So, I opened a ticket with Line 6, and, I have to say, pretty unhappy with them,so far.
I did discover that there is an issue with the digital cable, the AES or Link cable they call it, in that when I unplug it from the Helix LT the issue seems to mitigate to a certain degree. Actually quite a bit. But it still has a weird mid-range boost that sounds like it's around 1 to 3 K, but definitely improved when I unhook the cable. Thinking it was the digital cable, I ordered another one, received it plugged it in, and... Same issue
I'm convinced there's something wrong with the power cab. I responded to the ticket I have open, and I'm waiting to hear back from Line 6. Unfortunately I bought this cabinet either is a B stock or used I can't remember because it was a year or two ago. So I probably have no options in regards to warranty. This cabinet has never been gigged, and never been out of my studio, and doesn't get used that much. This issue just all of a sudden appeared, not like happened after the cabinet was dropped or something of that nature. Pretty disappointed in this product at this point. I really loved it when I first got it it, sounded awesome, but now I can't even stand to listen to it when I plug the Helix LT into it. May end up selling this stuff and going in a different direction. Not happy with line 6 customer support either.