Wall socket to mains purifier/filter/conditioner use a dc blocker incorporated into a mains lead like the isotek syncro (as an example only), I have tried mountains of filters/regenearators/conditioners and the best solution was the dc blocker and an isotek aquarius (for me anyway), the PF30 I had was good but the aquarius tipped it when I wired schuko plugs to all my power cords and used an aquarius with schuko sockets, getting rid of all the fuses in the power cords works wonders.