I'm not sure how they could change the sound. They should be sonically inert.
They should be sonically inert but the difference is very obvious to my ears, I tried it with and without numerous times. Sometimes the difference is greater than changing tubes, especially in regards to what happens to the soundstage and imaging. Each tube reacts differently to the socket savers as well, some more favorably than others. But generally the sound becomes a little brighter overall and more spacious with the socket savers.