silver mica or polystyrene

[Netlist]

I think I saw that principle a few times in FM tuners. Two wires wrapped together to make a very small capacitance.

Now I understand what those strange wires are.

/Hugo

[alaskanaudio]

Small value capacitors such as 10pf are used to trim the very high-end frequency response, usually well above the normal hearing range. In many cases these small value capacitors are also used to improve, or control phase shift to prevent oscillation above the 1 Mhz point. Since these frequencies are mostly in the RF range (radio frequency) we should use capacitors that have very good characteristics at RF frequencies. Silver micas are one such capacitor.

RF gimmick capacitors, those made by twisting wires together, are at times useful to find initial values of the actual amount of capacitance required. As a personnel preference I would not leave them in a audio circuit permanently. A better choice would be to use a small value trimmer capacitor for this purpose. These can be left in place or replaced with the proper value fixed capacitor later if desired.

John Fassotte
Alaskan Audio