someone can help me to analyze this circuit?

[paulopca]

Hi everyone!

Someone can help me to analyze this circuit? It is a circuit of a power amplifier.
This amplifier has already been assembled and I know that it works.
Q13, Q15, D6, D7, R18 and R21 form two voltage stabilizers feeding U1.
Q12, Q14, D5, D8, R16, R17, R19 and R20 form two current sources.
Q11, R14, R15, R16 form a vbe multiplier.
Q1, Q2, D1, D2, D3, D4, C1, C2, R1, R2, R3, R4 form a VI limiter.
Q3 and Q7 are predrivers.
Q4, Q5, Q6, Q8, Q9 and Q10 are output drivers.(2SC5200 and 2SA1943)
U1 (tl071) is the input stage.
All right so far?
I don't understand how the op amp drivers the output stage and how the local feedback of the op amp works and how the global feedback (feedback between output and the op amp) works.
I thought the voltage amplifier was the op amp, but the signal level at pin 6 (output) is much smaller than the signal level that drivers the predrivers.
The VI limiter it's ok? If not, someone can help me to correct? The source is +40V and -40V and the load is 4ohms.
What is the maximum power that this circuit can achieve with a load of 4ohms and what source?
This circuit can work with a load of 2ohms? Under what conditions?
I'll be very grateful to anyone who can help me.

 

[ChrisP58]

The output of the op-amp really doesn't drive anything except the load resistor R24. But, to do that, the op-amp has to draw current from Q12 and Q13. It is the base current controlling the collector curent of Q12 that ultimately drives the output.

Q14 and Q15 does the same for the negative side of the operation.