Audio-GD – Master 9P MK2 – Dual mono balanced integrated power amplifier & headamp

HIGHLIGHTS

• Integrated Amplifier = 2x 70 Watt RMS @ 8 ohms
• Headphone Amplifier = 2x 14W @ 40 ohms
• Neutral and Vacuum Valve sound like selectable
• ACSS Non Negative Feedback Amp
• “Linear Fidelity” Technology
• Soft Start Power Design

SPECIFICATIONS

ACSS  Technology

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 .

NON FEEDBACK

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.

POWER SUPPLY

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 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 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 MK2 is applied a four channels digital control relays based volume control. .Master 9P MK2 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.

CHASSIS & SHIELDING

Master 9P MK2 has complete separation of left, right amplifier channels, power supply, and transformer.
Master 9P MK2 uses heavyweight all-aluminum alloy chassis to prevent the eddy current of transformers from interfering on circuit board.