What's the best plating material for interconnects plugs ?

If the base metal is garbage, it doesn't matter what exotic metal is plated on it. Throw in plastic for the insulating/molding parts and the problem is compounded even worse. One gets what one buys...

@williewonka +1
Great advice given.

My only add would be to mention a couple of brand names such as Vampire Wire that used direct gold plating over copper and their upper Xhadow line that used direct silver plating over copper.  Unfortunately, Sound Connections (the parent company of Vampire) recently closed their doors and Partxconnexion purchased the remaining stock and the rights.  
ETI Research also has some nice designs.

@williewonka
I was under the impression that silver plating directly on copper is not a good idea. Copper readily diffuses into silver and forms a copper/silver eutectic layer which negatively affects adhesion and electrical conductivity. Typically a copper surface is pretreated or a barrier/adhesion layer is deposited before the plating of silver.

Any amount of visible tarnish will reduce the surface conductivity of silver. A micron is a lot of tarnish. A micron of tarnish can reduce the surface conductivity of silver by as much as a factor of 1000.

@ljgerens - I do not know the science that goes into plating, but these guys seem to now about the Silver plating onto copper in the field of electronics
Silver Plating of Copper or Copper Alloys - Advanced Plating Technologies

They appear to confirm what you have said - almost to the letter

But they also state that for "pure copper"

The copper can then receive a nickel underplate (if specified) followed by a silver strike and finally the silver plating. The silver strike layer is very important to achieve an adherent silver layer and avoid silver immersion that would result if the copper was immediately silver plated without a strike.

So the nickel underplate seems to be optional and the Silver strike takes care of adherence

But on the more practical side of things - I trust my ears and after many years of listening to different materials on a variety of connectors I find the following to provide exceptional performance

1. KLE Innovations Absolute Harmony Silver plated RCA plugs
2. KLE Innovations Harmony Silver plated Banana
3. Sonar Quest Silver plated Copper Mains and IEC connectors

Keith Louie Eichman has spent a lifetime (close to 40 years) making connectors and cables and it seems he has an affinity for silver plated copper and based on the excellent performance of his products - he must be doing something right.

And I am yet to find any connector that will compete with the dynamic performance of these connectors at a similar price point

With respect to tarnish - none of my connectors are exhibiting any signs of tarnish on the "contact areas" of the plugs and that is after approximately 6 years of continuous use.

Tarnish will only occur where an area is open to atmospheric Sulphur and due to the lack coal fired electricity up here in Canada the amount of Sulphur appears to be minimal

• e.g. The areas of the Banana plugs I currently use that is exposed to the "air" is only recently started to colour a very faint brownish tinge
• But the area inside the binding post is still very white.

For folk out there that dislikes the thought of any tarnish buildup I would suggest you use Gold.

Personally - I would ONLY choose Rhodium if there is no other option.

But that’s just "my personal preference"

Regards - Steve

@williewonka
A silver strike is one of the pretreatments that I was referring to for the proper adhesion of plated silver on copper. A silver strike is typically a very thin deposition of silver (fraction of a micron) from an electrolyte containing a low concentration of silver ions and high concentration of free cyanide as a complexing agent. From my experience these coatings do not produce a pure silver layer.

By the way, burning fossil fuels is not the only source of sulfur in the atmosphere. Sulfur is also released from the decomposition of sulfur containing organics and from volcanic activity and geothermal vents. So there is plenty of sulfur in the atmosphere, even in Canada.