Balanced is always better for reducing RF or ground noise, but it sounds like you have a ground loop based on where you have your console and MOTU gear plugged in. Are you using any power conditioning? Try lifting the ground on the MOTU (temporarily) to see if it goes away. Best to get both items on the same circuit, preferrably a dedicated one with isolated ground. Good luck with it.

be sure to check your signal cable routing. Make sure all signal cables are routed away from power. Watch out for those roach box power supplies. They radiate 60 hz like they were designed for it. If any signal cord is within a foot of one of those I would move it.

randy

Another trick is that if you can't effectively seperate signal lines from power lines, tape them to the floor at 90 degrees to each other, a variation of the "hum dance" that anyone who plays a Fender is intimately familiar with (myself included).