This is far the cheapest way to improve your audio system and better than even switching power cords and cables.
Everything improves. Tip use two at the male end of your cd player than one at the IEC end. Zero noise, more body and micro details.
On non digital gear it is case by case. I choose to go without, but with my old audience power cords they sound much improved with one cooper union on each of the male plug ends.
This is by far one of the best bang for the buck addition I have ever used in my system.
Everyone who as tried it have said about the same thing.
You blocking noise from the outside world, now to add to that get some rca shorting plugs (not Cardas caps) use then on all unused inputs, less noise again and this is also cheap.
If you run balanced like me do not use them on the RCA jacks on the same input as the XLR.