How to hook up a cap for your stereo??? Log Out | Topics | Search | Register | Edit Profile | User List
Last Day | Last Week | Tree View | Moderators | Help/Instructions
WakeWorld Discussion Board » >> Boats, Accessories & Tow Vehicles Archive » Archive through January 14, 2005 » How to hook up a cap for your stereo??? « Previous Next »
By Nate (norcalmalibu) on Monday, September 27, 2004 - 7:06 pm:    Edit Post Delete Post
I just recently got a cap for my stereo and Im wondering how I hook it up. Do I run it from the battery to the cap then the amp? I think thats the correct way? thanks

By mike singer (clubmyke) on Monday, September 27, 2004 - 9:40 pm:    Edit Post Delete Post
yes... and keep the cap close to the amp...

also yo will need a resistor to charge the cap.. DONT JUST HOOK UP THE UNCHARGED CAP TO THE BATTERY, it is a good way to start a fire.

By Nate (norcalmalibu) on Monday, September 27, 2004 - 10:01 pm:    Edit Post Delete Post
Were do I get a Resistor for the cap? This might sound dumb but can I hook up a battery charger to it? thanks

By mike singer (clubmyke) on Tuesday, September 28, 2004 - 2:33 am:    Edit Post Delete Post
one should have come with the cap,some have a little light bulb. they are kind of small.

btw, when you charge the cap, disconnect it from the amp.....

i would suspect a car charger would work but i am not sure. i would check with the manufacture.

By adam Curtis (acurtis_ttu) on Tuesday, September 28, 2004 - 6:05 am:    Edit Post Delete Post
resistor should come with the cap. Its ver simple and the cap will charge instantly.
By Grant West (whitechocolate) on Tuesday, September 28, 2004 - 6:36 am:    Edit Post Delete Post
Charge the cap. Start a fire? Is that what they told you at the stereo store.

Thats B.S

By Tom Barnard (tlb) on Tuesday, September 28, 2004 - 6:48 am:    Edit Post Delete Post
My understanding was the little light bulb drains the cap so it won't spark when you touch the leads to it.
By adam Curtis (acurtis_ttu) on Tuesday, September 28, 2004 - 7:21 am:    Edit Post Delete Post
Your supposed to charge and drain the cap. I've not done this and nothing happened. Make sure you disconnect the power and groudn from the main battery.
By Nate (norcalmalibu) on Tuesday, September 28, 2004 - 11:11 am:    Edit Post Delete Post
Well I got the cap used, so basiclly all it is a cap that is 1.5 farad and has a digital read out. The only thing that I heard was that it will drain your battery? So does anyone know if I can just hook up a battery charger to it? thanks

By adam Curtis (acurtis_ttu) on Tuesday, September 28, 2004 - 1:36 pm:    Edit Post Delete Post
How would a cap won't drain your battery. All the cap does is store power. It doesn't use any power. It acts like a battery in the way it stores power but can discarge and recharge instantly. Surf around on here and the net on what a cap does. Some people will argue that caps are a waste of money unless you get into the 15-20 farad ones. I've alwyas used them and feel it does put less of a strain on a boats battery's. I wouldn't use them in my truck. I keep my battery's on a trickle charge most of the time. My stock altenator has a hard time keeping up w/ the demands of my system.
By Nate (norcalmalibu) on Tuesday, September 28, 2004 - 11:32 pm:    Edit Post Delete Post
Thanks adam for the info, sounds like I can just hook it up. I usualy trickle charge my batteries after each use anyways dont want to get stuck with a dead battery.
By mike (clubmyke) on Wednesday, September 29, 2004 - 10:38 pm:    Edit Post Delete Post
here is a link that explains how to charge a cap..

hope that helps,


By Tommy (laptom) on Thursday, September 30, 2004 - 4:28 am:    Edit Post Delete Post
It's smart to charge the cap. And to charge it with a resistor (otherwise the loads can be way to high). If you put an unloaded cap on your system and connect it to the battery, the cap will load it self in a couple of msec. Therefor put a hugh load for a couple of mseconds on your wires. Put it's mostly no peoblem.
Also, a cap WILL drain your battery. It stores your power, but like every cap it also loses power. But this drain is marginal (a bit more then the battery itself).

By Rod McInnis (rodmcinnis) on Thursday, September 30, 2004 - 1:10 pm:    Edit Post Delete Post
Regarding the capacitor draining the battery: Capacitor leak. Big capacitors tend to be very leaky. For daily use the leakage wouldn't be enough to worry about, but for winter storage it can become an issue.

You can get a fairly reasonable estimate of the leakage by charging the capacitor up and letting it sit for a while, then measuring how much the voltage has dropped. The basic equation for a capacitor is i=C*dv/dt (which means the current equals the Capacitance times the change in volts divided by the change in time).

A one farad capacitor that is transfering one amp will change one volt in one second. So if you have a 1 farad capacitor, charge the capacitor up to 12.5 volts, let it sit for one hour (3600) seconds, and then discover that the voltage is 11.5 volts, you will know that that the current = 1*(1/3600) = .00028 amps. You can ignore that, it would take 20 years to discharge the battery.

On the other hand, if the voltage drops one volt in ten seconds, then the current = 1/10, which will seriously discharge your battery in about 3 weeks.

Regarding the charging of the cap:

If you are going to be concerned about "charging" the cap, then you will also need to be concerned about it every time you shut the battery switch off or disconnect the battery leads. The voltage will drop some on the cap just because of leakage, but it will probably drop a LOT because it will then be supplying current to the entire boat! When you go to connect up the battery lead again there will be a very large current rush to the cap.

By Rod Rinnert (deltahoosier) on Thursday, September 30, 2004 - 2:06 pm:    Edit Post Delete Post
What makes you think you need a cap? All the cap is for is inductance in your wiring. If you put a resistor on your cap you are taking away the whole reason for the cap most likely. The cap is there to supply extra juice if your wiring can not supply it in time. It helps with the transit response of your system. If you need a cap you most likely have a different issue like too small of wires feeding your amps.
By Rod Rinnert (deltahoosier) on Thursday, September 30, 2004 - 2:07 pm:    Edit Post Delete Post
Part of the reason for a LED on the cap is a fansy way of keeping you from killing yourself. A big cap has a lot of stored energy and can be very dangerous.
By 882001 (882001) on Thursday, September 30, 2004 - 2:37 pm:    Edit Post Delete Post
i agree with rod i would say loose the cap and go with the "big 3"
By Geoff Maus (bluemalibu) on Friday, October 01, 2004 - 10:40 am:    Edit Post Delete Post
It is proper to “charge” a capacitor (cap) prior to hooking it up to it’s normal power source. Many caps come with a resistor just for this. The resistor limits the inrush of current into the cap. This reduces / eliminates arcing when the normal power is hooked up to the cap. Arcing can wreak havoc with sensitive electronic components, so it is best to avoid it if possible.
If your cap did not come with a resistor, you can charge it using a 12 volt test light. Have the ground side hooked up normally. Hook the test light clip to a 12 volt source. Touch the test light probe to the positive side of the cap. The test light will light up, and slowly dim as the cap comes up to charged voltage. The light dims because as the cap charges, the voltage in the cap matches the battery voltage. After charging, hook up your power to the cap normally.
You can use the same test light to discharge your cap. With the power lead disconnected, hook your test light to the negative side of the cap. Touch the probe to the positive side of the cap. The light will be bright, and slowly fade as the cap discharges.
I run a 1 farad cap in my stereo system and I do this every time I hook up my battery banks.

Rod McInnis,
Of course your calculations are correct for determining Ah draw. The problem most of us have is that the meter used will most likely draw a much higher draw than the capacitor. Even my Fluke 98 cannot measure delta V in a 1 farad capacitor without inducing more delta V than the capacitor is producing itself.
You are 100% correct in that you need to charge the cap every time it is hooked up.

Rod Rinnert,
You asked a great question, “do you need a cap?”
I don’t know what Nate is running for a stereo system, but for those of us who run systems with large sub amps, the answer could be yes.
I run three 12” subs powered by two dedicated sub amps at well over 1000 watts RMS – just for the subs. In my own testing, I hooked up a Fluke meter to “capture and record” the voltage my sub amp sees. Playing a bass heavy song, as the bass would hit, I could “watch” the drop below 10 volts, measured at the amps.
I frequent “Sound Domain” and other stereo web sites, and fully understand the “big three”. I am running “OO” wire from my battery bank to a distribution block less than 12” from my amps. My ground side is equal.
For my system, I needed to add a capacitor to give my subs the instantaneous power they need to work properly. By adding a 1 farad cap, my instantaneous voltage drop at the amps is less than .2 volts – a big change that you can hear in the system.

For a small sound system, a cap is probably not worth the hassle. For a big system, they can be a useful tool to improve sound quality and performance.


By Nate (norcalmalibu) on Friday, October 01, 2004 - 11:32 am:    Edit Post Delete Post
Thanks alot Geoff your information has been extreamly helpfull. Im going to use a test light to charge the cap. My system is going to be around 1500-2000 watts I wonder if using a cap is going to pay off? thanks again

By Rod McInnis (rodmcinnis) on Monday, October 04, 2004 - 11:11 am:    Edit Post Delete Post

A Fluke multimeter should have a 10 megohm input, which at 12 volts would draw 0.0000012 amps, or about 1/1000th of a current that would be interesting. You can ignore it, or better yet, leave the meter disconnected and check every ten minutes or so.

The need for a cap will depend largely on the amp. A well designed amp would be able to tolerate significant voltage drops without any degradation in output. A cheap amp might suffer if the voltage drops too much. Adding a cap to an amp that doesn't need it won't do anything for you.


By Rod Rinnert (deltahoosier) on Monday, October 04, 2004 - 11:23 am:    Edit Post Delete Post
Richard Clark did not like them and argued heavily against them. I remember some had posted the link to the article.
By Geoff Maus (bluemalibu) on Tuesday, October 05, 2004 - 11:55 am:    Edit Post Delete Post
Rod McInnis,
You are one of the most technically informed people who post on this site, and I have a lot of respect for your input. That said, I have performed tests on my own stereo capacitor using a Fluke 98 and another digital multi meter. In my testing, the internal resistance of the meters I tried was much higher than the internal resistance of the capacitor. You can prove this to yourself by hooking a meter up to a charged capacitor and watching the voltage drop. Measure the delta V for one minute. Recharge the capacitor to the same starting voltage and let it sit for an hour then check the voltage. The voltage drop in the unconnected capacitor will have dropped much less in an hour than the voltage drop shown in one minute when hooked up to the meter. In my testing, in the second test, the voltage began to drop as soon as I hooked up the meter.
In conclusion, in my own testing, my Fluke 98 meter and my OTC multi meter both had much more internal resistance than the capacitor. Does this mean that the capacitor does not have internal resistance? No, we know that they do. In my test, I found that it was pretty small in comparison to the internal resistance of the multimeter – which is small.

I also run quality amps – MTX and JL. Maybe not what Grant–White chocolate would run, but still decent quality stuff. After running my system with and without a cap, I found that the capacitor does indeed provide a noticeable improvement in the “hit” of the bass in my system.


By Rod Rinnert (deltahoosier) on Tuesday, October 05, 2004 - 2:20 pm:    Edit Post Delete Post
The fluke meter has to have a high internal resistance or you will draw current through it. It is in the tech specs. You can not make accurate voltage measurments if you are dropping voltage across the voltage meter. Caps have to have a low internal resistance inorder to function the way they are designed. Higher resistance increases your RC constant and would delay the discharge.

Actually, your test proves just the opposite. Measure the delta V for one minute. Recharge the capacitor to the same starting voltage and let it sit for an hour then check the voltage. The voltage drop in the unconnected capacitor will have dropped much less in an hour than the voltage drop shown in one minute when hooked up to the meter.

That says to me the internal resistance of the cap is much greater than that of the multimeter, since the cap has not discharged as much as having the multimeter connected.

Regardless, the test is not a funtional one in that it only is testing shunt resistance.

By Rod Rinnert (deltahoosier) on Tuesday, October 05, 2004 - 2:30 pm:    Edit Post Delete Post
Also, in reference to a cap that has a resistor...
I think the reason for the resistor on the caps might be a shunt resistor to help discharge the caps. These caps are of a pretty good size and if you short the leads with it charged, you have the potential to explode it. I think it is not to help it charge slow, but, to be able to sell these to the general public and not get someone hurt.

By Geoff Maus (bluemalibu) on Tuesday, October 05, 2004 - 4:25 pm:    Edit Post Delete Post
Rod Rinnert,
You are correct, I should have written that the Fluke meter has a higher internal conductance than the tested capacitor. Your conclusion that the test compares resistance validates the intent of the test - that in this case, the Fluke meter caused a faster delta V than the capacitor alone.

Here is an interesting note from the Monster cable web site:

Monster Cap™ 1.0 Farad Stiffening Capacitor™

Low ESR allows large amount of current transfer in a very short period of time, without voltage drop.

Detects voltage drop from battery across any load for improved current capacity of your 12 volt system.

Greatly improved transient power response, bass impact and definition.

24k hard gold contact terminals for maximum conductivity and corrosion resistance.

Developed by car audio specialists Richard Clark and David Navone exclusively for Monster Cable®.

Separately available optional longer capacitor screws for use with CPRT Power Rings.

If the cut and paste does not show up completely, it is at:

It looks like Richard Clark developed this capacitor.

“Richard Clark did not like them and argued heavily against them” Hmmmm
Is this the same Richard Clark?

Also, from the instruction sheet that came with my capacitor,
"WARNING This capacitor must first be CHARGED witht he resistor supplied"
The resistor can be used to charge and to discharge the capacitor. Shorting a large capacitor could be dangerous. quality stereo system caps have a "anti-pressure" vent to reduce the chance of violent case rupture, if shorted.


By Mike H (seaswirlmike) on Tuesday, October 05, 2004 - 8:08 pm:    Edit Post Delete Post
So i'm not to familiar with caps but all the talk about how to hook one up and the advantages of one made me look into them and i have a question that i would think is very basic compared to how much you guys seem to know about caps.
I was looking on e-bay and sounddomain and noticed a lot of caps are rated 16Vdc, 20Vdc, 24Vdc... Can you use any of these on a 12v system like in a boat or do you need to actually be running 16, 20, or 24Vdc for them to work? Or can i just add one to my system?


By Rod McInnis (rodmcinnis) on Wednesday, October 06, 2004 - 1:24 pm:    Edit Post Delete Post
I have a rather low opinion of Monster products. They are much more hype than they are substance. I have been very disappointed with the few Monster products that I bought.

Just the marketing hype that you cut and pasted includes a good example: "Detects voltage drop from battery across any load ..." . Exactly what does that mean? It is a capacitor, it doesn't "detect" anything.

Regarding the need for the cap, it will all depend on the design of the amp. Consider, for a moment, ohms law and your speaker. Have you considered how you get a 12 volt system to deliver 1000 watts into a 2 ohm speaker?

The basic equation for power, in terms of voltage and impedance, is P=V**2/Z (Z is the impedance of the speaker, and lower is better). So, if the actual final stage of the amplifier is operated off of 12 volts the best you could do is (12*12)/2 = 72 watts. Not very impressive.

If you want a 1000 watts you will need to drive a 2 ohm speaker with 45 volts or more. If you want to drive a four ohm speaker at 1000 watts you need to apply 63 volts to the terminals. So how, you might ask, do you do that from a 12 volt system?

The amp has a power supply that boosts 12 volts to a higher voltage. When the bass goes BOOM the power supply has to really kick into gear to keep up. If the power supply chokes if the input voltage drops to 10 volts then a large cap might help. On the other hand, if the power supply has some operating margin and can keep on working down to 6 volts or so then it doesn't need the cap.

There are certainly some amps/installations that will benifit from adding a cap. But don't be surprised if you add the cap and don't notice any difference.

The voltage rating of the cap is the maximum voltage that they can safely withstand. Exceeding the voltage rating of a cap is very, very bad! Exceeding the voltage, even for an instant can cause an arc inside the cap and an internal short. In my electronics career I have had capacitors short while I was working on the system, and it can get exciting! And these were caps that were only a fraction of the size we are talking about.

Your boat has a "12" volt system, but the actual operating voltage with the engine running and the battery fully charged will be 14.2 volts. It is not unusual for there to be brief surges above that, and a failure in the alternator regulator can easily cause voltage exceeding 16 volts. Thus, I would not recommend a 16 volt cap.

It is always safe to use a higher voltage rating cap. The only disadvantages will be that it will be physically larger and cost more.

By Mike H (seaswirlmike) on Wednesday, October 06, 2004 - 1:37 pm:    Edit Post Delete Post
we'll right on that cleared it up for me....

thank rod

By Rod Rinnert (deltahoosier) on Wednesday, October 06, 2004 - 4:30 pm:    Edit Post Delete Post
Try this:

Here is another thread with Richard Clark involved:;f=1;t=020321;p=5

I am still looking for the exact lesson Richard Clark gave. Maybe Grant has it?

By Rod McInnis (rodmcinnis) on Thursday, October 07, 2004 - 11:01 am:    Edit Post Delete Post
Rod Rinnert:

In that first link you posted they do a very nice job trying to compare the effects of the price of tea in China on how your stereo is going to sound. It doesn't matter to you what the voltage is at the input of the amp, what matters is the quality of the signal the amp drives out to the speakers.

In the second link you can observe Richard Clark arguing with others about several topics, mainly focused on Richard's viewpoint that you will never hear any improvment from a cap. Richard argues that the amp should have a regulated power supply (which is basically what I was saying above) and that unless the input voltage drops below the "dropout" point the amp will produce the same output regardless of what the 12 volt input is doing.

There was a counter argument that some amps use an unregulated power supply. Such a supply would take the 12 volts and raise it some fixed ratio. Say the ratio was 4:1, then if your input was 14 volts then the output would be 56 volts. If the input voltage sagged to 11 volts then the output would drop to 44 volts. This "might" impact the output signal. In this case, a big enough cap might help.

By Geoff Maus (bluemalibu) on Thursday, October 07, 2004 - 12:15 pm:    Edit Post Delete Post
Rod McInnis,
Another insightful reply, thank you.
The last thing I am going to do is jump up to defend Monster products. The reason I referenced them was because Rod Rinnert had mentioned Richard Clark. At one time, Richard Clark designed Caps for Monster. That was my only point. Okay, I will defend Monster in that I have had some decent luck with some of their higher end shielded RCA cables in the past.

Now, on to the more important part of our discussion.
Your discussion into power in watts from an amplifier to a 2 ohm speaker was interesting and informative, but it is off point. This thread is centered on the supply side current to the amplifier.
When we talk about energy supply, we need to think about two things, voltage and current. In our boats, as we turn up the volume in our stereo systems, the amplifiers are not looking for higher voltage, they are demanding more current. Voltage drop is often times a symptom of an inadequate supply of current. In my own stereo system, I can measure the current flow from my batteries to my stereo power distribution block – using a Fluke clip on current meter. At a very low volume, the stereo may draw only a few amps. When I turn it up, the current draw skyrockets, I have measured over 175 amps flowing into my stereo system. My point is that when turned up, my subwoofer amps showed signs that they were starving for power during heavy bass sections. When I added a capacitor to my system, there was a noticeable audible improvement. When I tried to determine why there was a difference, I performed tests using the best tools I own, I could “see” a more constant voltage at the sub amplifiers. My testing led me to believe that the capacitor is linked to a more consistent feed of power to my amplifier and in my system, that led to improved sound quality and performance.

As you mentioned, and as I have mentioned in the past, some systems may benefit by adding a cap, some may not. I am one of those people who has benefited. When we look at the total cost of a decent stereo system, the cost of a cap is tiny. If you understand what a cap can do for your system, and are realistic about it, it could be worth a try.

Rod Rinnert,
Excellent link, I could only access the caraudiolounge link though. I have studied similar tests in the past, some show a cap will make an improvement, other tests show no improvement. Things I never see enough information on is exactly what products are actually being tested (meaning isolated from other variables), what is the power supply, is it allowed to deviate, are the products “off the shelf” products – or manufactures “specials”, where are the test inputs being taken from, if other changes are made, how would they effect the test, Etc.
That is why I tend to do my own tests, and try to make sense of what works for me.

Back to the subject of capacitors, it seems rare to see a competition car audio system (SPL) that did not incorporate capacitors – Unless they were in a class that did not allow them.

My reference to Richard Clark was more to make a point that even some of the so called “experts” play both sides of the fence.


By Rod Rinnert (deltahoosier) on Thursday, October 07, 2004 - 12:42 pm:    Edit Post Delete Post
Instead of clicking the second link. Try to cut and paste it. It will link you into a the middle of a discussion and you can to fowards and backward in the discussion. About 7 pages worth.

I understand about playing both ends against the middle, but, Richard Clark has a Cool $5,000 that you can not tell the difference if your system is designed right. He has a challenge to people to prove otherwise. The crux I got out of the arguing in the thread I linked too, is if you need a cap:

a) you either have poor wiring
b) you have cheap/ poor designed amps
c) and it does not matter anyway because the output stage caps in your amplifier would already have to be charged to help the sound and with the time delay in an amp, it does not matter what you do on the input feed at that time you need the juice. Then that would point back to a and b in my very simplified synopsis of the arguments in the thread.

It is quite an informative thread.

By Geoff Maus (bluemalibu) on Thursday, October 07, 2004 - 2:57 pm:    Edit Post Delete Post
Rob Rinnert,
Thanks for the heads up on the "cut and paste" on the Carsound thread. Another great thread with lots of pro and con. I could not find a clear convincing argument for or against a cap.

You could add "d" to your list where we use our amps in an environment that allows us to push them beyound what the manufacturer had originally anticipated.
If I thought longer, I could probably come up with a "e" and "f" and "g".

If Nate, the person who started this thread, does try one, it will be interesting to hear his opinion.


By Rod McInnis (rodmcinnis) on Friday, October 08, 2004 - 12:48 pm:    Edit Post Delete Post

The purpose of my discussion regarding the power into a speaker was to illustrate that it is impossible to get that kind of power driving an amilifier with 12 volts. To get more than 72 watts into a speaker the amp MUST include some sort of power supply to convert the incoming voltate to something much higher than 12 volts.

Since they have to design a power supply to boost 12 volts to 63 volts, they might as well design one that can boost 8 volts to 63 volts and then there won't be any issues.

By Geoff Maus (bluemalibu) on Friday, October 08, 2004 - 1:43 pm:    Edit Post Delete Post
Rod McInnis,
Point well made, and well taken.
Your point makes my last post even more important – regarding the relationship between voltage and current. As the voltage is allowed to drop, current must increase – to keep the same power output. As current flow increases, so does heat and other issues.
Would it not be better to provide the amp with proper voltage and current, and not allow the issue of voltage drop to come up at all?


By Rod McInnis (rodmcinnis) on Saturday, October 09, 2004 - 11:29 pm:    Edit Post Delete Post
It would be best to provide the amp with adequate wiring so that there wasn't a voltage drop due to the wire!


Topics | Last Day | Last Week | Tree View | Search | User List | Help/Instructions Administration
Privacy Policy | Terms of Use
WakeSpace is owned by eWake, Inc.
Copyright © 1996 - 2008, All Rights Reserved.