Hello there. Thanks for stopping in. I've hit a wall. I have been using a Digitech RP355 for 7+ years. Then one day I hooked up and as soon as my guitar was plugged into the board, my speaker started creating ridiculous distortion, and not the good kind. I wasn't even playing and it was just humming. Crazy loud. Crazy ugly. Couldn't find any reason why. I switched cables, plugged directly into the speaker from my guitars (no distortion, so not my guitar, cables, or speaker), and went into the board and out using the headphone jack on the pedalboard and was getting the same distorted sound. So I said pedalboard; I thought it was a messed up quarter inch input on the 355. Got a new one, the RP360XP. Got it ready to go, and then THE DISTORTION WAS STILL THERE. I plugged my phone into the Aux jack on the board and went into the speaker, and it played the music fine.
The distortion just seems to be whenever my instruments are plugged into the board and then into the speaker. The speaker plays my instruments fine when they are DI'd in, and the board can play MP3's from my phone through the speaker fine..
Any ideas on what my problem is..?

Hit me with requested details to help you think more if that's what you need. I'm gonna be messing with this all day.
I really appreciate anything you can throw my way to try.
Scratch this. Apparently the outlet I was using has a grounding problem and it literally started last week at some point. Another outlet in my place works just fine. So just a messed up circuit to make me frustrated. I'll just play in the kitchen from now on.