Best way to dampen a micro-vibrating Printed Circuit Board inside an amp? Thanks!

Not sure about tinkering inside the amp, but many people will put isolation footers under the bottom of the amp.  Might make sense to start there?

You'd have to dismount from chassis, support with sorbothane or some other substance. My previous pre, Joule Electra floated board in like manner.

Goop.

A clear glue that remains very flexible.Don't need too much. Only need a few connecting dots.