Does cap type matter more the higher the operating voltages?

[Mark Hammer]

We've had numerous discussions here about cap types, and the frequent observation is that in a great many instances, cap type does not matter all that much.  At the same time, look at any informed lively discussion of amplifiers, and cap type seems to matter VERY much in just about every corner.

Of course much of the discussion I've run into as regards amps has to do with tube amps, rather than op-amps powered by +/-15v driving a couple of output transistors running at +/-30v or something like that.  So naturally, the question occurs to me that maybe cap composition is more a question of how the dielectric behaves under high operating voltages.  In other words, it is not that cap types do OR don't matter per se, but that they matter under circumstances that pertain to some contexts, but not that much to others.

Am I on the right track here?

[petemoore]

  I put a batch of Mylars in a 5e3, mostly .039ufs replacing .1uf's Orange Drops.
  My other 5e3 uses all the 'stock' Orange Drop caps...sounds much less 'ferty'..
  ie the one with the Mylars in it has an undesirable 'ghost tone', which is perfectly masked or helps if I distort with a stompbox, alone the amp is...exhibiting unwanted 'artifacts' compared to the one with all OD Caps...an instantly noticable difference...which of course could be caused by something else, I swap the Mylar for OD's very soon to get an even more difinitive conclusion on this.