Question: how important is it to install one. would like to get the Pro's and Con's if any Thanks Bobbo

 

Uh oh...you opened Pandora's box...lol. There is alot of speculation about caps on the internet these days. A whole bunch of he said she said. A bunch of tests showing how caps work and bunch more showing how caps don't work. Just to let you know.

Personally I use a cap or caps in all of my system and 95% of my customers systems. I have seen no adverse affects when installing a cap...correctly. I have seen three explode but that was because of incorrect installation. So I am pro caps. Your amp already has a bunch of little ones in it. But a cap is not a repair for a inadequate charging system. You should up grade your factory battery cables, have an alternator that can support the system, and a solid battery. If all those items are up to par then it could be a good idea to use a cap. Ofcourse there is the amount of power you are running to take into consideration also.

 

I have not seen any light dims of any kind. My amp is 100 watts per channel x 4. My son was the one who told me about using a cap. The amps and speakers came out of my honda civic as i installed the equiptment in it and it was a good system and i never had an issue with battery power unless i left it on too long while i was cleaning it for appx 2 hrs . then the battery would drain with the ignition in the acc. mode. so thanks for the info

 

I'm pro-cap too.
Two of my systems have a GAP 15 Farad cap in them.
But..., you will not need a cap for your one amp. GM put a decent altenator in our vettes. Just use 4-guage wire for power and ground. Make sure you get a really good ground. Good luck

 

I've got a diesel with twin batteries and a heavy duty alternator. I've got a 1500w amp and a 250w amp. My fuel pressure bounces everytime the subs hit. Yall think I need a cap? It's been this way for 2 years and I'm still on the stock batteries.

 

With about 1000 watts rms of class a/b power, I need to have a 1 farad cap just to keep my subwoofer amp from shutting off under heavy load. This is with a 105 amp alternator, 2 guage power/ground/big 3 and an AC Delco battery.

Without the cap, after a really heavy bass note the sub amp would shut off momentarily and the lights would dim a lot.

With the cap, no shut-offs and almost no dimming even at full blast.

For the cost, there is really no reason not to install at least a 1 farad cap with any moderately sized stereo. They only cost about 60 bucks for a normal 20v, 24v surge 1 farad 85C cap.

EDIT: You probably won't have the problem with amps shutting off unless you use cheaper amps...the power supplies in my amps aren't exactly up to par, so the cap actually helps them deliver power that they normally wouldn't be able to supply.

 

It sure could not hurt. The general rule of thumb is 1 Farad per 1000 watts rms so you will need a 2 Farads or more.
Running 1750 watts you should have 0-guage wire for power and ground.
Finally, is it just the fuel pressure guage that bounces? If so, I would guess it is the viberation caused by the subs and not a voltage problem.

 

I have seen this thread before. "To cap or not to cap.." I never use a cap and have run multi amp/multi sub systems with 1500 watts with out a cap. I consider them to be an extra load on the system, and are not designed to "fix dimming headlights". If your within the amperage limits of your alternator, have adqeuate power supply to your amps, and have upgraded the big 3, you should be fine.

 

knewblewkorvette, it's gotta be from the electrical draw. Otherwise, my boost gauge would bounce also but it doesn't. Oh well. One more thing to add on my mile long list of stuff to buy. Thanks for the help.

 

From experience...when you exceed the output of the alternator by a small amount, a cap can help quite a bit to stiffen then power supplies of less expensive amps. My amp would literally shut off without the cap connected, and that is with 2 gauge power/ground, big 3 upgrade with 2x 2 gauge per run, and a 105 amp alternator.


Also, I'm sure part of that 1500 watts you were running was class D, which draws so much less current than a/b that it won't effect and electrical system anywhere near as much. My amps alltogether produce about 1100 watts and draw about 130 amps or so at full tilt. A similar system with 1100 watts of class d/h power would only draw 100 amps or so, within the limits of the electrical system on most cars.

 

Here is a little something to think about. If caps do not work, then why are there so many of them built into the amplifier? A cap is designed to do what the alternator and battery can not do. Provided rapid spikes of current. Yes I totally agree that the alternator,battery, and cables should be up to par but to leave the cap out just does not make sense.

 

Randy, this is a good point. Do you think then it has more to do with the amplifier brand? Like, do some makers use more/better caps internally? I can tell you from experience for 3 different class d amps I've worked with on the exact same car (same gauge wire, ground, number of subs, etc)... that there is virtually zero dimming with a JBL1200.1, moderate dimming with an MTX6500D, and massive "not safe to drive at night" dimming with a JL1000/1.

A question was brought up about efficiency. Like a class a/b compared with a class d amp. What is the relationship with sound quality from an a/b amp and the number of caps? I think its interesting that a historically sound quality amp brand like JL builds such an inefficient amp like the JL1000/1 which is a class D. Also, it is important to remember that when bridging an a/b amp, you increase the THD to within the same levels as most class d amps.

WacoKid, will you actually blow a 100 amp fuse with your system at full tilt? You're amp could be shutting down because it is overheating. Unless you blow a fuse, you are not drawing as many amps as the system is capable of.

 

[QUOTE=leolufse]Randy, this is a good point. Do you think then it has more to do with the amplifier brand? Like, do some makers use more/better caps internally? I can tell you from experience for 3 different class d amps I've worked with on the exact same car (same gauge wire, ground, number of subs, etc)... that there is virtually zero dimming with a JBL1200.1, moderate dimming with an MTX6500D, and massive "not safe to drive at night" dimming with a JL1000/1.

A question was brought up about efficiency. Like a class a/b compared with a class d amp. What is the relationship with sound quality from an a/b amp and the number of caps? I think its interesting that a historically sound quality amp brand like JL builds such an inefficient amp like the JL1000/1 which is a class D. Also, it is important to remember that when bridging an a/b amp, you increase the THD to within the same levels as most class d amps. "


Going back 15 years or so ago when I studied this. A class D amplifier has about 80% efficiency. It is a switching amplifier which means the output transistors are either on or off at any given time. A class A/B amplifier is less efficient than a Class D amplifier. It will always have some bias current flowing through the transistor even when there is no audio signal. This is to reduce the crossover distortion of a class B only amplifier. That being said, I don't think the JL1000/1 is an inefficient amp just because your headlights dim when the bass hits. That is more a sign of it drawing a large amount of current. (it may in fact have less on-board capacitance than the other amps you are not seeing the dimming with) Using power doesn't make the amp inefficient, wasting power does. If the power is going to your speaker that's ok. If it is going to heat your amp that is wasting it. In contrast class A amplifiers always have their output transistors fully on, which means they have the lowest distortion rating of all amplifier types. They run very hot because most of the power is not used and is wasted as heat. You won't find many class A amps in the car audio market because of this. Hope this rant clears up your question on efficiency.

Oh yeah, I would say a cap would be a good thing as long as it has a very low ESR. (how much resistance it adds to the path of current flow)

 

Nice! I didn't know all that about the switching capacitors and stuff.

I'm not challenging what you said at all, but I've worked with the JL500/5 too, and that bad boy gets warm, but it is super clean. So it follows then that heat can equal inefficiency and inefficiency would tend to draw more amperage to achieve the same output. Drawing more current means a higher likelyhood of dimming headlights?

The more installs I've done in c5s, the more I'm convinced that its not the alternator or no capacitors that cause the headlights to dim, its the fact that GM used dental floss to wire up the headlights in the first place.

 

Lars the dental floss is true but you have to rember something very important. When a manufacture designs a car they do so with all the included parts in mind and those only. The alternator for instance. If it takes 40amps to properly operate a vechicle then it is going to have a 40 amp alternator. Same with headlights...if they only need 18ga that is all they will get. Try this sometime. Wire a set of headlights directly to the battery using 10ga and a relay...talk about bright. lol.

As far as efficency goes 200Dream is on the money. It takes power to make power. The efficency is a measurement of how that power is used. Either in the form of watts or in the form of heat. A good example is spinning the tires on your car. A car makes 300 rwhp but it spins so bad that only 150 of it make it to the ground. That is inefficient. The car is only getting half the power to the ground. Same with an amp.

 

Well since I don't ever clip my amps for my midbasses or the front speakers, the most I usually pull when going full blast is about 80-90 amps. When I had two amps running the subs I probably pulled around 110-120 amps max. I just have the capability to draw 130 amps, and it sounded like a good number to throw out for an example.

However, I don't think that is the problem with my setup. With the cap disconnected, no matter how long the system has been running (cooling isn't an issue, I have dual cooling fans on each amp) the sub amp will shut off momentarily during heavy beats when pushed hard...I think this is a problem with the power supply in the amp not being very robust. Using the cap fixes this, as well as reducing dimming.

 

Lars,

The JL 500/5 uses more than one type of amplifier in it. The 4 channels for the main speakers are most likely Class A/B and the sub amp is most likely a class D switching amp. I also wasn't saying that an efficient amp will not get hot. I was only stating that heat is a sign of energy being wasted. All amps will give off some heat. The coolest running amp I have ever seen is my Sunfire Cinema Grand amp I use in my home theater. It barely gets warm and has 5X200W of power. Bob Carver needs to start making car audio products.

I have the JL 450/4 and the 500/1 amps and they both run pretty hot so what do I know anyway?

Hey I just bought a 5 farad cap for my system. I want to see if my headlights quit dimming when I crank up the bass. I never really listen to my system loud enough to make the headlights dim while I'm driving it but what the heck. In theory it should even out the current drawn from the alternator during large audio peaks.

Kris