[sdiy] Hand-matching capacitors for filter stages

[David G. Dixon]

> I often use polystyrene
> capacitors for filters, since these are widely regarded as the best,
> and breadboard experiments I've done do tend to support this.

How are they better, exactly?  Does the filter sound better?  Is the
filter's transfer function closer to the theoretical?

I've never used (or even seen) a polystyrene cap, because they are too
inconvenient to obtain, and I loathe inconvenience.  I've used silvered
mica, metallized polypropylene, and C0G ceramics, and they all seem to work
pretty well.  Polystyrene caps are famous for having low leakage, but many
others are nearly as low.  What specific quality of polystyrene is so
desirable for filters, and how exactly does this enhance the filter's
performance?