Crossover capacitors

[Bill Shenefelt]

I have some "old" caps from JBL better crossover networks including 22uF ones. They resemble a short section of a paper towel roller, a cardboard "tube" about 2.5 inches long by an inch in diameter with a white internal resembling wax showing on both ends and two wires at one end. What are they some sort of oil soaked paper inside with wax to prevent drying out or what. They still measure the value they did years ago and I am going to reuse them but I am curious at to what "class" of a non electrolytic they are?

 

[A9X]

^^ Yes they're colloquially known as paper-in-oil caps. They're OK, and have a bit of a cult following amongst some of the tweakier (<- not a compliment) tube amp builders. They're better than electros but I certainly wouldn't use them in place of a good polypropylene.