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Microphonic film capacitor

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The reason for microphonic sensitivity could be either a piezoelectric effect, or (maybe) piezoresistance. Piezoresistance (actually leakage in the insulator) would have response at twice the injected frequency.

Small-size ceramic capacitors use piezoelectric materials (rutile and titanates), but a wide range of ceramic materials is available, you'll have to buy and try. NPO should be fine, but C values are small.

Polymers aren't intrinsically piezoelectric; plastic film becomes polarizable because of internal strains, so look for mechanically weak dielectrics. I'd expect polystyrene capacitors (like Mallory SX series) to be nonmicrophonic just because styrene is a weak plastic.

Aluminum electrolytic should be fine for your low-pass application. That dielectric, Al2O3, is definitely NOT piezoelectric.

Reply to
whit3rd
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The most microphonic caps I've ever met were poorly manufactured electrolytics. The 'capacitor pill' wasn't securely located in the can. The re-work that involved ! Thanks purchasing.

Then there was the batch of TL072s the MD insisted on buying cheap ( they'd been soaked in a leaky container during shipping ). LMAO. What the guys behind desks do is something else.

Graham

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

Reply to
Eeyore

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Funny thing though is surface mount resistors measure as about the most ideal resistor you could imagine. The ESL is just the electrical length.

I can see through-hole parts have less microphonics since the lead itself relieves stress on the part.

Reply to
miso

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Generally the guys behind the desk sink the company, but make sure they have a golden parachute.

Reply to
miso

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Sadly the surface mount resistive film has more excess noise than metal film leaded. You can HEAR the difference. The material used is grossly inferior. It's even on the data sheets where the manufacturer dains to publish the numbers.

Plus, the dielectric films used in SMT caps and the construction don't match what we audio pros are used to.

Graham

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

Reply to
Eeyore

electrolytics.

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been

desks do

Time for change. Politics and dumb politicians are no different. I LOATHE most of them. There a FEW good 'uns though, bless them.

Graham

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

Reply to
Eeyore

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You need to learn about PVF2. Hellishly piezoelectric.

Reply to
JosephKK

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I don't doubt the differences. My point is strictly on parasitics. The chip resistors measure well.

Reply to
miso

Thanks; i can dig that out if i need it. Always thught glass caps were cool...

Reply to
Robert Baer

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Depends on the brand and type..witness those old Sprague caps!

Reply to
Robert Baer

involved

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desks do

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...so, rats that sink ships do not use lifeboats - they use golden parachutes. Someone needs to learn how to cut certain strings....

Reply to
Robert Baer

olytics.

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When they write the book on this decade, "too big to fail" will be in the lexicon.

Reply to
miso

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Well my reading on that is that it would damage the interests of the real big money types. I have a better idea, get rid of the tortured tax laws that help create megacorporations that cannot be brought to account for their deeds.

Reply to
JosephKK

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