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PhopsonNY 14th September 2002 09:42 PM

Removing Plastic covers from Capacitors
Hi there,

I read at tip at the website of claiming that removing the plastic covers from capacitors gives greater performance...

Does anyone know this to be true?

If so what types of improvements were noted and what is the reason for this phenomenon?


peranders 14th September 2002 10:43 PM

I don't belive this at all, in fact I think you will ruin the cap. Is it possible to remove the cover without damaging the cap? We have talked here about capacitor distorsion

and come to the conclusion that the distortion is very small. It's better to take care of the circuit design instead.

artnyos 14th September 2002 10:56 PM

Cap Mods
It is very easy to try and will not ruin the cap. You can run a soldering iron across the plastic and peel it right off. Mark the leads for polarity if you do this befor installing cap. I have heared differences from putting damping material on caps. "Maybe this is a little "extreme" for Peranders. It is pretty well accepted that caps sound different even among electrolytics.

Peter Daniel 14th September 2002 11:02 PM


If you would check my thread:, you would already know that proper combining of materials and structural support, are as important as circuits themselves. It is still only my opinions, but by doing a lot of experimentation in that field I'm more and more certain of that.;)

Depending what I placed under my CD-PRO transport I got completely different sound. Sometimes it sounded worse than cheap $100 player, sometimes it was high end sound.

I've also heard that removing plastic covers from electrolytics improves sonics. You got two different materials interacting with ea. other. When you remove one the vibrational properties change and possible change in sound signature could be observed.

I didn't try it yet (I'm using 120 electrolytics in my current amp) and I'm also very reluctant to remove that nice plastic from my 22,000 Cerafine caps.;)

But it can be easily done, just cut the plasic (but not completely, so as not to scratch aluminum) and pull it off. We would be curious to hear your obsevations.

ThingyNess 14th September 2002 11:03 PM

On aluminum electrolytics at least, you can remove the plastic from the outside and gain a little better heat dissipation, and therefore a higher ripple current capability. I wouldn't try unwrapping the plastic on a film (polyester, polypropylene, etc) capacitor though, as I've seen some of them where the film on the outside is just a continuation of the dielectric, and if you unwrap it, you'll unwrap the whole capacitor.

Of course, this is unnecessary and won't make a difference unless you're really pushing the limits of the capacitors' ripple current capability.

(and it won't make them sound better - it'll just give them a little bit longer life, all other things being equal)

Peter Daniel 14th September 2002 11:10 PM

and it won't make them sound better
ThingyNess, take a Coke can and put some plastic around it, then compare the sound when you knock on it. Is it different?;)

I'll go even further: do you have a preferance for the sound of Coke can with a plastic or without it? Expect similar differences in sound for caps with plastic and without it. I'm not joking.;)

Bill Fitzpatrick 14th September 2002 11:27 PM



In fact, recent reseach suggests that power amplifiers (and electrolytics) should be operated in sealed glass containers in which the air has been replaced with argon. Input and output connections are made via feedthrus. The temperature must be reduced to -100C over a period of 10 years.

We a currently running a $29.95 special on this process. This offer ends Oct 15, 2002 so send us your amps and a check today.

ThingyNess 14th September 2002 11:34 PM


Take an audio signal (say 5V pk-pk as it gives us a better S/N ratio for our test, high voltages being better) audio signal (your choice which kind, sines are nice as they're easy to analyze) and alternately pass it through two electrolytic capacitors (one with the plastic on, and one with the plastic off.)

Examine the output of each on a 'scope. Note any differences you see.

Now take a large screwdriver and smack each capacitor around a bit - on the top, bottom, sides, etc. Again, note any fluctuations or oddities in the 'scope readout. For more fun, use a digital 'scope and capture the waveform as you do this so you can examine it later for any transients you may miss on an analog scope.

Worrying about mechanical resonances is one thing when you're dealing with a device that's designed specifically for electrical -> mechanical energy conversion (IE, a loudspeaker), but a completely different thing when you're talking about mechanical resonances in a device designed to pass the signal electrically.

Of course, you can generalize this as much as you want - grab yourself a distortion analyzer, capture the output of the distortion analyzer with a 'scope, and during the test, take an 8 pound sledge and start beating the hell out of your favorite amp. It can be quite a fun test. :)

Considering the fact that moving my head the amount required to scratch my ear likely changes the frequency/phase response more than any esoteric tweak you could do to your system, I'm not about to go and worry about mechanical damping in my amplifiers anytime soon - spending 5 minutes tweaking the bracing/damping on your speakers will likely have more effect than a lifetime of rubber isolation mounts for your non-transducer audio gear.

Of course, many people love the subjective part of audio, and if you consider yourself a subjectivist, by all means, remove the plastic. While you're at it, you might want to slip a woven carbon fiber "sock" over the cap - I hear those sound much better than the inferior wool ones. :)

Besides, in a lot of psychological (and even physiological) tests, the placebo does almost as well as the real thing. The power of suggestion is a strong one indeed. ;)

(for what it's worth, I find most of the stuff you've posted here to be beautifully designed/constructed, Peter, and I wish I could make my DIY efforts look that good.)

artnyos 14th September 2002 11:41 PM

Well you can lead a horse to water but you get make him hear.
I used some material from 3M for damping fan assembly noise in a telecom application and it was made of thin aluminum with an adhesive backing. The aluminum was part of the damping mechanism. I was told explicitly not to put material over the aluminum. Good thing I found out those guys at 3M are just a bunch of flakey tweak types, I will never be hoodwinked by them again. Thanks for seting me straight.


P.S. Are you a material science engineer or a mechnical engineer?

artnyos 14th September 2002 11:55 PM

Another Expert.......

Worrying about mechanical resonances is one thing when you're dealing with a device that's designed specifically for electrical -> mechanical energy conversion (IE, a loudspeaker), but a completely different thing when you're talking about mechanical resonances in a device designed to pass the signal electrically.

Go read Chapter 26. Analog Extensions of Digital Time and Frequency generation in Analog Circuit Design edited by Jim Williams. The author describes the effect of noise and vibration on sensitive oscillator circuit. By the way these were real engineers and not audio tweaks. If I had a quater for every time I heard the phase "That shouldn't matter..." in my telecom engineering career...:magnify:

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