Pure Class B CL power amplifier circuit

In the circuit, the diodes VDi and VIBah are used to stabilize the base bias of VTi and VT2, so that
when the power supply voltage changes within a certain range, VTi and VT2 have a more stable static operating point. At the same time, if there is a temperature change
, since the temperature change of the diode PN junction is in the same direction as the triode PN junction, it can compensate and protect the temperature
stability of the circuit .     C1, R7 and C2 form the filter network of the input stage bias circuit to reduce the AC interference sound of the input circuit. Experiments have shown that the effect is very different whether the circuit is connected to people or not.     VTs~VT8 form a composite quasi-complementary push-pull output stage, which has been adjusted to Jo=/C4 in static state. Therefore, when there is no signal , the output tubes are in a cut-off state, that is, a pure Class B working state. When there is a signal, the outputs of VT3 and VT4 are added to the bases of VTs and VT6 in the form of current , thus avoiding crossover distortion caused by the transistor input dead zone voltage .     Circuit debugging: Connect one of the two multimeters to the positive power supply, and connect the other between the output terminal and the speaker. Rotate RPi to the ground terminal and connect) 2. Rotate RP3 to the maximum resistance terminal and turn on the power supply. Adjust RP2 and RP3t at the same time and keep the current reading of the meter in the output circuit at 0 during the adjustment process . When the current of the meter in the power supply is adjusted to 2-2_5mA, it is enough