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Please do not (hijack) argue the virtues of capacitors in this thread. Thankyou.

Since a capacitor is a pretty simple device, what advantage is there in paying +$30-$40 more for a brand-name capacitor (like RF), over a generic (like pyramid)?

 
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Well, in some cases, the more expensive Caps have some little do-dads like digital voltage readout and stuff like that, which don't really do much for you typically.

Capacitors have an Equivalent Series Resistance, ESR. The ESR supposedly affects how quickly and well the capacitor passes current onto the amp, in a case when the bass hit for example. Lower ESR is better, and some capacitors list their ESR, and can be compared. no capacitor is ideal, so there is some resistance within it, and that is the measurement, higher resistance just means more power wasted. I believe there are many other factors in a Capacitor, but this is the most commonly compared.

I've heard that all Capacitors are made from the same company, and are all the same, which maybe true, but i don't, know, i'm sure you chould research more. Given the same ESR and capacity, i'd just go with the cheaper one.

 
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Personally I doubt there is ANY noticable difference other than brand name

For example, consider a blank t-shirt with no logo on it. It will cost lik $20. Now take the same shirt and put a Gucci logo on it, now it's $200 for the same thing + a logo. Even if you get 2 caps of the same size with different specs, 1 brand name and 1 generic, I would be genuinely surprised if you could tell a difference in performance.

 
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maybe a difference in material for better conductivity of that sort? like the difference between all the different brands of wires... i mean its just wires, but some conducts better than other and have more strands.
in the case with caps, perhaps just like ed said, maybe some release and store charges faster than others.

 
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if you are looking for a quality capacitor, "sprague" is the one of the best. you have to understand that your looking for quality dielectric material. just because it has "rf" on it does not mean the electrolyte and plate material are the best. if you can find out who made the cap, you probably have a better chance of getting a better made capacitor. especially with large electrolytics. even new caps of this nature come off the shelf and fail.

other manufacturers are:

cornell dubilier
g.e.
mallory

hope this helps.

edit: when capacitors fail, they typically short out. this is where you risk damaging equipment. so quality is related to reliability, not name brand of the comany selling the cap, but of who actually made it.

 
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One costs more than the other.

 
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since when do capacitors use an electrolyte?

 
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like, other than electolytic capacitors???

 
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yea, the dielectric will vary by manufacturers...if it breaks down and plates short out, the capacitor can explode.

remember when some taiwanese manufacturer stole an electrolyte recipe from another company but didnt copy it correctly? a lot of people ended up with leaking or exploding caps on their computers

i think it would be fun to apply a large voltage to a 1 farad 25V cap to see it explode

 
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lol.......

 
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So these larger capacitors don't use a solid insulator, they use a liquid electrolyte? to separate charge?

 
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"The single most important attribute is the capacitance value (expressed
in Farads). Put simply, more is better. Another important
consideration is to make sure the maximum voltage rating of the
capacitor safely exceeds the operating voltage of your vehicle's
electrical system. In addition, ESR and ESL values may be provided
with some capacitors to essentially indicate the amount of voltage drop
that occurs when a capacitor is delivering current. Smaller values are
better in this regard. " http://www.faqs.org/faqs/car-audio/part1/


Simply put, brand name isn't the issue, capacitance it.

 
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as to a noticible performance differnce, you can bet a high esr wont let it respond fast enough. ever hear of a person say their capacitor did nothing to help their dimming? Ill bet the esr was high, assuming it was installed properly and was enough capacitance....

 
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electrolyte of dubilier caps:

"The electrolyte in non-solid electrolyte capacitors is a
biodegradable liquid based on a stable solvent with a high
boiling point as the main ingredient. Common solvents are
ethylene glycol (EG), dimethylformamide (DMF) and gammabutyrolactone
(GBL). The electrolyte includes an acid
base system and other chemicals. The electrolyte is chemically
neutral and contains no PCBs or halogenated compounds."

 
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FYI: caps wont blow up.. they just leak. Transistors on the other hand, wow.. they go POP !

 
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monster caps is the best

 
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dude you must have never seen a cap explode.... try reverse biasing of any cap and exceed its Vf (forward/working voltage) by 100% then youll know what goes pop

 
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make sure its a polarized cap

 
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Every single (electrolytic) cap I have ever seen uses both. See my description of their construction below.

That is not true at all... Caps can go bang in a big way! I have had it happen to me several times and the results are just plain scary.

First and foremost I am considered to be just a little psycho and every year I sacrifice a couple of old caps, transistors and other electronic equipment to show other students how important it is to get things right... Having said that, what I do deliberately, is only a repeat of something I have either done by accident myself or seen done by accident, so don't think that it cannot happen in the real world.

On your average electrolytic cap there are several "safety features" on one end should be rubber, this cap seals the end so that the electrolyte cannot escape. If you have a cap of the "RT" type, that would be the one where there is a lead protruding from each end, then there is probably a small dimple in the rubber, this is to create a weak spot so that if the liquid inside heats up to much and boils the weak spot can rupture and allow the pressure to escape. I have had this happen to me and it was not pretty. Hot, corrosive, probably carcinogenic electrolyte vapour and liquid cannot be good for the person who ends up wearing it... Which was me...

The cap that most people here would be familiar with would be the "RB" type, these are the caps with two leads protruding from the rubber end. Arguably, these are more dangerous, on the metal end of the cap there might be a scribed X shape, as about this is to create a weak spot to allow pressure inside to escape without having the whole thing give way. Again as above should this end rupture you really do not want to be around what comes out...

Should this weak spot not be there (or should it be still strong enough not to give out) pressure built up in this type of cap can cause the entire aluminium case to enter a low Earth orbit, leaving you with a couple of leads and coil of metal film. When this occurs you really do not want to have you head in the way. I have put these cap cases through plaster ceilings and I have seen them crack the plastic boxes in which they were mounted.

The leaking you refer to is also very true, but there are two types of leaking capacitor. The catastophic failures I have mentioned above generally happen in first service, generally from some silly error that you have made like connecting the cap back to front or using a voltage that is too high for the cap. Both types of leaking generally occur with age. The type of leaking I am assuming you are refering to is when the electrolyte begins to leak from around the rubber seal. Generally this happens with age as the seal begins to break down allowing the liquid contents to escape, but it can also be a result of a small scale event like I mentioned above, but there has not been enough pressure built up to actually blow the thing right open.

The other type of leakage in a cap is when the insulation between the plates begins to break down. This lowers the (DC) resistance between the plates from somewhere near infinity to somewhere like a kilo ohm (or in extreme cases, a dead short). Thus instead of looking like a cap across your battery, it looks like a resistor which of course will leak current across it (hence the term "leaky cap"). This is much harder to diagnose than simply looking for a puddle of brown goo!

Now for how your run of the mill electrolytic cap is constructed.

AFAIK all electrolytic caps are of the same basic construction. To make an electrolytic cap, take two sheets of aluminium (I am an Aussie and that's how we spell it) foil lay one out flat and solder a wire to end. Then take some tissue paper type material (ie your solid insulator) and lay this on top. Take the other sheet of aluminium foil and lay this on top of that, again soldering a wire to one end, place another layer of tissue paper on top of this. Now tightly roll the entire thing up and soak it in an electrolyte, which is generally some probably highly toxic, probably carcinogenic, corrosive mixture of oily, gooey, brown gunk. Place the entire thing in a tight fitting aluminium can with a rubber lid to seal it, put on some pretty coloured heat shrink and mark one lead as being negative (exactly which lead needs to be negative I do not know) and voila! One shiny, bright, new electrolytic.