Hi,
Audio amplifier normally have three stages:
1) Input stage Q1, Q2 and Q3
This is a long-tailed pair with a current source, Q1, D8, D9 in the emitter.
2) Voltage amplifier stage VAS
This is Q6, Q16 and Q17
3) Current amplifier stage
Q10, Q12, Q14 and Q15
There are two Darlington emitter followers, voltage gain=1
Q8 and Q9 are for overcurrent protection
Q7 is vbe multiplier to compensate for vbe in the output transistor stage.
In the VAS, D10, R11, R13 Q6 is a current mirror. it would look more like a current mirror if D10 was replaced with a diode connected transistor.
Q16 and Q17 is another differential amplifier
The current mirror load gives higher gain than if resistors were used.
Regards,
Jay_Diddy_B