Here is a thread that may help you better understand DC on the mains.
Just bought the Audiolab DC blocker. I have two dedicated AC outlets feeding my system. Since I expected there to be possibly some DC seeping through and the EMF filtering, it was worth a try at $150. First off it created what sounded like a cleaner sound throughout. Crisp revealing but what little 'hum' that was residual in my system was also much clearer. At first I reasoned the enhanced clarity was worth the trade off but then I noticed something else troubling. The entire presentation had lost something. After giving the unit a week to break in (although it was a demo unit and hence should have had some miles on it) I pulled it out and listened again. Without overtly realizing it, the presentation had lost the warmth, organic, musical, 3-D quality to it. WOW, my system's magic was back. I'm a bit unsure what actual effect the Blocker had. Seemingly clearer but flat OR pinched I might say. And that extra 'hum' was gone receding into the faint background as I am OCD about the smallest trace of system sound of any kind. Unit has been returned for full credit. Lesson learned. Same result with "power conditioner" by Furman.
@allears4u it is redemanded to use on source equipment such as DAC, Phone Pre, Streamers/servers. Not recommend for amplification. I bought a couple of these for my Daughters system as they live in a condo and worked quite nicely cleaned here system up, used on Analog and Digital sources.
Good tip! I now wish id tried it on my other components. What caught my attention was this line in Audio Advisors description of the DC Blocker.....Quiets "modern high flux toroidal transformers" . Well, thought I, I have two of those humming along on top of my tube amp which always could be a little quieter. So....live and learn (and loose $15 for return shipping!)