Abstract: A conference-type audio amplifier system has a plurality of voice-controlled microphones which produce individual output signals. Each microphone has an analog switch for turning the microphone on or off in response to its control signal relative to a reference threshold. Features of the system include: a number of microphones may be on simultaneously, and the remaining microphones (off) have their thresholds reduced by the on microphones; all the on microphones are kept on during speaker pause; simultaneous sound to multiple microphones (such as applause) causes no turn-on of any microphones and can reset the entire system, and one or more microphones switched to manual-control cause all the microphones switched to non-manual to be off.