I'm using a Long dog audio one inline to my power conditioner. it makes a positive effect in my opinion in my system but it does limit my power cord to 12 gauge.
my issue is a fish tank with variable DC pumps and variable LED lights.
one day I'm going to try blocking the DC at source (other side of the room)
Then taking it out of the system, I get no hum on my transformers without but I find the tone sweeter with it.