My 2 cents. Silver is the best metal conductor. Some relays and large contactors use silver cadmium alloy. Solder is an alloy. Soldering causes a bond with the different metals. Just having different metals touch each other is not a chemical bond. Gold is actually quite poor. In ANY case you should never mix metals. Whatever you have SHOULD all be the same. Different metals can attack each other. It is not the oxidation but the reaction that degrades the signal. Many computers fail within a year because they mixed tin and gold connections on the memory modules! A diamond shining in pitch (complete) dark? What are you smoking?! There had to be some tiny amount of light from somewhere you could not see directly. As far as computers using coax, the digital signal also has parity and error correcting which is not in audio that I am aware of. Coax can possibly have interference but optical? Cosmic rays maybe? Coax not carrying an electrical signal?? Hang an O-Scope on it and take a look! That's not grape jelly in there! In any case, if there is enough interference/signal loss (from any cause) to cause the digital 1's to be too low or the 0's to be too high then you have a serious problem!