Replacing Passive Components Replacing Passive Components to Improve Sound Quality by Paul J. Stamler From reading circuit design texts, one would think that a capacitor is just a capacitor and that different types are interchangeable in practical use. At the transition frequency where the device changes from capacitative to inductive behavior, there is a minimum impedance that can be thought of as a resistance in series with the capacitor. In any application, but especially in power supply capacitors, the lower ESR units perform better.
Capacitors also leak.
Replacing capacitors with low-leakage units is always a good idea. This can lead to audible problems, including smeared bass notes and the muddied rhythms. Unfortunately, they also pack a lot of dielectric absorption, ESR, and leakages so they need to be used with discretion in audio circuits. It's been an unfortunate tendency among circuit designers to use polar electrolytic capacitors as coupling caps in audio circuits, even audio circuits that have no DC on either side of the capacitor. This is a bad idea because you subject the capacitor to backwards voltages on half of every cycle of audio.