you can do many things... but usually only the ground connection is utilized when we speak about grounding boxes.... either a AC plug ground, RCA,XLR, COAX, AES, BNC etc ... i guess the most problematic thing would be the AC plug here...
in the case of these tourmaline rca caps i got the idea from a german diy forum, they extend the plus pole of the rca but basicly dont connect it... the theory around is that this is only thing that actually enables a electromagnet field to activate the tourmaline
listen expression is difficult, imo also the ones without signal do already a great job (but the ones with signal utilize "do more", but imo the effect is not only positive, just more audible) and preferably i dont wanna build a theoretical capacitor that can actually alter signals
and with these rca caps you basicly dont build anything more than a fancy rca cap (which i guess actually shield the signal pin, if you build the cap right), which still seem to alter the sound positively
IMO its worth a shot if you are curious, thats why i write about it... no one has to buy "snake oil" rca caps for 200$ if you understand the principcles and do a bit of DIY, unfortunaly the industry seems to like to utilize these "secrets" and also keep them for themself because things (if i look at furutech Nano Crystal Formular) are that confuse no matter where you look...