Let me preface the below video clip link by writing that the noise you hear when the video starts is already the noise I am currently troubleshooting.

A little bit of backstory first: I use this PC as my music production computer and am very happy with it - however, the noise I am experiencing seems to come when I connect my midi interface (which is connected via USB 3) to audio equipment.

I have tried different MIDI cables and audio cables and different wall sockets.

I would be VERY grateful if you could watch the whole video before commenting as I am really very serious about trying to solve this so the more info you have the better. Thank you for your time and help!

Here's the video:

https://www.youtube.com/watch?v=-Gflbq1KZHk

Is all equipment grounded?
You could try an midi cable without the shield connected on one side (groundloop).

Thanks for your reply - yes, all my equipment is grounded and high end - have you tried this MIDI cable trick? Did it work for you?

It's not a MIDI cable trick but something you can do to prevent ground loops, also on audio cables.

For me this occurred via two sources - synths that had USB midi outputs which were connected to my PC (pretty sure it was mainly synths with external power wall warts, maybe wall warts with only two prongs I can’t remember). The noise could be heard via that particular synth’s audio output via 1/4”. Moving the mouse made it worse.

The second was a backlit USB typing keyboard that had LCD lights. Cycling the lights cycled the digital noise.

No idea if your setup has this currently (the Strymon?) but if so try removing some/all of that.