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HE-2 MK2
Regenerate power supplys with separate 4 blocks
30W pure class A , 250W class A at 8 ohm each channel
Supports XLR and ACSS inputs
Apply Real balanced ACSS non negative feedback power amp
Apply "Linear Fidelity" technology non negative feedback output stages
Soft start power design
80 pcs ONsemi (Motorola) output transistors
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Summarize Use Manual Specs Shipping Cost

Price:  USD6660     (1 set with 4 blocks .Exclude shipping cost . )
1,The user that purchased and using audio-gd Master series power amp can provide the series number when place the order .
2, The product has burn in 500 hours before shipping cause the leadtime is long .)
3, The DC power cable length 50CM in default , if need longer cable, please custom order .
4, The rear of the regenerate power supply chassis built with organic glass, no fonts on it, if care , don't order it please.

Recommend match with HE-1 preamp with the most reallike sound  :  http://www.audio-gd.com/HE/HE-12017/HE-12017EN.htm

Compare to Master 2H:
       We tried two pair Master 2Hs working in Bi-Amps mode, compare to one pair HE-2MK2 working in the normal mode, in our opinion that the HE-2MK2 still better sound quality overall than the two Master 2Hs.
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About the DC blocker :
       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 toroidal 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 feedback, it has around 10% users encounter with serious disturb  , so our power amps have not include the DC blocker .
       For avoid the sound quality degrade, the HE-2 MK2 can not custom order built in the DC blocker, if users have the DC disturb cause the transformers' hum, please order the external high quality outlet which built the DC blocker .

About the external power processor :
       Because the product built with regenerate power supply , we don't recommend connected to the active external power process like external regenerate power processor, isolate power transformers, voltage regulator ect, In the extreme case even the power has serious interrupt, use a good quality power filter outlet is enough .

Summarize:
Separate blocks regenerate power supply (The regenerate power supply for the gain boards )
Fully balanced design, the gain stages and pre-driver stages work in pure 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 .
2 analog inputs:  XLR / ACSS
Applies 80 pieces of ON Semiconductor  transistors. Each channel supports 30W pure class A and 250W class A (8 Ohms) output.
The capacitance of the whole machine reaches as high as 260,000 uF, with 6 unit transformers (Over 2000W)  and separate power supplies for the right channel and left channels.
A total of 8 groups of high-quality class A parallel connection PSU's supply
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.

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The non negative feedback output drive stages had applied "Linear Fidelity" technology :
       The HE-2 MK2 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. 
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       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 pianos edited together.
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         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 HE-2 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 HE-2 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 0.002% 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 .
        Below diagrams had show the distortion on the HE-2 MK2.
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THD+N at 8 ohm 10W: approximately 0.03%

THD+N at 8 ohm 50W: approximately 0.04%

THD+N at 8 ohm 100W: approximately 0.05%


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Pure analogous Regenerative power supply :
        The regenerative power supply like a proprietary electric generator built in the unit.
        It can block most disturb from the power line , supply the ultra clean power supply for the audio amps , reproduce the most neutral and analog sound like audio signal for the system and the users.
       In the regenerative power supply design, the AC power through the regenerative input transformer , conversion to DC power ,through the class A PSUs power supply for the regenerative wave generator and driver stages .
       A balance regenerative regular wave generator produce the ultra low distortion 50Hz wave ,through the balance  gain amps and the strong  output stages , drive the regenerative transformers produce the clean AC power supply feed to the separate class A PSUs power supply for the L and R channel preamps .
        The class A parallel connection PSU has very high input impedance to avoid disturb through the PSU from affecting the signal parts and low output impedance with very fast speed and high linear,  it is a very clean power supply.
         Audio-gd on the regenerative power supply design points  :
         1, Through analyzed the AP SYS-2722 ,do a lot practises ,test and listen , full analog design of the regular wave generator have much lower distortion than the digital generator.
         2, Digital drive stages have higher efficiency , but full analog drive stages have much better analog sound like .
         3, 400Hz regenerative wave have higher efficiency , 50Hz regenerative wave had much far away the human ears sensitivity area than the 400Hz, boost the sound have much better analog sound like.


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Core:
         HE-2 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 HE-2 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.
         HE-2 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.

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Drives:
         Massive use of high power parts and robust power supply guarantee vigorous current output that drives most existing loudspeakers.   
         HE-2 MK2 applies four channels of diamond non-feedback output stages composed of 80 pcs ON Semiconductor transistors. The capacitance of the whole machine reaches as high as 260,000uF. Six transformers are used with over power of 2000W.
     
Input: 
         HE-2 MK2 can input not only XLR balanced 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 current signal and amplify it.

Shield:
        HE-2 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 3 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.
        HE-2 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 .

                                                     

Components:
        Uses all audiophile grade components, including DALE resistors, WIMA & SOLEN caps, custom order NOVER (UK brand) caps, all audiophile grade input (Neutrik) & output sockets (CMC) and gold IEC socket. The output transistors are 80 pcs ON Semiconductor transistors.  HE-2 MK2 has all parts of four channels exact-matched before installation.


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