On 2008-08-22, Jim Lesurf wrote:
In article , Don Pearce
wrote:
Nick Gorham wrote:
Don Pearce wrote:
Nick Gorham wrote:
This might be of interest
http://www.sonicstate.com/news/shownews.cfm?newsid=6667

No, I listened again - I had it right.

I presume the above URL sends a 'stream' of some kind. My browser simply
tells me that it doesn't have a Flash plugin enabled and the page text
seems void of info.

Yes - you need a plug-in. I found it interesting for what he says
does NOT matter with respect to the vibration and resonance effects
he describes.

- The capacitor's vibration of which he talks is not caused by the
opposing currents flowing in the parallel plates [1].

- The vibration is connected with the voltage appearing across the
capacitor but it does not seem to be discernible at voltages less
than 12V. (That cuts out any problem to do with an effective coupling
capacitor).

- It's apparently nothing to do with tan delta (loss), the effective
series resistance (ESR) or the capacitance (the nominal value I assume).

- The reverse effect where a (very) high-level audio signal impinges on
the capacitor seems to produce no discernable result (an output voltage,
I assume). So much for capacitor microphony claims.


[1] I did the analysis of this effect some years ago for loudspeaker
cables and derived expressions for how the capacitance and inductance of
zip-cord speaker cable varied with current flow. The coefficients (of
dependence on the square of the current) in typical cases were in the 1-10
parts per billion range, IIRC. I decided they were too small to matter.

--
John Phillips