Following is the Panasonic datasheet for their leaded axial ceramic capacitors. You'll notice the dielectric varies depending on the capacitance - keep that in mind if you're wanting to keep your repairs true to the original sound of the amplifier's circuit.
The NPO types weren't always available in the larger values and you ended using one of the Y5* dielectric variants that were temperature dependent and became significantly microphonic as the capacitance got larger. Nonetheless, the ac transfer characteristics, and their non-linearity at small signal levels was often something you wanted to give a "characteristic sound" to a circuit.
(If you want to know more about capacitor sound, read Cyril Bateman's Capacitor Sound articles that appeared in Wireless World: I saw these have been published here:https://linearaudio.nl/cyril-batemans-capacitor-sound-articles
A lot of the film capacitor types give a "clean" sound or in the words of my old boss, "...those capacitors sound too bloody Hi-Fi and were not making any of that..." - the ceramics were used for good reason in most cases
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