DEMO - Xindak XA8800MNE

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The circuit features of XA8800MNE

Designed as a separate mono-channel structure, XA8800MNE is a full symmetrical current negative feedback Class A amplifier. The main circuit theory and technical features are as following:

The input buffering amplifying stage adopts fast and wide-frequency amplifying circuit with cross coupling compensatory structure. It could connect the push-pull amplifying dynatron as Darlinton circuit and control base current at a low level, ensuring the stabilization of the middle point voltage. Meanwhile, the adoption of transistor Constant Current Source as load ensures the steady and liable work on the stage.

Darlinton complex structure on the Voltage amplifying stage not only ensures enough voltage gain but also raises the input impedance to reach excellent match between the different stages. Besides, the adoption of Cascode circuit offers a good solution of the effect on the high frequency by the transistor junction capacitance. Thus the frequency width could be raised, the output characteristic curve of the bipolar transistor could be improved, the distortion of this stage could be reduced and high stabilization could be achieved.

On the current drive stage, it adopts high power FET to supply drive current for the end stage. The parallel output transistors on the end stage could reduce the output impedance, increase the output power, and improve the load capability with low resistor.

The static working current of 6 pairs high power transistors on the end stage as parallel output is about 300mA and each transistor works in the special linear area where current is higher. This could eliminate crossover distortion and switch distortion efficiently and reduce the output impedance. Equipped with impedance compensatory network including L、Rs、Rz and C on the output terminal, the load of this unit will be closer to pure resistor and difficult to cause self-excitation. Meanwhile, it could afford bigger damp to enhance the controlling ability of this unit to the loudspeaker.

In order to ensure the middle point voltage of this unit approximately to be zero, high quality operating amplifying components, high frequency non-inductance resistor, silver isinglass capacitance and so on are put to good use to the loop current servo feedback circuit.

As for the power supply for the complete unit, each channel adopts 600W high quality annular transformer while the other parts adopts winding group on the power supply separately. Additionally the power supply for the power amplifying, voltage amplifying and protecting circuit are separated: the power supply for the power amplifying part is equipped with 50A bridge rectifier and 60,000MF filtering capacitance and supplies power directly after commutating and filtering; the power supply for the voltage amplifying adopts stable power supply with fast speed, low noisy, low impedance and strong ability to avoid the “ripple” to avoid the modulating disturbance caused by fluctuation of the power on the following stage and make the sound purer.

Additionally, this unit adds protection functions, including power-on delay concussion protection, zero point floating on the output terminal, over current and over voltage of the power transistor protection. In order to avoid the noisy when power-off, this circuit adds transient release circuit, power-on delay circuit and glittering indicating circuit for protection to make this unit more intellective.

Sound Features of this unit:

Because XA8800MN is a current negative high power Class A amplifier, the sound of this unit is very thick, mellow, sweet and warm with high transparency and high speed. The extension on high frequency is very clear and exquisite, the taste and analysis of music are very excellent in middle frequency and in low frequency the flexibility and sense of weight are very clear. Generally speaking, the sound is fast, strong and clear, especially when performance the baritone and mezzo-soprano.

• Separate mono channel structure
• Current feedback Class-A amplifier
• High power FET as the drive
• 6 pairs of metal-packaged transistors as parallel output
• 600W high quality transformers
• 50A bridge rectifier along with high capacity power filters
• 2mm gold-plated PCB
• Warm and thick sound with full taste of music

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