Answer
(Fatwa: 1656/D=370/K=1431)
(1) The experts have reached a conclusion after research that voice of microphone is the exact voice of speaker. It is not an echo. Hence, it is right to offer salah behind an imam who is leading the salah by mike without any dislike. However, it is better not to use a mike in a place where there is not huge gathering and mike is not necessary seeing the khushu khuzu, because sometime it does not work properly and causes interruption in salah.
(2) It is lawful to use it for Azan. I have written Islamic ruling. Those who talk about unacceptance of salah if they are not Alim then their words are unacceptable. And if they are Ulema, request to write their stand in detail with proof and attach their writing along with your istifta and send it back to us.
Allah (Subhana Wa Ta’ala) knows Best
Darul Ifta,
Darul Uloom Deoband