Of all the cable upgrade claims in audio, the power cable is the most difficult to justify on engineering grounds. The argument that replacing a standard mains power cable with an exotic, heavily constructed alternative meaningfully improves audio performance requires a chain of reasoning that becomes increasingly implausible at each step.
The mains power cable connects the wall outlet to the amplifier’s IEC inlet. From there, the signal passes through the amplifier’s internal wiring, mains filter, rectifier, capacitor bank, voltage regulators, and output stage before emerging as an audio signal. The power supply design — the quality of its rectification, regulation, filtering, and reservoir capacitance — determines how effectively the amplifier converts raw mains power into a stable, low-noise supply rail. This is an engineering challenge of considerable sophistication, and one that competent amplifier designers address in the power supply itself.
The mains cable’s resistance over a 1 to 2 metre run is a fraction of a milliohm for any adequately sized conductor. The mains impedance of the household supply — typically 0.1 to 0.5 ohms depending on the installation — is orders of magnitude larger. The cable is not the limiting factor.
Shielding of power cables has some relevance in specific situations where RF interference is being conducted into the amplifier through the mains input. A well-shielded mains cable may reduce RF ingress in environments with high radio frequency contamination. This is a real phenomenon — but it is addressed by the amplifier’s mains filter, which is the correct and primary line of defence, and by appropriate earthing and supply quality rather than by the cable’s construction.
The sonic improvements attributed to premium power cables in listening evaluations are consistent with expectation effects — the well-documented tendency of listeners who believe a change has been made to perceive an improvement. Under controlled blind conditions, power cable differences have not been reliably demonstrated. The physics is clear on why.