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In Reply to: Depends where in the circuit it is... posted by Allen Wright on March 18, 2007 at 04:39:03:
i also wish to replace a nonpolar electrolytic with a film capacitor at the input of a solid state power amp. the nonpolar is a 100uf 10 v
cap in series with the rca input jack. i want to replace it with a 2.2 uf 63v dc rated film cap. is this reasonable or must i use a larger cap.
space is an issue on the circuit board.
Follow Ups:
HI,
This is the proposition I was answering:"i also wish to replace a nonpolar electrolytic with a film capacitor at the input of a solid state power amp. the nonpolar is a 100uf 10 v
cap in series with the rca input jack. i want to replace it with a 2.2 uf 63v dc rated film cap. is this reasonable or must i use a larger cap.
space is an issue on the circuit board"As stated, this won't work properly.
HI,
No, you must use a cap with the same or more capacitance or you will suffer low frequency roll off. With the example you gave, the roll off would be severe.Electrolytics are used because the same capacitance in a plastic or mylar capacitor would be physically huge. The substitution can certainly be done but you better have a lot of space. The voltage rating would be about the same for a plastic capacitor. It's not too critical but don't go lower.
Sparky
i dont understand your reply. my amp has an input impedence of 35K ohms. i have schematics of other solid state amps with similar input impedences using input film caps of 1.0 uf to 4.7 uf. my understanding is that manufacturers used these 100uf nonpolar elecrolytics or two back to back polar electrolytics only because they were cheaper than a film cap.
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