I don't think shorting plugs (or caps) will have any effect on the effects of cross talk in your pre-amp. Now if your tuner, for example, is off and you are hearing music from a radio station, you might get some help from shorting plugs. Might. I have used shorting plugs in several of my units and have had minimal, if any, beneficial results. I'm not techie enuf to even begin to understand the benefits of cap's although I've read the product claims.
Don't think there is much you can do except turn off sources you are not using.
FWIW.
Don't think there is much you can do except turn off sources you are not using.
FWIW.