Re: Noise in Power Supplies
most hum is going to be 50/60 hz . You can purchase a noise supressor to plug the PS into and helps eliminate a lot of the hum.
Make sure you have a good ground. Some PS's only have two conductor power cords with no ground and can cause problems with excess noise.
Also, check the output cords from the PS in some cases a nick in the wiring insulation can cause a pick up of outside noise. It's rare but has happened to me.
Some power supplies don't ground the transformer. You might check that as well.