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Where is the optimal place to have an interface between two different metals?

hey-o!

it is pretty well established scientifically as well as anecdotally that at an interface of two different conductors composed of two different metals, distortion of a signal occurs.  this leads many to choose receptacles and power plugs (as well as IEC inlets and connectors)  made from the same metal.

my question is this: where is the best place to have the interface between different metals in order to reduce distortion?  there obviously needs to be some type of interface since in-wall wiring is copper and internal component wiring is often copper as well. so where does it make the most difference? is it in the receptacle/plug interface where everyone who cares about this focuses their attention? or do they focus their attention here because any of the other interfaces are too much of a pain in the ass to change?  what about the power cable itself?  i see lots of people who like rhodium plated recept/plug combos, but i've never seen any mention of rhodium plated cable.. so there's an interface between two different metals where the connectors join to the cables...

i truly am curious and would love your thoughts and discoveries on the matter.
toddverrone
kijanki's avatar
kijanki
4,477 posts
 
Power cable has two conductors hence two junctions generating voltages in opposite directions that cancel each other.  Even with small DC voltage there would be no distortion, not to mention that there is always small amount of DC on AC lines.
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auxinput
2,921 posts
 
I've done a lot of listening with different types of metal connections.  I think there is a challenge with mating connections based on surface contact only.  Examples of this are power plugs and interconnect plugs (RCA/XLR).  If you are not using a soldered connection, then the surface material of the mating metals has a huge contribution to the sound.  In my experience, copper on copper or unplated-copper is not a good idea and creates a "ringing" distortion in the midrange.  This is where different plating really helps (such as gold or rhodium -- or even silver-plating if you like that sonic signature).
toddverrone's avatar
toddverrone OP
840 posts
 
@auxinput - so if the connection is soldered, that's not really an issue? I know with some signal cables, a junction between two different metals produces a difference in impedance that can cause a reflection of the signal to propagate back down the cable to the source. Is that not what is happening in power cables as well? Or is it more about just the sonic signature of each metal at the interface?
auxinput
2,921 posts
 

That's a good question.  If you are correct in saying that a junction between 2 DIFFERENT metals causes impedance related reflections, then one would assume that copper-on-copper would be the best outcome.  That would not jive with my experience on the copper-on-copper connectors causing midrange ringing distortions.  I honestly don't know why plated connectors work better than un-plated copper.

The only signal reflection problem I know of is related to digital signal cables only (SPDIF coax / HDMI) where shorter cable lengths (under 5 feet) will cause reflections back to signal origination and cause sound problems.  I can hear this in short digital cables where the sound is smeared some.

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