PP filter caps in a 18watt?

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musicheals
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PP filter caps in a 18watt?

Post by musicheals »

Hi all at 18watt,
a few months ago I had the idea of replacing all the electrolyte filter caps in an EL84 amp with PP film caps. The fact that in recent times this caps are not so large than in 10 years ago encourages me for a try. The prices for a 20uF/500V range between 6 -10 €. So quite a bit cheaper than a Sprague Atom.
The ESR of the PP is much lower than in any electrolyte caps.
The other good thing is it's increased lifetime.
So here's my question: did any of you in the forum gave PPs a try?
More important for me: will it bring any advantage in feel, response speed, sound or something else?

Thanks a lot
musicheals
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TriodeLuvr
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Re: PP filter caps in a 18watt?

Post by TriodeLuvr »

I've been thinking about this for hi-fi amps. Some of the less expensive Kemet films at 20uF or 25uF are rated for less than 5 milliohm ESR. That's a major improvement from just 10 years ago. The question is whether this would be beneficial in an analog tube amplifier. Even in hi-fi, where we often talk about nuance and small signal fidelity, I'm somewhat skeptical. There's a lot of resistance built into the amplifier's native circuitry. Is it helpful to have such a low series resistance in the power supply when we have 100K anode resistors? And what about the DC resistance of the output transformer? That's huge, compared to film caps. On the other hand, like you say, the longer life of these parts and their aging characteristics might be sufficient in itself to warrant their use. It would be nice if all the electrolytics could be replaced with more "permanent" components.

I'd be interested in trying film caps in a low wattage Class A amp. Something like a single-ended 6V6 or EL84 could use a CLC supply with 20uF caps. My gut feel for this says whatever audible improvements might be had are more likely to be apparent in an amplifier of that type, rather than an AB1 amplifier at 15W or more.

Jack
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musicheals
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Re: PP filter caps in a 18watt?

Post by musicheals »

Yes I agree with you. Maybe no audible effect, but I'm sure in the future many guitar and hi-fi amps will be equipped with film caps. Simply because they will get even cheaper and because they have many advantages over the electrolyte caps...

musicheals
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