To All Cable Deniers, 1 Very Simple Question.

Usually in those cable free-for-alls, the more ignorant of science and less educated the posters are, the more strident and unmoored from reality they sound. On both sides.

@bigtwin   I assumed it is about cables in general, plug being just an example, since title says "To All Cable Deniers"

I meant +1 @mitch2 !

The OP implies that he can hear the difference between the copper content of the plug pins.  I would like to hear an outright statement about his findings.

I gave Gemini a slightly different perspective to come up with an answer. 
My prompt was:

How do different alloys and plating of an AC connector plug prongs affect conductivity. 
And if conductivity is affected, can power delivery change the way an audio component’s power supply behaves?
 

Here’s the response:

When it comes to high-end audio, the "last inch" of the power chain—the AC plug—is a subject of intense debate. While the physics of conductivity are straightforward, the way those changes manifest in sensitive audio power supplies involves a bit more nuance.
1. Material Conductivity vs. Plating
In the world of AC connectors, we rarely use pure silver or copper for the prongs because they are too soft for repeated plugging. Instead, we use alloys and plating layers.
Here is how common materials rank in terms of electrical conductivity (relative to the IACS - International Annealed Copper Standard):
| Material | Conductivity (% IACS) | Common Use |
|---|---|---|
| Silver | ~105% | High-end plating |
| Copper (Pure) | 100% | High-end base material (often "Tellurium Copper" for hardness) |
| Gold | ~70% | Plating (prevents corrosion) |
| Brass | ~25–28% | Standard industrial plugs |
| Nickel | ~22% | Barrier layer/Cheap plating |
| Rhodium | ~35% | High-end plating (extremely durable/hard) |
The Layer Cake Effect
Most "Gold" or "Rhodium" plugs aren't solid gold; they are brass or copper with layers.
 * The Barrier Layer: Manufacturers often plate Nickel over copper before adding gold. Since nickel has lower conductivity and magnetic properties, some audiophiles argue it creates a "bottleneck" or adds a specific sonic signature.
 * Oxidation: Copper and silver oxidize (though silver oxide remains conductive), whereas gold and rhodium do not. This ensures long-term "contact integrity."
2. Impact on Power Supply Behavior
Does a change in conductivity actually change how a power supply behaves? Physically, the difference in resistance (R) between a brass plug and a silver-plated copper plug is measured in milliohms (m\Omega).
In a vacuum, this change is negligible. However, audio power supplies (especially linear ones) behave differently than a simple lightbulb:
Instantaneous Current Demand
Audio amplifiers don't draw power in a smooth, constant stream. When a heavy bass note hits, the power supply's filter capacitors need to recharge instantly. This creates high-current "gulps" from the AC line.
 * Voltage Drop: If the connector has higher resistance or poor contact tension, these micro-bursts of current can cause a momentary voltage drop.
 * Power Factor & Noise: High-quality alloys and tight tolerances reduce contact impedance. Lower impedance at the plug ensures the power supply can "draw" current with the least amount of restriction, which can theoretically reduce the ripple voltage in the DC stage of the power supply.
High-Frequency Noise
Plating materials like Rhodium are incredibly hard. While slightly less conductive than gold, they resist micro-arcing and surface wear. A cleaner contact surface reduces Rectification Noise—tiny sparks or "noise" generated when current jumps across microscopic gaps in a poor connection.
The "Audiophile" Perspective
While a skeptical engineer might point out that there are miles of generic copper wire behind your wall, the counter-argument is that the connector is a mechanical junction. Mechanical junctions are where most electrical noise and resistance spikes occur.
 * Gold tends to sound "warmer" or "smoother" to many listeners, likely due to the softer metal's contact patch.
 * Silver/Rhodium is often described as "detailed" or "fast," which proponents attribute to higher conductivity and better transient response for the power transformer.
Would you like me to compare specific connector brands or explain how "cryogenic treatment" of these alloys is supposed to work?