70W integrated power amplifier

From a Hi-Fi perspective , as an operational amplifier for voltage amplification and power promotion
in a combined power amplifier , its output amplitude should not exceed sv ( when the operational amplifier power supply is ±15v), so the power output after the operational amplifier The stage not only requires a large current gain, but also requires a certain voltage amplification capability. The voltage amplification factor of the output stage of this circuit is set to 7 times. In this way, the output amplitude is 5v×7-'5V, reaching the full amplitude. And make the output power 70W. If     the wiring is correct and the speaker is not connected to anyone, if the output voltage is measured to be zero, it means the circuit is basically normal. Then adjust R9 and Rl0 so that the final current is 5mA ~ 20mA (when adjusting, start from Zero gradually increases its resistance value, and cannot be opened. After adjustment, replace it with two fixed resistors of the same equal value), and then it can be put into normal use.