This morning I did some test connecting my shure SM57 microphone to pedalSHIELD. The output level of mics is pretty low, so first of all you have to adjust the RV1 trimmer to give maximum input gain (top-clockwise). It will provide a gain around 26dB (20 times).

The setup was:
external sound ---> Shure SM57 ---> pedalSHIELD ---> Laptop line-in



I recorded a short demo in SoundCloud with Audacity software in my laptop:

For the first "voice part" I use the echo effect in pedalSHIELD. For the second "guitar part" I put the mic in fron of my amp and I recorded using the clean effect (distortion is created by the amp).