It seems my room is picking up gnarly EMI interference from somewhere. I don't really get any low end hum from it, it's more like a high pitched whine. When I turn the volume up on the guitar it picks up crazy EMI, way more then the other units. I do happen to have top and bottom covers off and am playing it out of the rack, would this be why?
I definitely don't think it is a ground loop issue though. I recall that is more of a low end 60hz sound. This is just a crazy amount of EMI with a high pitched whine. Unfortunately it happens with all of my guitars, they all have humbuckers too so it's pretty confusing.
Looking at a frequency analyzer, the whine is at 3.5k, with harmonics at 2k, 1k, and a little activity at 125. The guitar feedbacks at those frequencies when I turn the volume up and let it ring out. Testing with my little pre amp pedal, it does not have the same high pitched whine, but definitely has EMI interference, although it is so much worse through the MP1. Plugging back the MP1, you instantly notice the whine and way more EMI. The whine honestly sounds like a b string harmonic at the 5th fret. When I unplug the guitar from the MP1 with the guitar volume off, at the MP1 input, the whine gets quieter, and gets a little louder when I plug in. I wonder if it's the MIDI clock or something?
Anyways, thank you for your help. It's a little difficult to describe, and the EMI seems to be worse at different times of the day. Just a very frustrating experience! It seems my room is located in EMI hell haha. Trying out with my other MP1s, it does not make the same high pitched whine, so this one is unique in that regard, as well in picking up so much EMI. The visible difference I have seen with this one is it is a later version with no top switch, and the instrument input is tied together both front and back. I have attached a picture showing the jack. I've also noticed the transformer is a little different then my other 2. Thanks again!