Commercial solid state amplifiers with no loop feedback around the output stage

I guess the triple driver wound raise the OPS input voltage to something a bit closer to a FET OPS making the error correction easier.

I tried using a bipolar OPS with err correction (sim only) about 10 yrs ago using a low voltage WB video opamp driven off supplies bootstrapped to the output rail. Seemed to reduce distortion significantly but I took it no further and did not check stability.