Ceramic vs Silver Mica

[Trace]

I wish I knew. All I know is that parallel caps don't sound the same as a single cap of the same measured value

If you do the research you will find that when you place two caps of the same material together that the signal will not pass through each cap identically or at the same time. Like other components caps have varying degrees of tolerances. With ceramic disc caps there can be anywhere from a 10% to 40% tolerance between two caps of the same value. As such the signal cannot pass through both caps at exactly the same times resulting in a phase shift.

A fun experiment; Meter out 4-5 ceramic disc caps that all meter out to the exact same value. Now A/B each in the same spot of the same circuit. While the caps all meter out the same you will usually find that they tend to sound and feel different under load.

Along a some what similar parallel; There have been a great deal of discolored/burn screen-grid resistors, coupling caps, etc that all metered out correctly but under load were failing. The over all theme I am trying to convey is that meters, scopes, etc will only show you so much.

In the end, we have to use our ears to help us determine what sounds as well as feels best to us as players. From time to time some of the best amp designers have tried their hand to impart some of this knowledge onto us but more times than not this falls on deaf ears (IE: when things that should not make a difference do make a difference). Nothing takes the place of hands on experience and in the never ending quest of tone we owe it to ourselves to experiment. More times than not the end results tend to surprise more than disappoint.


Hope it helps
Trace