I understand why there is distortion if there is no opamp there, but not when there is an opamp with the output is connected back to inverting input of the opamp. The output would always equal to the input * gain no matter if the transistors off when input is -0.7 -- +0.7V? Is this correct?
Edit: I did a Fourier analysis at the output with 10khz sine wave, and the THD is only 1.3%.