Input Processing and Auxiliary Subsystems
This chapter deals with input processing functions such as gain control and filtering, and other power amplifier features that are not part of the signal path, but perform ancillary functions such as level indication or control of on/standby switching.
If balanced inputs with high CMRR are used, they should deal effectively with the humming and buzzing ground currents that result from the existence of ground loops. However, in an emergency it may be useful to have a means of lifting the ground without creating a shock hazard. It has to be said that it is often not very effective, and is a last resort when the audience is starting the slow handclap.
The typical ground-lift ...