If one was looking for an audio amplifier of high quality, with very low distortion, which one of these two options would be better?
- Large loop gain (i.e. \$af\$) but small open loop bandwidth
- Small loop gain but large open loop bandwidth
I think that the first option would be the best one, because a large loop gain would mean that the bandwidth of the final circuit (namely, the closed loop bandwidth) would be increased by a factor of \$(1+af)\$, so the bandwidth would not be a problem. But also, distortion would decrease by the same factor, so, as I see it, the first option guarantees a large bandwidth and a decrease in distortion, while the second one only offers a large bandwidth.
However, this is a very general reasoning. I don't really know where that decrease in distortion comes from: does it depend on the position of the open loop poles? Does it depend on anything as well as on the loop gain?
So the specific question would be: which one of the two options would you choose for a very low distortion audio amplifier, and why?