Does removing the plastic covers on caps help?

I recently had some caps installed in my SS amp by a professional audio equipment modifier. When I asked him what else I could do to improve the sound, he told me that an old tweaker secret was to remove the plastic wrapping on all capacitors. He said there was a dielectric effect similar to that found in cables, and that removing the plastic usually resulted in more "air"

Since it costs nothing, I'm certainly willing to give it a try, but just wondered if anybody else has heard of this or has firsthand experience with this sinple technique.
Two sides to this story. Both of them have to do with capacitors ringing and / or being microphonic. Leaving the plastic on may reduce ringing and damp the level of microphonics that a cap is suffering from. Removing the plastic will raise the frequency of resonance, which can contribute to some interpreting the more pronounced high frequency oscillation as having "more air" or increased high frequency "detail".

Many "tweakers" that actually know what they are doing, use test equipment to verify what works and what doesn't, have access to accelerometers, etc... will damp or mass load capacitors to get away from the very problems mentioned above. This can tend to make the circuit sound "deader", so you've got to have things pretty well straight before attempting to do anything like this. As such, i would consider anyone that encourages such a tweak as increasing the amount of ringing or microphonics of a device as being both unskilled and resorting to "band-aids" on a product that is simply not working well to begin with. That is, unless they are taking steps above and beyond the outer plastic cover to damp capacitor vibrations.

If you doubt these comments, try looking in the AA "tweaks" archive as capacitor ringing and microphonics have been discussed there on several different occassions. Here's a real short thread about vibrating capacitors that covers some of this. Here's another post about mass loading capacitors that goes into detail posted by someone that seems to have done quite a bit of research on the subject. Obviously, you'll find different points of view on the subject with varying levels of expertise in the field.

As a side note, cap's tend to start to ring when their legs are excited. If you have a few caps laying around ( Solen's work great as an example ), hold the body and "flick" the longest lead that is attached to its' body. Chances are, you'll hear the cap literally "break into song". As such, one should strive to keep capacitor legs as short as possible and take steps to damp the legs and / or the vibration transfered into the cap body if one is concerned about "the ultimate in performance". The use of generic "Blu Tak" ( sp ??? ) wrapped around the leads at the point of entry into the cap body can help to decouple any external vibrations.

Speaking of capacitor legs, most of them are made out of a very low grade conductor as a general rule. Some of the better caps make use of copper leads that are covered in heat shrink to minimize both corrosion from exposure to air and to act as a "damper" via mass loading to keep the legs from ringing and transfering energy into the cap body. If you want to improve the caps that you have, you can simply cut off their tinned leads relatively close to the capacitor body and replace them with the wire of your choice. The key thing here is to make a solid electrical and physical connection between the wire and the remaining leg of the cap prior to applying any solder to the connection. One should not rely on the solder itself to make the connection as this may result in taking a step backwards sonically. Sean
The comment above assumes that the plastic around an electrolytic capacitor is an integral part of the design and is used to damp vibrations. Given that 99% of capacitors found in high-end equipment are also used in computers, calculators, VCR's, etc, where "good sound" is not an issue, I really doubt this is true. Besides, how much engineering do you think goes into a run-of-the-mill $.15 capacitor?

The way I see it, the plastic shrink wrap serves two purposes, one, to act as a "billboard" to display the type and size of the capacitor and a clear way to deliniate the negative lead, and two, as an insulator to reduce the possibility of other leads in the circuit shorting against the aluminum can.

I have removed the plastic from capacitors in the PS of both amp and pre, as well as all plastic from the digital caps in my CD sources, and feel it is a worthwhile tweak. I attribute the increase in bloom and resolution a product of eliminating both the dielectric effect and a potential source of static charge (plastic).

For what its worth, all the capacitors in 47 Lab gear are "naked".
I agree with some of the points that you bring up Mbhcid. The plastic covering is more of an afterthought by most manufacturers to say the least and is primarily used as an insulator and as a means of identification. Having said that, that does not mean that it can't have benefits or drawbacks that may not have been originally taken into consideration. As such, i don't see a problem with removing the "case coverings" so long as the parts are easily identified in terms of values and there steps are taken to reduce the potential for something to short out against the body of the caps. Whether or not someone likes the sound difference that this "tweak" achieves is strictly a matter of personal taste.

As far as the reference to 47 Lab's gear, i've never heard any of it but i do know what it measures like. That is, they are very poor performers that are poorly designed and highly unstable. The signal that goes into these devices looks nothing like what comes out, meaning that there is a complete lack of accurate signal reproduction and / or large quantities of non-linear amplification taking place. Should someone like the sound that these products produce, so be it. I'm not about to say that someone can or can't like something. Using them as a point of reference for "quality" audio reproduction is something all-together different though. Sean
Really not worth getting into here, but you should audition some 47 Labs gear when you get a chance - It will make you realize "measured performance" has absolutely nothing to do with musicality.

Keep an open mind and don't shortchange yourself.
Plastic does not sound good as a reducer, thats why they (and I) remove plastic from caps, and also transformers. Notice a nice improvement whenever I do both.

Yes I do notice more "air" which could have something to do with "ringing" I would suppose, but I do understand about the poor conductors manu. use to make them. Best to keep them short as possible!
Thanks to all those responding. Very informative discussion, and again, I'm awed by the collective knowledge of those on this board and the time they take to share it with others.

I was unaware of the need to check caps for damping, but it certainly makes sense after reading the above comments and links. In my particular amp mod, the Black Gates are so much bigger than the stock caps that they had to be mounted standing above the PCB on longer leads.

I'll definitely study the best way to damp them so they don't sing like tuning forks. I'm guessing that's exactly what they are doing in the present set-up now that the symptoms have been described.
If you find that damping works or makes a difference on your BG's, I would be very interested to hear about it.

I have been considering removing all of the plastic, but now I am reluctant.


I am much more favorably inclined towards removing capacitor covers than some of the above posts. The audible consequences are not insignificant and cumulative. If the desired effect is not achieved, it is always possible to experiment with various damping techniques for tuning: C37 lacquer, Sorbothane, EAR ISODAMP, acrylic shells--I have even seen nuded capacitors attached to violin bridges.
Sean, which 47 Labs products have you seen measurements for? Are you referring to the Stereophile measurements of Gaincard or other measurements of other products? And, one last question: Were proper testing techniques used? I ask, because, in the measurement of integrated circuits, it is very easy to come up with erroneous results, esp. when comparing integrated amplifiers to discrete amplifier designs.
I agree that removing the plastic will change the sound of the device. The question is, are you willing to take the chance of altering the sonics of a device that you already like and paid good money for ? Who is to say that you will like the change ? If you don't, what do you do ? Yes, you can attempt to damp the caps using other methods, but can you strike the same basic sonic signature that drew you to that component to begin with ? Obviously, there are a LOT of questions to think about before doing what is a non-reversable mod. The only way to really reverse such a mod is to replace the caps or try to replace the plastic using some type of adhesive. All i can say to that is "good luck". If you really want to try this, start slowly and do this systematically. Choose two caps ( one in the right channel, one in the left ) and go from there. If you notice no difference or like what you hear, do two more. If worse comes to worse, you can always back up and replace two caps and be done with it.

Other than that, i agree with Asi Tek. That is, one should always strive to keep the legs of any capacitor as short as is feasibly possible.

Slawney: The test results that i saw were the ones taken in Stereophile. I "assumed" that JA took the measurements using the same approach that he did with all the other gear that he has tested. I can't remember the specifics of the tests or test results but i do remember that the components did not test very well at all. They also looked to be quite sensitive to what was connected to them, making them less than versatile. Sean