TDA7294 drive high-fidelity power amplifier ----- TDA7294 AMPLIFIER

Keywords: TDA7294 Push high fidelity power amplifier TDA7294 drive high-fidelity power amplifier As shown in Figure 1, the promotion stage uses TDA7294, and the internal push level and output stage uses the field effect tube, powered by ± 40V, the output power is 70W (RL = 8Ω; THD = 0.005%), tone Delicate, good listening is excellent. Power output VT1, VT2 uses the mountains of the mountains and high power to the tube 2SA1394, 2SC3858. The principle of the circuit is as follows: The signal is passed by C1, R1 inputs the TDA7294 positive phase input terminal 3. R3, C3, C4 of the second feet of R7 and IC constitute a negative feedback network, and the closed loop gain of this amplifier is about 34 times. ⑨, ⑩⑩ is standby, quiet, due to the time constant of the first ruler RC network than the first, so that the shutdown machine is mute, avoiding the switch impact, C7 is a self-lifting capacitor. Figure 1 TDA7294 driven high-fidelity power amplifier Production points: 1. The tip of the metal cap and the heat sink (the metal cap is involved in the metal cap) between the metal cap and the heat sink. 2. The power transformer is 400W double 20V, 50V / 10000μF filter capacitor, 50 V / 100μF, and 100 V / 0.1μF. The power supply part should be tested separately, first dispensed with the power, measure the power supply positive, whether the negative output voltage is symmetrical, the error should be within 0.6V. 3. When the test machine, for the safety, the lower voltage experiment (such as ± 25V) should be used, the signal is not added, and the output terminal is measured, and the output terminal is measured, and should be within 20 mV. 4. The final stage bias circuit is formed from R8, R9, R10, D1. This bias makes the output tube VT1, VT2 are not closed at operation, so the static current can be smaller (about 5 mA). 5. The power tube should be strictly paired (3%) and use genuine. The output-side resistor R14 employs a 5W-free, inductor L, the inductance L. wire is formed on the R14 10 turns in R14. TDA7294 uses a 60mm × 85mm × 20mm twelve tank, and the output is used to use professional heat sink. There are high currents on the printed board to be rolled, which is beneficial to the transparency and strength of the play. Figure 2 Power amplifier PCB board driven by TDA7294

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