Arny Krueger wrote:

"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.

Well, I think not, in the video, the eng describes how they tried to
measure the capacitors sensitivity to external sound, and they found
nothing. Their point was that internal resonances were taking place, and
as a SIDE EFFECT of this sound could at times be found to radiate from
the cap.

(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.


Yes, agreed, and I believe this is what ICW did, I was not trying to
test anything other than the assertion that caps would not produce any
sound. I assume the logic was that the paper claimed that the caps
resonate, and also produce sound, so by stating that they do not
actually produce sound the assumption seems to be that the posibility
that resonance takes place is removed.

Hopefully Jim will manage to find more details.


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


Hmm, and a single cap might be a load that would cause some amps problems.

--
Nick