How to remove noise from DC line?

I decided to remove the 5v regulator that powers the DAC chip on my squeezebox and use the 5v line off my ELPAC power supply to power the sb and the DAC at the same time. When I did this, I have a bad humming noise from the speakers, but the sound has improved. What do I do to eliminate this problem? Should I use a DC line filter? Thanks for your time in this matter.