
I use an H11F1   FET optoisolater to switch microphone level signals.
There is no click, since I put a .1uF cap across the LED.  Distortion
measurement are very low with mic level, and they went up to 0.03% at a
+ 14 dB line level.  All I did was put the FET in series with one leg
of the balanced line.  No hums, pops, just audio jumping out of silence.
The FET runs about 100 million ohms with the LED dark and drops to 150-200
ohms with it on.