Why have capacitors improved so much over the years?

Redwood, I bought most of mine from Surplus Sales of Nebraska, when I didn't make my own.

At the Surplus Sales website, click on 'capacitors' in the left column, then on 'air gap variable', then go to the 'quad' section. There are some with 4 sections, each of which maxes at 460pf, for about 1.9nF or 0.0019 uF when paralleled. With judicious design, one can create an RIAA network with values in that range.

Warning: they're big and expensive. But it's the best sound available.

@ieales - thanks for the link, cool history.

@terry9 thats a wild website… I have no idea what I’m even looking at with those air caps!

My visitor was Ken Stevens of  Convergent Audio Technology. His wife, I believe was from the WNY area.

Redwood, it’s just a matter of getting used to them. Capacitance is an effect of two conductors separated by an insulator. The bigger the plates (conductors), the more capacitance. The closer together, the bigger the capacitance.

Accordingly, the capacitors are made so that every other plate is connected together, and the shaft turns the plates so that they become close together and alternating. This increases capacitance to the maximum value, while turning past that place decreases the capacitance towards the minimum.

With the help of a meter you’ll figure it out in a few minutes. Nothing exotic here, the theory’s been known for 200 years.

Since you seem to be interested, one of the best books you can buy is an edition of Art of Electronics by Horowitz and Hill. First edition 1980, third edition just a few years ago.