30W power amplifier circuit

This circuit is a power amplifier circuit that uses field effect transistors as output . The operational amplifier NE5532 is powered by
a ±15V power supply, and its output is amplified by a first-level voltage to drive the FET output stage. The voltage of the bias circuit
    of the output stage is taken from the ±15V input to the pre-stage, and is supplied to the bias circuit after being stabilized by VT3 and VT4. The positive and negative voltage regulator tubes VT3 and VT4 use two LEDs as voltage references. The LEDs not only have good voltage characteristics, but can also be used as an indication of the working status of the circuit. Using this power supply circuit not only becomes a constant voltage bias with excellent performance circuit , and it can be used as a constant current source load of the pre-stage to increase the gain of the output stage.     Vn and VTz form a push-pull output push stage, which is also a set of common emitter circuits with voltage amplification capabilities. Vr7 and VTs form the overload protection circuit of the output tube.     ICIb (lf/ NE5532 ) and so on form a zero-point servo circuit. R23.C4 and ‰ form a negative feedback circuit.     The output stage vMOS tube uses 2SJ115 and 2SK405. 0 can also use IRF9130 and IRF130. The parameters are: transconductance is 4, withstand voltage loOvPCM=75W, Iau=9A.     During debugging, just measure the voltage drop on the 0.22fl resistor to be 40~50mV.