[sdiy] Hand-matching capacitors for filter stages

[David G. Dixon]

> Well then, this is directly my question, what does better imply?

Precisely!  I can't see how one cap or another of similar capacitance would
make a filter sound "better" or "worse" than another one.  The only thing I
can think of is that better value matching among the caps in a filter would
make the filter cutoff track better, and would cause the circuit to
oscillate in a more predictable fashion at the critical gain threshold.
These are certainly desirable properties, but only relate to the
value-matching of the caps, not their dielectric properties (within
reasonable limits).

IMHO, if someone could detect an audible difference between otherwise
identical filters constructed with similarly well-matched and equal-valued
caps of polystyrene, polypropylene, or silvered mica, then that person has
superhuman hearing.

> Without hearing it or seeing a measurement in parallel how are we to
> ascertain sonic quality or difference when caps are inserted in circuit?
> 
> Can someone describe the sonic characteristic before or after cap
> changeout?
> 
> Or is there some other parameter or parameters we are measuring here
> besides acoustic properties such as frequency or resonance stability when
> Q is turned up etc.