Unplated copper spades/banana

@mitch2  That’s really interesting about rhodium being a worse conductor than gold — I would’ve thought the opposite and begs the question why it would be used at all on any connection.  If it’s mostly for “hardness” and protective qualities that’s not a worthwhile trade off for a decrease in sound quality for me as I’d be perfectly fine with gold or silver.  

Gauge 10 copper wire has resistance of 0.001 ohm per foot. Gold plating is typically 0.00001" thick. It adds additional resistance in order of 1 microohm (o.ooooo1 ohm). Perhaps there are other effects when signal is crossing boundary of two different metals, but resistance of plating is not important IMHO.

Most all wire is copper.  The difference between a gold plate does make a difference, but in the big scheme of things, the difference between a gold plate and naked copper is really really really small. Rather than having to polish the ends on all of my cables, I choose to go with plated ends.

My two cents.

On the conductivity scale, copper and gold are very similar and you won't hear an actual difference with the only useful testing (blind) but bare copper will tarnish and need to be cleaned periodically. 

Copper needs to be cleaned every 6 months or tarnishes  that’s why they are gold or rhodium plated