Hypotheses on audible differences we don't know how to measure

Let’s have a concentrated discussion on anything that people generally tend to notice as audible differences but that has no established scientific basis as of yet (relating to signal transmission). I think this will be mainly about materials… Whatever comes to your mind, share hypotheses and of course theory if there is any.

I’ll start: What’s really interesting to me is that different platings on same material base metal on mains plugs can make an audible difference. Gold, rhodium, silver, over copper, or what have you. The differences heard by ear are numerously reported.
The goal is to transmit 50 / 60 Hz AC with lowest impedance, seemingly the simplest task in the whole chain… and here’s just the connectors! We don’t want oxidation, that’s easy, have any plating that doesn’t corrode. The plating is very thin… Now what possible factors could be at play that could possibly impact the clean power transfer characteristics? Let’s assume the connection is mechanically “optimal” on the macro scale.

What we know is that rhodium is extremely hard, so if we have rhodium against rhodium, even at micro level the connectivity won’t budge, not even with repeated un/plugging.
Gold by contrast is very soft and it won’t retain a smooth surface on micro scale for long. There’s gonna be gold powder. However - this softness could be a possible benefit if we have a gold-to-gold contact, because gold atoms’ adherence is such that it practically welds to itself on the micro scale (“welds”, a strong word, but anyway…). What I’m getting at is that a gold-to-gold interface could have essentially less “air” inbetween, compared to rhodium. A mechanical inferiority lending itself to better micro-scale contact resistance, get it?
Such micro (or nano?) scale variations in contact resistance surely aren’t measured easily and I don’t think anyone will bother since it’s an unknown to this day. This is my hypothesis - gotta try to make up something that might have something to it because as stated, the ears of people are picking up some difference, as strange as it is.
And to add - I believe in so-called system synergy being tied to the use of as much similar conductor as possible, yes, down to the crystal grains. Having dissimilarity here just strikes me as doing possible harm, I mean, mixing metals can sound better with all variables involved but at the cost of an integrity whose workings aren’t so clear yet.

Please go crazy. This is NOT a thread for established engineering principles!

  • you can’t talk science then not insist on at least a scientific validation of audibly not anecdotal

  • there is little to no evidence the goal is the lowest impedance on AC. Arguably that goal is flawed. It helps on ground connections and is bad for everything else

  • gold is used because not only does it not tarnish but because it is soft and that increases the contact area. This is not new or unknown.

  • rhodium is not used for connectors anywhere except audio. That should tell you something. A hard poor conducting surface does not a good connection make.


Didn’t understand. What did you mean? Of course we want the lowest possible impedance for mains transmission, could you elaborate how resistivity is of any benefit here?

Rhodium does make a good contact, Galen had some info on this - I was wrong about it being hard, no, it’s robust, not hard. It, too, “pushes the air out” from the contact due to softness and the contact resistance is thus low. But gold is even softer, so soft that it has the disadvantage of wearing off. But might be it’s worth it over rhodium if it’s not plugged and unplugged all the time.

Most connectors are NOT gold plated (because of cost) they are gold alloy flashed. (very little, if any, actual gold content) Rhodium is still a full 50% more conductive than the brass it will likely be plated on.