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How to achieve high-fidelity headphone amplifier design

?In the audio preamplifier, ShuntRegulatedPush-Pull (SRPP) circuit has high gain, low distortion, low output impedance and other characteristics, can get excellent sound quality performance, and thus widely used in audio circuits. In the high-fidelity audio circuit, the tube amplifier because of its unique charm and music listening, has been the majority of audio enthusiasts favorite and attention. In recent years, high-fidelity headphones because of its ease of use and relatively low prices, by more and more music lovers and audio enthusiasts favor. In the family of high-fidelity earphones, headphone impedance from the low resistance, medium resistance to high resistance are distributed: such as love technology 271S rated impedance of 48, Beyerdynamic Dt48 rated impedance of 20, Sen Haier HD580, HD600, HD650 Rated impedance of 300 and so on. For high impedance headphones, usually need a special matching circuit, in order to show its excellent performance. Compared with beats by dre wireless the speaker unit for the speaker, the headset beats headphones for its drive circuit performance requirements more stringent. Compared with the transistor, the tube static operating point voltage is high, the resistance is large, more suitable for the output beats earphones swing, the current drive signal small. This feature makes the tube suitable for driving high-quality headphones with high quality requirements but low power requirements.

In the audio preamplifier, ShuntRegulatedPush-Pull (SRPP) circuit has high gain, low distortion, low output impedance and other characteristics, can get excellent sound quality performance, and thus widely used in audio circuits. In this paper, a design of a common cathode amplifier for the input stage, SRPP amplifier circuit for the output level of the headphone amplifier circuit. The micro-equivalent model is established for this circuit, and the reasonable device is selected. The corresponding parameters can be controlled by theoretical calculation, so that the amplifier can drive the headphones well.

Input level

Input level using a transistor transistor composed of common cathode amplifier circuit, the circuit schematic shown in Figure 1. In the figure, the resistors RL1, Rk1 and Rg1 are connected with the anode, cathode and gate of the tube, respectively, so that the tube can establish a stable operating point, with the appropriate gain and appropriate local negative feedback. V1 can choose the commonly used electronic transistor, such as single transistor ECC92, or dual transistor Cheap Beats By Dre ECC82, 12AU7, 5814 and other models in a tube transistor working principle and the transistor in the bipolar transistor is different, but similar to the FET, Voltage amplification device, the main parameters of the transconductance gm, internal resistance rp and amplification factor , and between the three meet:

3 output level

The output stage uses SRPP circuit, the tube can choose the appropriate internal resistance of the transistor, such as 6N6, E182CC, can also choose for power amplifier low power pentode, such as 6P15, 6P14, EL42, EL91, EL84, EL86.

General pentad resistance is large, high gain, in order to reduce the output impedance and gain, the need to connect the transistor into a transistor.

The output stage of the text selection of low-power pentode as the amplification device, beats headphones select the other models of the tube, you need to determine the parameters of the external components according to their own parameters and supply voltage VCC2. In Fig. 3, Rsg1 and Rsg2 connect the second gate and the anode of the pentaves V2 and V3, respectively, and thus become the triode mode of operation. Rk2 and Rk3 are connected to the cathodes of V2 and V3, respectively, to provide the appropriate gate negative pressure for the tube. RL2 represents the impedance of the load. Choose a different type of pipe, due to the difference between internal resistance and gain, when driving the headset work, there will be different sound performance, usually through the subjective sound quality evaluation to determine the choice of the tube.