performance is similar ,we post the worst diagrams in below .

THD+N at 8 ohm 10W

THD+N at 8 ohm 50W

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 .
5 analog inputs:  RCA X2, XLR X2, ACSS X1
Four channel 99 steps digitally controlled relay-based volume control avoids channel imbalance and improves sound quality.
Applies 24 pieces of ON Semiconductor  transistors, every piece has 15A/230W performance. Supports 250W X2 (8 Ohms) output.
The capacitance of the whole machine reaches as high as 140,000 uF, with two 750W circle core  and two R cores transformers (Total 1500W)  and separate power supplies for the right channel and left channels.
A total of 4 groups of high-quality class A parallel connection PSU's supply the gain stages.
Applies all audiophile grade components, including DALE resistors, WIMA caps, custom order NOVER (UK brand) caps, all audiophile grade input & output sockets and gold IEC socket.
Real dual mono design, the Left and Right channels had been separate by the shield board.

Detail of the Current Conveyor Technology

Core:
               Master-10 MK2 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-10 MK2 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-10 MK2 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-10 MK2 applies four channels of diamond non-feedback output stages composed of 24 pieces of ON Semiconductor  transistors, every piece has 15A/230W performance . The capacitance of the whole machine reaches as high as 140,000uF. Two transformers are used with total power of 1500W.
            
Input: 
              Master-10 MK2 can input not only XLR balanced signal and RCA single end signal, but also the top grade ACSS current signal. No matter what kind of signal it is input, it is able to transfer it to balanced current signal and amplify it.

Shield and avoid vibration:
             Master-10 MK2 uses heavyweight all aluminum alloy chassis to prevent the eddy current of transformers from interfering with the circuit board.  The interior is separated into 2 sections with aluminum boards for the best separation off the ACSS parts, the output stages and transformers. The AC power wire is shielded by a copper channel from back to front.

             Master-10 MK2 take care the vibration for the best sound playback. Each channels gain parts under a 5MM thick aluminum board, these aluminum board not only poise the heat between cool and hot amps, our workers care to install all transistors cling the aluminum board for avoid the vibration cause the sounding worst. From our testing, with the aluminum board bring clear detail reproduce and less harsh than take off the aluminum board .
                          

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-10 MK2 , 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  output stages offer the very low output impedance to drive the speakers .

            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-10 MK2 is applied a four channels digital control relays based volume control .Master-10 MK2 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-10 MK2 allow users select between 99 steps exponential characteristic volume control , whatever volume control allow users smooth to control the volume level . 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.

Components:
         Uses all audiophile grade components, including DALE resistors, WIMA caps, custom order NOVER (UK brand) caps, all audiophile grade input (Neutrik) & output sockets (CMC) and gold IEC socket.  Master-10 MK2 has all parts of four channels exact-matched before installation.