50W Class A and B power amplifier

Enthusiasts all hope to make a high-quality power amplifier, but the excellent circuits published in most publications are often too complicated
to start with. 6 This article introduces a pure power amplifier circuit with Class A and B output. The circuit is simple and the sound quality is satisfactory. Those who are interested
may wish to try the cardiac
    circuit as shown in Figure 4-3. VTI ~ VT4 form a first- and second-level differential amplification, VT6 ~ VT7 form a power output tube,
VT8VT9 is the driving circuit o VDl - VD3VT5 provides bias voltage for VT6 ~ VT9. The gain of the circuit
is controlled by R6 and R7 to about 30 times. The whole circuit is concise and clear at a glance.
    The adjustment of this machine is very simple: adjust RP1 so that the midpoint potential is ov; adjust RP2 so that the voltage at both ends of R13 is about 0.1V. It can be put into use after repeated adjustments several times.