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


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.
it is well established scientifically that at an interface of two different metals, a tiny voltage is generated

this is the principle on which thermocouples are based - the voltage is so small that it was not until the 1970s that amplifiers were developed to make wide spread use of this principle

what did you see that makes you think an audio distortion of a signal occurs due to this effect?
What got me thinking about it was a agon discussion I was reading where it was suggested that the receptacle and plug metals should be of the same metals.. Various other posts have suggested something similar, without everyone agreeing, of course. 

The main research I've seen on this was done by the military a while back, where it was shown to cause distortion of a measurable degree relative to other factors. I'll try to find some links to the research...

I'm definitely not saying that there aren't other things that screw up a signal, but this particular 'issue' is what is currently piquing my interest. 

Also, I'm not sure AC power should be considered a signal.. Though, from what I understand, distortion in its waveform is to be avoided..
Maybe I missed this, but people have had their gear welded directly to the wall receptacle copper to copper for years. Try a search of the forums.
The answer is no interface.I am trying to go copper to copper. .
@mechans yes! That's a great idea. Forget welding, let's just have our entire electrical systems cast out of copper, all electronics included. Then we can add everything else afterwards, like resistors, capacitors, diodes.. And we'll never have to worry about upgrading because you can't! Unless you buy a different house...
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.
Post removed 
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).
@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?

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.

That’s why I started this thread. My initial line of thinking about connectors was as you stated: copper on copper should be best. But then that’s obviously not true once you start listening with plated connectors.

So that got me thinking about all the other connections I make in a power cord and the ways in which they might influence the sound. Where does it matter most? Not to mention how the internal wiring is connected to the IEC inlet, or wiring of the receptacle..

The comment above about DC intrigues me.. How does a constant current negate distortion?
re soldered connections

ARC used to have a big soldering machine, but they sold it after listening tests indicated that hand soldering gave them better sound

go figure...

re Where does it matter most? - likely everything matters more in the signal chain not the AC line supply - don't forget they have transformers in them which will eliminate or reduce noise

What matters most is the speakers tho not the pre-amps, etc.
I don't use connectors for the most part. I direct solder my power cords, ICs, and use no connectors on my speaker cables. I don't use binding posts on my amps and use a Teflon or woiden posts  to clamp the output wires of my amp to bare speaker wire. 

All connectors degrade sound no matter how good the connector. I don't like the sound of silver plated copper based on listening tests, but can see why others may. 

I have not not gone so far as to hardwire my gear to the romex in my house. That my be a little extreme🤔
@grannyring what is it about the sound of silver plated copper that you don't like?  I'm curious, as I've pretty much switched completely to silver plated copper connectors and love it.  
So, to make myself feel right, I need to try and destroy all of your reasoning for not liking what I do.  Oh, wait, no that's not right at all.  I'm actually just straight up curious. ;-)

Well I developed tinnitus listening to silver coated wire and my doctor told me pure copper only😊

Just a personal bias and you can stick with your wire. I just found it a tad tilted up in the upper mids and I am very sensitive to that. But, not all silver coated wire sounds the same and I bet another brand may sound just great. 
Got it. I'm not looking for validation of my choices, so no worries. I just like to hear everyone's opinion.. I feel like it helps my perspective.

Maybe I'm not finding my cables too bright because I'm only using silver plated copper connectors. All my cables are copper..