Cap break-in question

[Neuronal]

So I'm getting ready to do the extended upgrade for a foreplay III, and before digging in I thought I would break in the caps that came with the kit using Grainger's method (from this thread https://forum.bottlehead.com/index.php?topic=80.0) - as I understand it, you take 2 10W/10 Ohm resistors, wire them in parallel, wire the cap in series, and plug this into a stereo speaker output with the red side plugged into the cap and the black side plugged into the resistor. I'm playing at a normal (loud-ish, but normal) volume. I attach a pic of what I did for reference.

Here is the totally odd thing - I've been doing this for 36 hours, and I just now leaned over the cap...and heard music!! The caps seem to be making sound as I drive them. Is this normal? Have I fried my caps? I took one of them out of the system to check its resistance (to see if it still charged) and it still charges up when I do that. Just making sure this is within normal limits, as I expected silence. I turned off my stereo for now just in case I was doing damage.

Thanks for any advice all of you might have - I have had so much fun building these kits, the one bright spot during the pandemic.

 

[Paul Birkeland]

A 200V rated capacitor isn't going to be bothered by what you're doing.

 

[Neuronal]

Thanks, Paul, I'll continue the break in. The fact that the caps are making music is weird though, no?

 

[Paul Birkeland]

Thanks, Paul, I'll continue the break in. The fact that the caps are making music is weird though, no?

From a Clarity Cap white paper:

"Mechanical Resonances

Then, we began to investigate a key feature of audio capacitors: the mechanical resonance.
This is a physical deformation of the capacitor walls which occurs as a result of the audio signal
passing through the component – much like an electrostatic speaker. This resonance is
dependent on the size, shape, materials and manufacturing parameters of the capacitors. This
effect has been known about for years as it plays a part in the impulse strength of capacitors.
However, the effect has never been considered to be significant enough to affect a hi-fi
system’s audio reproduction due to the low energy involved."

 

[Neuronal]

cool, thanks for passing that along!