Self on Audio, 3rd Edition

Chapter 24Distortion in power amplifiers

Part III: the voltage-amplifier stage (Electronics World, October 1993)

Unlike the input stage, the Voltage Amplifier Stage or VAS does have to handle big signals as its output swing is slightly larger than that of the output stage, and various distortion mechanisms that are of no importance in the input stage become very significant. The main reason why this stage works as well as it does is that it normally has a Miller dominant-pole capacitor connected between its input and output. As the frequency rises, this component smoothly transfers the global negative feedback right round the amplifier to a small stable loop around the VAS, providing it with a high level of local feedback and reducing its distortion. ...