Linear Power supplies for DACs...?

If not, buy a new DAC yours must be pretty old and junk since even cheap ones now have pretty good filters. In others words it's  placebo. Good modern DACs  work really well with whatever power supply they came with.

The noise issue with switching supplies is primarily common-mode. Fitting a common-mode filter on the DC feed to a DAC would be sub-optimal, its best position is on the mains side. Anyone got example DACs with CM filters on their power inputs?

Just go near any SMP with a portable AM radio tuned down low in the dial somewhere 5-8 hundred kilohertz where it’s quite turn up the volume make sure it’s not auto muting and see the noise it put out when you wave it around an SMP.
And this is radiated RF, it penetrates everything bar a Faraday cage, then also add what’s going back through the mains wiring of the house.
Many amp manufactures that use SMP's in their better higher end models they have linear supplies in them, think why??

Cheers George

Don't neglect the DC cable. It's just as important. The Cerious Matrix DC cable provided a surprising boost in sound quality.