"Nick Gorham" wrote in message


I just tried the experiment on a few caps I have to hand.
The ones that produces a sound when driven by a sig gen
were a BC 368WKT 220nf, Acotronics MKP 47nf and a 2.2uf
ClarityCap SA. Ones that I tried that didn't prduce any
sound I could hear were from Solen and Mundorf.

Two problems:

(1) The stated problem seems to be not that the capacitor produces sound
(it's someplace inside the bowels of the enclosure) but that operating in a
sound field causes the capacitor's operation to be modulated by the sound
field.

(2) If you're going to test capacitors, it would seem that you would want to
test them as they are used. IOW with the kinds of voltages, currents and
sound fields that one sees in a loudspeaker.

Though as expected the level was very low, at the 2vRMS
5kHz from my sig gen, it needed the cap to be against the
ear, but it was clearly there.

Note that the output stages of some SS amps produce audible sounds related
to the signals that they are amplifying.