Burn in Capacitor phenomena


Hello,

I just wanted to post about something I've just experienced with burning capacitors and a theory on a contributing reason to why they may sound different with time on them.

I made a capacitor burn in rig that play's music through the capacitors for burn in. During startup of this rig I noticed as the electric pulses of music pass through the capacitors they vibrate. That is you can hear the capacitors playing music. Over time I've noticed the volume or vibrational amplitude seems to have gotten slightly smaller. I am just throwing this out there, but my hypothesis is; that as electricity passes through, there is heating and swelling of the parts, the parts then undergo greater pressures and a greater sense of malleability and stickyness for a lack of a better word. These parts begin to Stick together and oils or plastics begin to settle into imperfections in the surface of the foils, ie: the parts meld causing a less ressonant (or perhaps a coupled resonance allowing the capacitor to resonate as a whole) sum of parts.

Why else would the capacitor become percievably less quieter? Other than a drop in frequency or less resonant.
perhaps because it's burning out, haha, I hope not.

Anyway I notice a difference in capacitor sound quality with time, and typically it sounds better as a less resonant capacitor probably would.

Thoughts?
scutterflux
If new caps are microphonic, than the culprit may be not in caps. Active devices tube, transistors are more likely to react to microphony. Touching caps will give you humm won't it? It probably humms without touching to some degree.
Just wanted to mention All my new caps are doing this, I have some Vcap cutf that do it, some solen tftf that are doing it, they all seem to be doing it. I can't wait until my Duelund cast arrive, they are supposed to be very limited in their resonance and partly due to the high price, we'll see...
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Geoffkait:
All caps are apparently microphonic. That's why those tiny little 3 mm (contrained layer) VTS dots from Marigo when stuck onto the tops of all caps improve the sound.

...but when they go bad they're REALLY microphonic
its my understanding that most film capacitors are dielectric- 2 sheets placed side by side, then rolled tightly.Each sheet is one side of the electrical contact. During initial break in the voltage applied finds uneven gaps and a settling in process occurs where the use over time "irons out" the gaps because of the force of the voltage and the cap finally settles into steady state performance. Also possible that some chemical changes occur but chemistry isn't my cup of tea.
Capacitor microphonics are easily detected at the surface with a sensitive instrument microphone. Try placing a phono cartridge stylus on the cap's surface and listen to it rumble with the music. We use a laser vibrometer to quantify it during the design process. Our ABX focus groups confirmed that microphonic behavior is a key determinant of sonic performance.

ClarityCap OEM Sales
The better sounding/quality capacitors do seem built to address the issue of resonance and they are better damped.
Duelund is a prime example of high effort to minimize resonance.
Regards,
All caps are apparently microphonic. That's why those tiny little 3 mm (contrained layer) VTS dots from Marigo when stuck onto the tops of all caps improve the sound.

Cheers
Caps vibrate to the music. I can't say that I have heard them play music but they do vibrate. This topic was discussed when I worked at Westlake Audio and the owner took this into consideration when he chose caps for his products.
Agree with Paulsax. They become microphonic when they are about to die.
Had to replace many in my 30 years old preamp.
microphonic caps? new one on me. I have seen i on guitar amp tubes and some pedals but not on discrete components. that aside it seems risky to assume the nature of sound from a cap is linked to the sound of the system they are installed in. Sounds like your burn in rig is driving the crap out of those caps and likely just burning them up.
During startup of this rig I noticed as the electric pulses of music pass through the capacitors they vibrate. That is you can hear the capacitors playing music.

I've never seen vibrating capacitors and never heard them play music too.