I've been using various 10XX series modules for a while now and was wondering in anyone knows the correct setting of the switch on the back of the module. I've always just went with whatever it was already set to, until I starting hearing about a "correct" setting for a particular mic. I recently spoke to someone knowledgable, and they said if you are using newer microphones, set it to HI. I did this with a Royer R-121 , and got a considerable amount of noise, so I switched it back to LO. I've tried other mics and A/B'd the differences between the two settings, and I can't seem to really hear a difference. I used an AKG "The Tube" mic the other day with the module set on HI and got a nasty ground loop. When I switched it to LO, it went away. This was a 1073 module mounted in a Mercenary two-space chassis. The same module mounted in the console it came in does not produce the ground loop under the same conditions. What gives?