running springs looks indeed interesting from an off the shelf perspective.
welbornes labs has interesting filters as well.
Guys, just so you know, I had zero, I mean zilch electronics knowledge about a year ago, then I undertook building my own power conditioner. That was the spring board for my DIY journey.
If you guys want to start a seperate thread in the lab I'd be more than willing to share with you info on what I did from another newbies perspective. I am sure we can get DVV, Occam, JohnR and other highly informed individuals to chime in as well. The balls in your court.
You can make it as little or as big a project as you want, but it really is quite simple to do, honestly, but you do have to be cautious and smart as you are working with mains voltage! Nothing to fear per se but don't work on it with the power plugged in, etc.