# Is a capacitor really necessary-Yes or no, and why or why not



## coomaster1 (Jul 22, 2010)

I'm looking to find a definitive answer to weather or not you need a capacitor in your system.,or is it just a band-aid for something else that should have been done in the first place. Thanks


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## qwertydude (Dec 22, 2008)

You don't need them. I've installed them and the only thing they stop is dimming on really quick transients like kick drums. They don't really store enough energy to prevent dimming on sustained bass notes.

You're better off doing the big three and running good heavy gauge wire. Then after that getting a good AGM battery like a Yellow Top.


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## robert_wrath (Apr 24, 2011)

Why bother with Stiffening Capacitors while you may invest the funds into an AGM battery and/or High Output Alternator?


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## nrubenstein (Sep 4, 2008)

Also, HID headlamps will not dim due to voltage drop.


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## Victor_inox (Apr 27, 2012)

nrubenstein said:


> Also, HID headlamps will not dim due to voltage drop.


Unless it drops to like 9 volts, but then you`ll face much more serious problems.


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## Oliver (Jun 25, 2007)

Commonly used as a band-aid or magic wand [ after-the-fact ].


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## robert_wrath (Apr 24, 2011)

Funny issue about caps, they're installed incorrectly over 95-98% of the time.


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## MarkZ (Dec 5, 2005)

coomaster1 said:


> I'm looking to find a definitive answer to weather or not you need a capacitor in your system.,or is it just a band-aid for something else that should have been done in the first place. Thanks


You will NOT find a definitive answer, because your question is far too vague to answer definitively. I hate to rain on your parade. 

I urge you to read some of the other threads that have discussed the use of capacitors. You'll find a variety of answers, and you're going to have to sort through those answers to decide whether it's useful for your own particular situation.


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## Thunderplains (Sep 6, 2009)

Also, just to note, that in the realm of the class "D" amps, which are many, they really don't matter at all with class "D". Only thing I ever did was upgrade to an optima yellow top and I ran 3 high power zed amps without so much as a blimp power wise. Caps are old school


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## wooferdog (Mar 31, 2011)

caps don't help much at all and if your wiring is not up to where it should be, as in the big 3,ho alt,good battery its a waste of space.


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## MarkZ (Dec 5, 2005)

MarkZ said:


> I urge you to read some of the other threads that have discussed the use of capacitors. You'll find a variety of answers, and you're going to have to sort through those answers to decide whether it's useful for your own particular situation.


For example, this 6 year old thread might be worth a read.

http://www.diymobileaudio.com/forum...-actually-worked-anyone-want-explain-how.html

It gets pretty technical as it goes on, so you probably don't have to go far past the first page, but it's a thread that examines WHY adding a capacitor can sometimes reduce headlight dimming. It explains some of the conditions where it might be beneficial, and some where it won't be. So you can kind of decide whether your plans are well-suited for your goals...


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## 24th-Alchemist (Jun 16, 2011)

To my mind the "capacitor issue" serves as a microcosm for the way this forum tends to operate at large: different people have various surface-level observations, and then they ascribe to their observations *unverified* explanations.

I think this is probably true:


> Funny issue about caps, they're installed incorrectly over 95-98% of the time.


What does that imply about the impression most users will have about the effectiveness of caps?

For example, the idea that


> You're better off doing the big three and running good heavy gauge wire


 seems to me to be a necessary prerequisite for effective cap operation, not an alternative.

Has anyone on this forum ever gone to their car and measured any variables pertinent to cap operation? (For the record I have).

Most of the commentary about caps for car audio on internet forums is recycled misinformation posted by people who have an incomplete understanding of how caps work and who have never measured anything related to a cap in a car and who could probably not effectively measure the appropriate variables anyway.

Good luck finding an answer. I would be interested to hear from someone who knows what they're talking about, but I for one am not going to hold my breath.


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## Justin Zazzi (May 28, 2012)

please stop discussing capacitors

again


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## robert_wrath (Apr 24, 2011)

If you must install a cap inline with your amplifier(s), I suggest following this:


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## BumpaD_Z28 (Dec 12, 2011)

robert_wrath said:


> If you must install a cap inline with your amplifier(s), I suggest following this:


I'm for sure not a safety freak, but some safety glasses would have made me feel A LOT better about that video !

~DaVe


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## MarkZ (Dec 5, 2005)

cajunner said:


> visual effects, like less amplifier-induced current starving showing up as a steadier headlight beam is not really the intended purpose, if there is no audio benefit.
> 
> Because, just because the lights dim a little, doesn't mean the amplifier power supply isn't able to compensate, and if there is compensation then no audio benefit can be heard. You will want to hear one, though.


You're overthinking things! Sometimes people just want the dimming to go away because it's annoying. Has nothing to do with audibility.


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## sqshoestring (Jun 19, 2007)

They are not necessary at all. Caps can help in some situations, mostly where you are on the edge of what your car's alternator can provide and you don't flog bass music on your system. If you have massive amps in your car and the stock alt is not getting it on, caps will do nothing for you because you don't have enough power.


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## Pitmaster (Feb 16, 2010)

sqshoestring said:


> They are not necessary at all. Caps can help in some situations, mostly where you are on the edge of what your car's alternator can provide and you don't flog bass music on your system. If you have massive amps in your car and the stock alt is not getting it on, caps will do nothing for you because you don't have enough power.


I ran a 25 farad hybrid capacitor (don't know the true capacity.) Seemed to work ok on my 3 amp set-up, and it had cool blue neon lights and a built in amp meter. But my volt meter was all over the place at higher volumes.
I'm now running a aux alt, and a AGM battery on the same set-up with much more stable VM readings, and no headlight dimming!
I have seen You Tube testimonials on a capacitors undisputed usefulness in power condtioning, and could be included in the system.
In the end, I'm sold on a proper charging system, instead of an after thought.


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## MarkZ (Dec 5, 2005)

Not me.  I think if your car starts in the morning, your charging system is fine.

Having said that, I can understand why people want to increase their system voltage with an aftermarket alternator. It's usually not the financially wise thing to do, but some people are married to certain amps for various reasons and don't want to upgrade them. Higher voltages usually mean you eek out a few more watts, which may not be audible but nevertheless it makes the user feel better.

The problem is that there are a ton of HO alternators that still do poorly at low RPMs, so I'm not convinced they're the catch-all that people make them out to be.

Personally, I don't think the electrical system matters very much most of the time. There's a disproportionate amount of money and energy that people expend in it. I think most people would be better off putting that money into amplification, and spending their time on things that matter, like system design, measurement, and signal processing.


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## qwertydude (Dec 22, 2008)

Pitmaster said:


> I ran a 25 farad hybrid capacitor (don't know the true capacity.) Seemed to work ok on my 3 amp set-up, and it had cool blue neon lights and a built in amp meter. But my volt meter was all over the place at higher volumes.
> I'm now running a aux alt, and a AGM battery on the same set-up with much more stable VM readings, and no headlight dimming!
> I have seen You Tube testimonials on a capacitors undisputed usefulness in power condtioning, and could be included in the system.
> In the end, I'm sold on a proper charging system, instead of an after thought.


When people start talking about power conditioning my BS flags start going up because of all the HiFi nonsense that power conditioners and special power cords seem to attract. So much bogus testing that claims they make music more musical TV pictures more three dimensional.

Any good amplifier will a reject the fair amount of noise that can the power conditioners claim to filter. And I suppose if you really want the capacitor to do the best at amplifier voltage smoothing, take your amp apart and connect that big cap directly on the circuit board where the main filtering caps are.

If you're electrical system is so noisy and unstable that a cap needs to be installed I'd say fix that first rather than install the capacitor.


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## MarkZ (Dec 5, 2005)

qwertydude said:


> When people start talking about power conditioning my BS flags start going up because of all the HiFi nonsense that power conditioners and special power cords seem to attract. So much bogus testing that claims they make music more musical TV pictures more three dimensional.
> 
> Any good amplifier will a reject the fair amount of noise that can the power conditioners claim to filter. And I suppose if you really want the capacitor to do the best at amplifier voltage smoothing, take your amp apart and connect that big cap directly on the circuit board where the main filtering caps are.
> 
> If you're electrical system is so noisy and unstable that a cap needs to be installed I'd say fix that first rather than install the capacitor.


Yup. And re: noise, let me just add that what happens on the primary side of the transformer doesn't really matter that much.

The best place to defeat power supply noise is actually on the other side of the transformer. That's where the signal comes in direct contact with the power supply, and where PSRR is usually determined. This is mostly a product of the circuit topology, grounding strategy, etc. In other words, it's amplifier dependent. So if you're screwing around adding caps to try to defeat some noise problem, then maybe you should reconsider why you're using the particular amp. [or, more likely, re-evaluate the rest of your install, because ground loops are responsible for noise the vast majority of time]


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## MP1472 (Oct 2, 2012)

MarkZ said:


> Not me.  I think if your car starts in the morning, your charging system is fine.
> 
> Having said that, I can understand why people want to increase their system voltage with an aftermarket alternator. It's usually not the financially wise thing to do, but some people are married to certain amps for various reasons and don't want to upgrade them. Higher voltages usually mean you eek out a few more watts, which may not be audible but nevertheless it makes the user feel better.
> 
> ...


this makes me laugh seeing as i just went through this.. So I have a 180 amp alternator built by dc engineering it amounts to about $550 shipped with 0 guage upgraded alt wiring

i pay another 80 to put it in then i get way worse headlight dimming driving or at idle plus now my hd 1200 shuts down at any kind of higher volumes so i have some volt meters thrown on it its dipping into the 10's so i figure alt is bad i pay another 80to take it out then ship it back to dc they test it and say its fine.

i go round and round with them how can it be fine when i get worse dimming than stock i have my amps shutting off on me how is this fine? Stock alt is 80 amps.

Long story short my $700 ho alternator is sitting in a box in my garage


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## Pitmaster (Feb 16, 2010)

MarkZ said:


> Not me.  I think if your car starts in the morning, your charging system is fine.
> 
> Having said that, I can understand why people want to increase their system voltage with an aftermarket alternator. It's usually not the financially wise thing to do, but some people are married to certain amps for various reasons and don't want to upgrade them. Higher voltages usually mean you eek out a few more watts, which may not be audible but nevertheless it makes the user feel better.
> 
> ...


I agree that HO alternators aren't all they're cracked up to be, that was my reason for a seperate dedicated 100 amp alt single pole alt that puts out max voltage just off idle. It cost $125 plus $20 for the longer belt, and I installed it with some custom brackets, and a Stinger AGM battery (which is widely accepted to be a necessary upgrade).
Now I have a solid foundation for whatever HU, processors or amps I add later, at just a fraction of the cost of my total existing system.
To boot, the original factory charging system remains entact and seperate , and the car starts fine every morning.


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## IDGAF (Dec 27, 2009)

FWIW.. capacitors are all they're cracked up to be. And more. The ones that 99.999% of people use just aren't big enough. That's all. 

I compete in SPL and use caps exclusively. No batts at all. Well, to be more specific, they're "super" caps or "ultra" caps. They're 2,600 farads each. Yes... twenty six hundred farads. I run up to 6,000w on (2) banks of them. They're 2.5v cells so I have to series them to get the proper voltage so the cpacity drops to ~ 430F per bank, but that's still waaaaay more capacity than the ones normally used.

I'm actually using them in a daily app right now. I run ~ 4k daily and I'd be hard pressed to get my voltage below 14v. I would really, really have to try. And other than (2) banks of super caps, my electrical is all OEM.

For reference...


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