The simplest structure OCL power amplifier

The circuit structure is very simple, but the performance is very good. There can be almost no less components used in the circuit, which not only reduces
production costs, but also makes debugging very simple. Its principle is shown in Figure 2-5.
    VTl and VT2 use a differential input stage composed of an extension tube, which is
different from the structure of most input stages that use NPN tubes. The advantages of using napkin tubes are that the tubes are easier to match and have better consistency, and the operating noise is lower.
    VT3 serves as both a voltage amplification stage and an output drive stage, so it is required that this stage should have a higher voltage gain
in order to provide sufficient drive power for the output stage.
    VT4~VT7 form a composite fully complementary push-pull output stage, vT5 and Vr7 form a complementary push-pull PNP pole composite tube , and
VT4 and VT6 form an NPN pole composite tube. Both sets of composite tubes are combined in the simplest structural manner,
reducing circuit components and eliminating the need for adjustments. However, the penetration current requirements of VT4 and VL in the composite tube
are extremely small to ensure the stability of the circuit operation.