I want to connect three microphones to an IC which will be giving out a single output when only one microphone is on. When two or all three microphones are on, the output should be zero. This output will then be fed to the main amplifier. Thanks in advance.

Josh, December 2015

Use a 4 way selector switch - double pole or single pole - single will do.

Connect the output to the IC as required
Connect the Microphones as follows

Position 1 - no microphone connected to the IC
Position 2 - Microphone 1 connected to the IC
Position 3 - Microphone 2 connected to the IC
Position 4 - Microphone 3 connected to the IC

This is a mechanical arrangement - if you wish to do it electronically there needs to be some way of deciding which microphones are "on" - microphones are always on - it's just that sometimes they're just not connected.

Good Luck..., December 2015