Typical OCL power amplifier circuit

The working principle of the OCL circuit has been introduced in detail before. Here we might as well give a systematic and brief
hint to facilitate the next design calculation.
    We know that the OCL power amplifier circuit uses a multi-stage direct coupling circuit structure, and its DC operating point
is established as follows:
    starting from the output stage, a composite tube quasi-complementary push-pull output circuit is composed of VT~VTio. In order to avoid
crossover distortion of the output signal, the output circuit operates in Category A and B, that is, VT7~VTio requires a certain static operating current
, concave~Icl0. 'The flow direction is like this: in the upper part, the power supply is v+1, C7, and the round speaker (RL) is on the ground; in the lower
part, the ground is on the speaker (RL)-IC8, fCl0, Vo, and f. =ICs, when f09=IC10, the voltage between point D and ground is
ov, which is required by the circuit.
    Adjusting RPi or R/ can adjust the voltage at point D to port
    J of ov. The size of I is determined by the voltage drop of I on Rio; Iclo is determined by the voltage drop of Ic8 on Rl2.