Microphonic film capacitor

Don't tap it with a plastic rod?

John

Sno-o-o-ort ;-)

...Jim Thompson

Ceramics can be FAR WORSE... If you can find a "film" capacitor where the plastic sheet has been coated by sputtering and/or depositon, that constuctionshould be the least sensitive.

Has anyone compared through-hole film caps vs. SMT as far as microphonics goes?

If possible, avoid having any substantial DC voltage across the cap-- that will minimize voltage fluctuations as a result of transient changes in capacitance.

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t be a

PD

Thanks for the tip. Unfortunately, these are loop filter integrator caps, and need to have between 1 and 15V across them.

The previous version of my board had through hole filter components (Poly Layer caps) and that is microphonic also I discovered last night.

My options seem to be:

1. Tantalums
2. Re-design filter with smaller caps (could try NPO/COG) and larger resistors
3. Miniature aluminium electrolytics

"Spehro Pefhany" wrote

Just tried this. At the bottom end of my tuning range, where the cap voltage is small, I see no detectable microphonics. At the top end, where I have almost 15V on the cap, hitting the board produces a large frequency deviation spike. I'm very dissappointed with this Panasonic film cap; it looks nice, with rainbow colours as it catches the light; but it doesn't work.

Dow Corning do some nice glass caps but they may not have the values you want.

...

LOL!

("Doctor, it hurts when I do this." "So, don't do that.")

Cheers! Rich

I've now tried:

1. Film 1210 16V (the original)
2. Tantalum 0603 16V
3. Ceramic X7R 1210 50V
4. Radial aluminium electrolytic 63V (15 years old)

Guess which: a. was better than the film but still a bit microphonic. b. can hear a pin drop next door. c. has no microphonics whatsoever.

Good idea..the SMTs are more likely to be made by sputtering or depositionof the metallization.

Are they still being made??

Betcha the X7R was the worst, with the Olde Sprague being the best...

Correct :-)

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be a

Green Xenon will think you have a condenser microphone.

G=B2

As far as I know ! Someone posted a link to the manufacturers data sheets recently. I belive it was AVX. I have a copy of the pdf if you want it.

SMT caps have a dreadful reputation in audio. Try substituting with a polypropylene or even polyester type with leads temporarily.

SMT resistors can be pretty crappy too.

Graham

-- due to the hugely increased level of spam please make the obvious adjustment to my email address

Serious audio uses through hole components for all passives. WE KNOW there's a difference.

Graham

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Aluminium electrolytics can be the most microphonic of all.

Graham

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