Mike,
I grew up in the jewelry business and for many summers worked in my Dad’s plant where I did various jobs, including a lot of rhodium plating. My understand of why rhodium is used over silver and white gold, is due to its non-corrosive properties which makes it highly impervious to oxidation. However, in audio, I’m not sure I understand the benefits as easily. If we assume that one principle for audio signal transfer is to minimize resistance so as to enhance signal conductivity, everybody knows that silver is the king of the metals in this regard. However, it’s susceptibility to oxidation is often considered a detriment to its use in audio wires. Copper is a very good conductor and aside from being a very malleable metal, is often coated to protect it from oxidation (copper oxide is a horrible conductor). However, when plated, it is a quite acceptable material for contact surfaces. Gold is also a superb conductor and offers outstanding oxidation resistance.
Rhodium on the other hand is a metal whose rationale in audio escapes me. Rhodium is a precious metal from the platinum family. It is hard, acid-resistant, and has a very high melting point (1964°C). Compared to other platinum metals, it is a very good conductor, but still only half as good as gold and just one third as good as silver. Therefore, it is misplaced as a coating in a domestic environment. Its sound characteristics are often described as harsh and analytic. It does however have its justification in industrial environments with high temperatures, for instance near blast furnaces, where it reliably does its job at temperatures where gold would already start to melt (which it does at 1064°C).
Despite these traits, I too thought that if companies like Furutech thought enough of rhodium to start plating their receptacles and contacts with it (and charge more for it!) then what the hell, I might as well try them. Any audiophile knows that data is data but the correlation with sonics often has nothing to do with technical performance, electrical or otherwise. So I did. When I built my home 3 years ago, I inserted all rhodium GTX-D Rhodium outlets in the music room. As many know, the room and the gear was virtually identical to my last home in Dallas which had good old copper plated hospital grade outlets, yet something just wasn’t well, “right”. It wasn’t until after someone I respect clued me in that my problem might be the rhodium plated outlets, that I started exploring that hypothesis. My first swap was on the amp outlets (because they were the easiest to install) and I was stunned at the effect of switching to the Furutech gold version of the same. The other outlets for the front end followed despite requiring the contortions worthy of Houdini to change them, but in the end, I have not looked back. I agree with you, it’s all about tuning and that is certainly system specific. Since these are relatively inexpensive changes that can have considerable effect, I would encourage anyone who wants to explore this to go slow and make one or two outlet changes first to see if one of these outlet materials is your particular cup of tea.
Marty
