Class A and B DC power amplifier circuit

The whole circuit consists of a dual differential input stage, voltage amplification stage, bias circuit and power output
circuit.
    The input stage consists of an input interface and a dual differential fully complementary input circuit. There are three input interfaces: Interface 1-2 is suitable for
connecting with a preamplifier with balanced output with volume control. Interface
2-3 is suitable for connecting with a preamplifier with unbalanced output without volume control . VTi ~ VT4 form a differential input circuit, RPl and RPz are balance adjustment potentiometers.
    VTs~VT8 form a dual differential complementary voltage amplifier stage.
    VT17 and VI)l are used to form the output stage bias circuit, and VI is a temperature compensation diode. The output impedance conversion stage is composed of VTg and vTio
, and an emitter output device is used to improve its load capacity
    . Ⅵ¨~VT16 form three pairs of parallel complementary push-pull power output stages, and the quiescent current of each tube is adjusted to 380rnA.
    Ma and Ra form a negative feedback loop. The closed-loop gain of the whole machine is determined by Rg/R8. About 31dBocz and C4 are phase compensation
capacitors to eliminate self-excitation.