[Walkerdiv]

Hello,
I am trying to design a pre-amp for a range of elecrtret and dynamic microphones.

See attachment.

Some headset dynamic mic has 5 ohm impedance while others have 150. Is it input impedance of 20K looking into the op amp circuit too high or is it ok?

Beyond, I have 2 more stages. One with minus 90 to plus 30 dB vol control stage and another 30 dB fixed stage to allow me a range of headsets

Thanks,
Walker