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24.27.41.140
In Reply to: RE: Vexunga capacitors....a worthy and cost effective option to GE and ASC oil capacitors. posted by Iczerman on November 03, 2024 at 17:45:01
Polypropylene is the way to go. Much lower dielectric absorption than oil caps.
Follow Ups:
Polypropylene in Oil. I've got a few ASC motor-run caps described in the data sheet as (metalized?) polypropylene in "spearinol" oil. You can feel the oil sloshing about inside the can if you shake it. IIRC, ASC claims the oil provides cooling, environmental ruggedness and electrical durability.
Haven't seen tests for those, but there's no reason to believe the oil would make DA better . I would consider it an unnecessary contaminant for purposes of passing signal in an audio amplifier.
Besides DA issues:
The "oil" may help with piezoelectric effects by displacing any air between plates and adding mass.
We have had problems with Class 2 ceramics at work being piezoelectric enough that you can see the vibration frequency in the RF output to the antenna. The Class 1 ceramics didn't have the problem, but were bigger and more costly.
I've also run into issues with the high CV product Class 2 ceramics where there is both a very strong drop in capacitance with applied voltage and the aging rate (drop in capacitance with time) is higher than the lower CV product Class 2 ceramic capacitors.
Play safe and play longer! Don't be an "OUCH!" casualty.
Unplug it, discharge it and measure it (twice) before you touch it.
. . .Oh!. . .Remember: Modifying things voids their warranty.
Caps are for PS filtering. Depending on one's interpretation of the term "signal path" I would think these caps pass no signal at any time . . . Except maybe the output cap . . .
On a related subject: Capcitor dielectric absorption (da) is frequently cited as a significant source of capacitor "sound" and distortion if excessive. The typical simplified electrical model of da reveals to me how the characteristic could be a real problem in some apps like an analog integrator or sample and hold. But for an AC signal or audio, the means of signal damage isn't obvious. The da models I've seen aren't too complex. So I'm wondering if anyone has ever simulated da effects in spice? Or conducted physical experiments?
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