Stock ADA MP-1's are noisy. In your Youtube video, nothing strikes me as odd, other than the buzz when the audio interface is used. (I concur that it is probably a ground loop.)

I haven't done anything to my MP-1 in a bunch of years now; just enjoying it daily!

When I ripped out all the audio-passing op-amps and replaced them with better ones, it really cleaned up. I couldn't believe I could just put down the guitar on a stand, mute the strings and walk away.

Those ADA people created a lot of future work for hobbyists by creating a great design, and then stuffing it with some crappy components. But for some of us it is worth it.

On 2018-10-10 06:03, Pilau Tigered wrote:

Hello Kaz and the ADA MP-1 mailing list!
I have recently acquired a used ADA MP-1. The unit is rather noisy and it has a faulty front input plug. These issue led to hours of research and discovery, including finding out about this mailing list and Mr. Kylheku (among other leading figures in the mp1 technical community)
** I'd love it if someone could help me debug and locate the source of the issue **
I have also put together a list of information and mods/upgrades/refurbishing instructions and other technical resources for the ADA MP-1:, feel free to check it out