In systems like the power feed or amplifier feeds, the output impedance of the power source is very low. Because of this, the capacitance between the two conductors is not important. The series inductance is important because current transients that surge through the wires will meet with extra resistance due to the inductive reactance. This will create a transient voltage drop over the length of the cable. For instance 117VAC becomes 116ACV momentarily. The length of the cable is proportional to the inductance. Longer cable, more inductance.
In the case of the power cord to a power amplifier, anything that limits the current inrush that would normally recharge the amplifier power-supply capacitor bank after it is momentarily discharged, can cause a voltage droop at the power output transistors. Any significant momentary droop at the output transistors can cause audible distortion. You can think of the capacitor bank as both a filter to eliminate 60 Hz (to create DC) AND a battery of sorts that stores DC power potential to be expended when the power transistors demand it during high-power transients. When high-power is demanded, the capacitor-bank (battery) actually depletes, the voltage at the transistors eventually dropping as a result. To counteract this, the rectified AC power directly recharges the caps every half-cycle when the recitifiers are conducting. If the power-cord is inductive (as most rubber cords are), then this recharging action can be limited. If there is no high-current demand from the music, the caps just get charged initially and then very little additional current is drawn from the AC power cord.
In the case of the power cord to a power amplifier, anything that limits the current inrush that would normally recharge the amplifier power-supply capacitor bank after it is momentarily discharged, can cause a voltage droop at the power output transistors. Any significant momentary droop at the output transistors can cause audible distortion. You can think of the capacitor bank as both a filter to eliminate 60 Hz (to create DC) AND a battery of sorts that stores DC power potential to be expended when the power transistors demand it during high-power transients. When high-power is demanded, the capacitor-bank (battery) actually depletes, the voltage at the transistors eventually dropping as a result. To counteract this, the rectified AC power directly recharges the caps every half-cycle when the recitifiers are conducting. If the power-cord is inductive (as most rubber cords are), then this recharging action can be limited. If there is no high-current demand from the music, the caps just get charged initially and then very little additional current is drawn from the AC power cord.