what size / brand capacitor?

[Dave Ladely]

wht size/brand capacitor?

first of all, it is amazing how much power it really does take to reproduce an orchestra, since an orchestra puts out thousands of watts of accoustic energy. Since speakers are known to be about 10% efficient, and amps around 50% efficient, except for digital amps, the actual watts available to the listener is way less than the output of the amps. Again, go to the 3db rule. Seven clicks of the volume controll is about 7 stages of 3db difference, each requiring doubling of power! And seven clicks is not really loud at all. And requires over 1,200 watts when one starts with 10watt background volume. So, lets go a few more clicks on the volume control: next is 2,400 watts, next is 4800 watts, next is 9600 watts, and that is only three more clicks! Then consider the inefficiency problem on top of that. This is why a home stereo can't really reproduce a full orchestra accurately. But with more power the more realism as everyone familiar with home theater is aware: all other things being equal (speakers, etc) more powerful amps will produce an obviously more realistic effect. And some of those effects require a LOT of power. Even my 6000 watts cant quite reproduce some of those effects to a life like degree, though it is impressive. on one occasion, people were here and a railroad train was on tV and it almost seemed to go through the living room. Almost. Impressive none the less.
Large transformers are still in almost all high power home amps. A few have copied Bob Carver's smaller design that uses a tracking circuit to provide power on demand, ,but that tracking circuit is always a mllisecond or so behind the signal and no capacitor solves that problem. Carver's Sunfire amps are fine amps, but most high quality high power or even high quality amplifier manufacturers period, all use good sized power transformers, some very large, hence the weight of the amps. Check out Krell, McIntosh, Levinson, and all the other known quality amps, for example. And they use large capacitors for filtering AC. Sunfire and its imitators are actually an anomaly and viewed by many as compromises to save money and weight, which is true and even Bob Carver will agree, but he will also say he does not beleive that you will be able to hear the slight lag and no one so far has said they could.
If Bob Carver had not built the 700 watt Phase Linear, we would likely not have the power we do have now, since it really was ridiculed at first. The 150 watt amps were very much considered to be more than sufficient. You may not know that, as this was around 1969 that the 700 A came out and was reviewed in Audio Magazine. Now powerful amps are no novelty to say the least. ****, even cars have huge systems, and that is where I start to say it is too much, especially the DB drags, which are ego trips that are juvenile and kind of pathetic. Musical accuracy is the goal, not loudness, loudness alone is pathetic egos crying for ATTENTION.
Evidently some still believe that caps will make up for too low capacity alternators and batteries. I spoke this morning with Bryan Morrison, an electronic designer for the military, and he mentioned the capacitors he has seen with meters, etc., and agreed with my view that the alternator and batteries come first by a long shot. He mentioned that those spending 300 bucks for capacitors would be far better served by putting the money into a high capacity alternator and high capacity battery. The shurett battery, for example, is deep discharge, warranteed for 10 years, should last 15 years.
The electrons from the alternator and battery travel at the same speeds as those in a capacitor, and can supply the current faster than a bass note and will sustain the supply. A capacitor dumps its load before any bass note is complete. A battery filters out any anomalies, and outputs pure DC, since it also acts as a MONSTER cap, as a test with a scope will reveal.
I believe in solving problems at the source, not tacking on some cool looking expensive band aid first. Best to spend the money adding to the alternator's output and adding onto the battery capacity. The 8HD deep cycle in the trunk is a pretty good solution and it is close to the amps so the large cables can be shorter.

 

[Dave Ladely]

capacitor questions, etc

Oh, I didnt say anything negative about big cables, how can I when I use huge marine quality cables for supplying power? But they are not really super expensive. And welding cable works as well if not better as it is very flexible.
Yes, use big cables. But not the hyped up expensive ones. Its a con game!

As for the other cables, the interconnects, that is another con game . The super profit margins sure can get salespeople pushing with all kinds of sales talk that sounds good. Money is incentive for almost anything! Even using irrational gigahertz theory on audio frequencies. American s tend to be insecure, so appealing to our insecurities works well. And PT Barnum said, "No one ever lost a penny underestimating the intelligence of the average American"
So, ply the customer with assurances that the more expensive the cable, the better the sound, even making claims that one should spend X percentage of the total equipment cost on cables, so as to increase the profit margin, and dont forget the tack on warranty to get more dollars out of him/her!!
Of course, cables should be good quality, well made, with good connectors, but cables that are even overkill for audio are still not very expensive. But customers need assurance and they wont get it when money can be made by conning them. The claims being made are bizarre, with subjective paeons that sound like those put out by wineries. Of course, no double blind objective scientific tests are mentioned!!

 

[Shoaz]

The caps after the transformer (when the power supply has a tranformer) a parallel to the supply after it has been rectified from AC to DC, so they're doing the exact same thing in the applications that you're talking about as they are in the auto applications; they're intended to provide short term current supply when the source can't keep up. In the case of an AC input the caps supply the current when the AC is going through zero volts twice per cycle.

For a DC system like in a car, the supply cable will have some inductance and resistance associated with them, and the battery has some output resistance and capacitance as well. This means that they can't change their rate of current supply instantaneously, and when the demand from various devices peaks (for whatever reason, there are all kinds of things that will cause this) the voltage will often droop a little bit as the rate of current increase changes. A capacitor placed locally at the device needing current helps to filter out the transients and provide a local current supply to the device when the source voltage drops or peaks. As you said, it filters the supply to keep it cleaner at the local device.

Very, very few electronic devices DON'T have caps splattered all over their circuit cards just for this task. Most ICs, definitely any amp that you want to have a clean output, will have at LEAST one cap dedicated just to stabilize the current supply for that device. Nowadays most ICs have several of these bypass caps stuck as close to their power pins as possible. The voltage at the ICs own power pin can dip locally to that device due to its own changing current demand, and these "bypass" caps help to stabilize that and keep everything happy.

For amps, where noise on the power supply can affect the output signal, this is even more critical, so there are typically lots of storage and bypass caps stuck on the circuit card very close to the power pins to the device.

You can't put these caps very far from the power pins or they'll lose their effectiveness. Even putting a cap a few inches from the operating device on a circuit card can make it ineffective. So when you say that just getting a good alternator or battery will fix the problem, it won't, because there are too many other devices on the same supply and the distance from the battery means a lot of inductive cabling that will prevent the current at the load from being able to change instantaneously.

The real question, then, as I see it, is just a matter of degree. How much current do you need to hold up an amp that's trying to drive a heavy bass signal? It's not that hard to analyze, and I've never seen even a first-order analysis of how a big of a cap really makes sense. I have a hard time imagining that it needs to be over a Farad (yeah, one Farad), but I haven't done the analysis, either, that's just my personal intuition on a sanity check. There are lots of big amps around that put out a lot of power that don't have supply caps nearly that big, and I've never seen a decent explanation of what's different about car audio that they think they need them.

Caps make perfect sense for the application, almost any electronic device will suck without local storage caps to help hold up the supply voltage, I just don't think they need to be that big. I'm certainy willing to be educated, though.

 

[yamahaSHO]

Eric, I am sure these people are much smarter than the people who make these things...

I had this disagreement with him last year... I'm just sitting back laughing.. I'll go read my Technical Order now....

 

[Shoaz]

Eric, I am sure these people are much smarter than the people who make these things...

The audio world is historically so full of crap it's amazing. It just bugs the daylights out of me when people work hard for their money and some marketing machine takes it from them for no benefit. Grrr.

 

[Dave Ladely]

what capacitors?

Speaking of a good laugh, relying on the people who manufacture these hyped up items for advice on whether their claims are valid is really a great joke!!!
I haven't heard a soul seek the input of a physicist or even an electronic designer. I spoke with Bob Carver , founder of Phase LInear, Carver Corp, and Sunfire, and he also says its hype, but nicely profitable for those promoting such items, as does Bryan Morrison, a physicist whose father was a highly respected engineering professor at the University of Washington, and Bryan also does high frequency and laser design for private industry. I spoke with Bryan about the light dimming problem and he agreed that the lights will continue to dim with a capacitor and that the solution is a high output alternator and a good battery; that any capacitor would be an add on to that and would have neglible benefit.
The proof would be to get the capacitor, with a guaranty that it would be a fix for the dimming lights, and see if it worked, wouldn't it? Gee, a revolutionary thought! Same thing I had to do in the late 60s, build a super amp rather than arm chair theorize about it, then plug it in and see if there was a real difference in the quality and realism of the sound. That's what Bob Carver and I did. I guess almost everybody nowadays knows if there was a real improvement or not. They just don't know how it all started.

 

[autobahnsho]

By the way, there IS some sort of cap in the JBL Sub amp.

I was playing around plugging it in directly to my aftermarket deck and to the key on power line. Even after I turned the car off the amp was giving enough power to the key on line that the deck kept playing for about 10 seconds or so.

I unwired the sub amp power lines and the deck resumed to shutting off with the key off.

I still can't get the subamp to work with the pre-amp outs though...

 

[SHOZ123]

I hardly believe it my self but I agree 99.9% with Dave on this one.

Who ever said they started their car on caps needs a jump start of their own.

 

[yamahaSHO]

I hardly believe it my self but I agree 99.9% with Dave on this one.

Who ever said they started their car on caps needs a jump start of their own.

And why is that.... You don't believe me? You know it all... I know.

 

[SHOZ123]

No I don't know it all. I do know my car will draw over 450A when starting for a few milliseconds. Then settle to 150A. So for the 1 second or so that the car is cranking you need to deliver at least an average of 250As. How many farads is that over a 1 second time period?

 

[Dave Ladely]

capacitor??

A Farad is a measure of capacity, not flow, so your question does not apply.
Kind of like a water tank, how many water droplets (electrons) does it store?
And no way is any real world capacitor going to put out for an entire second.
Have you ever seen a capacitor arc? Its scary! Its like a lightning bolt!!

Capacitance is measured in units called FARADS. A one-farad capacitor stores one coulomb (a unit of charge (Q) equal to 6.28 X 1018 electrons) of charge when a potential of 1 volt is applied across the terminals of the capacitor.
The farad is a very large unit of measurement of capacitance. For convenience, the microfarad (abbreviated F) or the picofarad (abbreviated pF) is used. One (1.0) microfarad is equal to 0.000001 farad or 1 X 10-6 farad, and 1.0 picofarad is equal to 0.000000000001 farad or 1.0 X 10-12 farad. Capacitance is a physical property of the capacitor and does not depend on circuit characteristics of voltage, current, and resistance. A given capacitor always has the same value of capacitance (farads) in one circuit as in any other circuit in which it is connected.
FACTORS AFFECTING THE VALUE OF CAPACITANCE
• The value of capacitance of a capacitor depends on three factors:
• The area of the plates.
• The distance between the plates.
• The dielectric constant of the material between the plates.
PLATE AREA affects the value of capacitance in the same manner that the size of a container affects the amount of water that can be held by the container. A capacitor with the large plate area can store more charges than a capacitor with a small plate area. Simply stated, "the larger the plate area, the larger the capacitance".
The second factor affecting capacitance is the DISTANCE BETWEEN THE PLATES. Electrostatic lines of force are strongest when the charged particles that create them are close together. When the charged particles are moved further apart, the lines of force weaken, and the ability to store a charge decreases.
The third factor affecting capacitance is the DIELECTRIC CONSTANT of the insulating material between the plates of a capacitor. The various insulating materials used as the dielectric in a capacitor differ in their ability to respond to (pass) electrostatic lines of force. A dielectric material, or insulator, is rated as to its ability to respond to electrostatic lines of force in terms of a figure called the DIELECTRIC CONSTANT. A dielectric material with a high dielectric constant is a better insulator than a dielectric material with a low dielectric constant. Dielectric constants for some common materials are given in the following list:
Material Constant
Vacuum 1.0000
Air 1.0006
Paraffin paper 3.5
Glass 5 to 10
Mica 3 to 6
Rubber 2.5 to 35
Wood 2.5 to 8
Glycerine (15?C) 56
Petroleum 2
Pure Water 81
Notice the dielectric constant for a vacuum. Since a vacuum is the standard of reference, it is assigned a constant of one. The dielectric constants of all materials are compared to that of a vacuum. Since the dielectric constant of air has been determined to be approximately the same as that of a vacuum, the dielectric constant of AIR is also considered to be equal to one.
Capacitance varies directly as the dielectric constant and the area of the capacitor plates, and inversely as the distance between the plates.

VOLTAGE RATING OF CAPACITORS
In selecting or substituting a capacitor for use, consideration must be given to (1) the value of capacitance desired and (2) the amount of voltage to be applied across the capacitor. If the voltage applied across the capacitor is too great, the dielectric will break down and arcing will occur between the capacitor plates. When this happens the capacitor becomes a short-circuit and the flow of direct current through it can cause damage to other electronic parts. Each capacitor has a voltage rating (a working voltage) that should not be exceeded.
The working voltage of the capacitor is the maximum voltage that can be steadily applied without danger of breaking down the dielectric. The working voltage depends on the type of material used as the dielectric and on the thickness of the dialectic. (A high-voltage capacitor that has a thick dielectric must have a relatively large plate area in order to have the same capacitance as a similar low-voltage capacitor having a thin dielectric.) The working voltage also depends on the applied frequency because the losses, and the resultant heating effect, increase as the frequency increases.
A capacitor with a voltage rating of 500 volts dc cannot be safely subjected to an alternating voltage or a pulsating direct voltage having an effective value of 500 volts. Since an alternating voltage of 500 volts (rms) has a peak value of 707 volts, a capacitor to which it is applied should have a working voltage of at least 750 volts. In practice, a capacitor should be selected so that its working voltage is at least 50 percent greater than the highest effective voltage to be applied to it.
CAPACITOR LOSSES
Power loss in a capacitor may be attributed to dielectric hysteresis and dielectric leakage. Dielectric hysteresis may be defined as an effect in a dielectric material similar to the hysteresis found in a magnetic material. It is the result of changes in orientation of electron orbits in the dielectric because of the rapid reversals of the polarity of the line voltage. The amount of power loss due to dielectric hysteresis depends upon the type of dielectric used. A vacuum dielectric has the smallest power loss.
Dielectric leakage occurs in a capacitor as the result of LEAKAGE CURRENT through the dielectric. Normally it is assumed that the dielectric will effectively prevent the flow of current through the capacitor. Although the resistance of the dielectric is extremely high, a minute amount of current does flow. Ordinarily this current is so small that for all practical purposes it is ignored. However, if the leakage through the dielectric is abnormally high, there will be a rapid loss of charge and an overheating of the capacitor.
The power loss of a capacitor is determined by loss in the dielectric. If the loss is negligible and the capacitor returns the total charge to the circuit, it is considered to be a perfect capacitor with a power loss of zero.
A battery also stores electrons, so they are somewhat similar. In fact, the Optima battery is built a lot like an electrolytic capacitor!! But a LOT more electrons.
At 450 amps, that is about the current draw of a starter. With an average draw of 150 amps after starting and running, that is still a LOT and I doubt that is accurate. at 12 volts, that is about 1,800 watts. Average?? No stereo I ever heard of, even mine, does not consume 1,800 watts average, more like peak in a few high powered car systems.
I think you will find you have an average current draw of less than 50 amps, but with a stock alternator and small battery, that will dim the headlights at idle and maybe a bit above idle. A 65 amp stock aternator, for example, does not output 65 amps until over 1200 rpm or so. At idle its likely putting out around 15-20 amps. No wonder your lights dim, right? So, with a good high output alternator, say 150 amps capacity, you will be getting about 60 amps at idle. Voila!! no light dimming. Especially if you have a good battery, and expecially if you have a separate battery for your stereo.
Before I retired, I was deeply involved in all phases of stereo and an associate and friend of Bob Carver and others in the very high end home audio field as well as the car stereo field, both in design and also for a time in selling stereos.
Stuart, a friend who lives near Sacramento installed all of the stereos in the several Ferraris owned by the president of Monster Cable. His work on one of those Ferraris was on the cover of Car Stereo mag several years ago.

Start with the foundation of your system for power: big alternator, good battery (big if possible), large power cables (not interconnect cables, those are way different design), and I can assure you your lights will no longer dim. If you get the capacitor, you will find zero change in light dimming of that I am quite sure. check it out with a test.
I am just trying to counter the hype and bs that is rife in this industry, and the customer is vulnerable to being misled, sometimes by the ignorance of salespeople who see proftit, other times deliberately by those who also see profit or are into the philosophy of ego stroking. :****:

 

[Slo-Sho]

Where would one acquire one of these "Big Alternator" from? SHO's have the hard to service mitsu units correct?

 

[SHOZ123]

But doesn't one ampere of current transports one Coulomb of charge per second through the conductor?

 

[Shoaz]

I haven't heard a soul seek the input of a physicist or even an electronic designer.

I'm an MSEE with almost twenty years of design and research experience. I'm not just spouting what I read in a magazine or an internet article somewhere.

The light dimming problem is not what you'd solve with a cap, and is not what the cap is intended for. That's a long-term supply problem that should be solved by more alternator/battery. The cap is to stabilize short-term transients.

Yes, an Ampere is a Coulombs per second. The drain on a cap will depend on the load, and if the load isn't purely resistive (it likely isn't), then it takes some basic calculus to figure out how big of a cap you might need. I'm too lazy (or busy) to do it, and I've not seen it done by anybody else. Some assumptions would need to be made, but it would at least give an idea of how big of a cap makes sense for a particular size of an amp. Perhaps the reason this sort of analysis has never been published is because it'd show that you don't need a cap nearly that big...I dunno.

 

[Dave Ladely]

capacitor

Like the engineer just said, why buy, worry about what does not apply and you don't need just because, as Abraham Lincoln said, "...all of the people can be fooled some of the time...." with fallacies.
Larger capacitors do store more electrons and the American way is the bigger the better automatically. Even if it does no good.

94 and maybe 95 SHOS had an option of having the larger case Motorcraft alternators. May have to get the brackets if yours is small case in those years. Some earlier year SHOs have been converted, with later bracket, belt, and connector, from the expensive but small Mitsubishi alternator. Some have had the Mitsubishi rebuilt to higher output. If you are stuck with the Mitsubishi, which is frustrating but it is not a low output alternator fortunately, then get a deep cycle battery, like th e Optima or a good marine type and put it in the trunk with good cables, and that should solve the headlight diimming and is a good idea anyway, for any stereo. :****:

 

[SHO92]

The light dimming problem is not what you'd solve with a cap, and is not what the cap is intended for. That's a long-term supply problem that should be solved by more alternator/battery. The cap is to stabilize short-term transients.

Eric, most of this discussion has gotten way over my head now, but the reason you stated above, is the #1 reason why caps are bought and sold in the car audio market. This is why I say that caps are a marketing hype more then anything else in this industry. The link I first provided shows that they do work in smoothing out voltage drops, but the question is, is it enough to notice. In the experimenting that I have done and from what I have heard from others, it isn't noticeable. For the $100 that a stereo shop would charge for buying a cap, I'd rather put that money into buying an amp with more output, and be able to keep the gain set lower.

 

[Dave Ladely]

capacitors a hype?

extremely short term transients such as ripple in a power supply. I sold mostly high end stereos for a few years and I was unusual in refusing to hype the customers. I wound up selling more than all the other sales persons combined simply because the customers either knew I was right on or sensed it. In fact, I refused to sell some items. I was never close to being fired due to my sales record.
Rather than a larger amp, though I do love large amps, for the reasons I have cited which are real world considerations, Ithat certainly would not help the light dimming complaint. ISince it is a hassle to change that Mitsubishi alternator, I would get a separate battery for the stereo and mount it in the trunk. Use a marine batter isolator. I really think that would solve your problem. The 90 amp alternator will provide enough power over time to keep the batteries fully charged and the second battery, not connected to the lights, will be able to supply the amps. Your problem is transitory, and your starting battery voltage drops when large currents are demanded all of a sudden. You will notice that, otherwise, your alternator does keep your starter battery charged. That is because the heavy loads are transient and the average power demand is well within your alternator's capacity.

That extra, deep cycle battery along with cables and isolator, will not set you back that much. I would get welding or marine cables. In truth, my cables are way overkill no matter what anyone says. You can use 4 gauge to the trunk to that second battery. You would gain nothing using very heavy cables to charge the battery.
However, the cables between the amps and the battery can be pretty bg, and since your battery is in the trunk near the amps, those cables can be short, which is another advantage. I would also use marine breakers instead of fuses. Sea-Dog is a good brand, check the internet. you can also get a small panel for the breakers on which you can put labels, resulting in a very sanitary, very up-to-date supply system without getting taken on hype.
So, for maybe two hundred bucks, you would vastly improve your power supply sytem and cure your dimming problem where it starts, not a tack on hyped up fraudulent effort to manipulate hope for money.. :****:

 

[Shoaz]

Eric, most of this discussion has gotten way over my head now, but the reason you stated above, is the #1 reason why caps are bought and sold in the car audio market. This is why I say that caps are a marketing hype more then anything else in this industry.

Ok, I think we're on the same page, then.

 

[Dave Ladely]

capacitor?

False, installing a second battery benefits are NOT limited to when the engine is turned off.
While it is true that a second, preferably deep discharge battery is of great benefit with the engine turned off, since you are not discharging the start battery (assuming you have a battery isolator installed, of course), so you can be assured of starting your car after listening to tunes, that is NOT the only benefit.
With a SHO, your alternator is likely about 90 amps max output at cruising rpm. NOT at idle. Alternators don't like to run at full amps, so about a 50% duty is best, making it about 45 amps continuous. Less the draw of your car at night, with lights. With two batteries, you are charging both as you drive, but only the starter battery is hooked to the lights, heater fan, A/C, ignition, etc. When the amp does require a lot of watts, which is not often, that battery and alternator deliver it and the voltage sags and the protective circuit of the amp likely turns the amp off.
But in a two battery system with battery isolator, the second battery is powering only your stereo. So, that battery is not affected by your lights drawing power. And when your stereo requires current, only that battery is delivering the current. So your stereo is isolated from your lights. A 2000 watt amp can deliver a max of about 2000 watts, but very rarely has to and only for milliseconds at a time, say, on a hugh bass note. So, the average running watts is more like 100 watts rms, maybe less, with some peaks which likely don't even reach 2000 watts.
OK, 100 watts rms is about 7 amps rms with about 14 volts. Lets call it 10 amps rms, to be a bit conservative. This is the current the alternator must supply to your second battery to make up for the discharge and maintain a charge. If you hooked up lots of equipment to your system, like watt meters and oscilloscopes, you would likely find this estimate is about right. So, the alternator is charging the starter battery and the second battery, and should be able to do so easily. Meanwhile the second battery has allowed you to isolate the car's system from your stereo and your stereo from your car's system, including the lights. Use short leads from your second battery to your stereo and the battery will supply lots of power very very quickly, can you say "speed of light"? That is how fast the battery can supply current. And a good battery like the Optima, can supply a LOT of current at the speed of light, hundreds of amps for a short time, for minutes. A lot longer time than any capacitor on earth.
So, lets make a bet. 100 bucks if you do install the second battery, a good one, preferably an Optima or similar since its in the trunk, with a battery isolator of course, and fairly large, short cables - and if your lights still dim and your amp turns off, you win. OK?

 

[Venom SHO s7]

Ok, after reading what you guys had to say, I decided to just go with a Red Top battery. It definitely helped, but somehow it didnt take care of the problem completely.
The amp still turns off, but not as often. I was looking at the amp, and it turns completely off, it doesnt go into "protection" mode. Then i was using a cheap current tester ( the kind thats like a screwdriver with a light inside the handle) and noticed that when the amp was off, there was current in the remote wire, but non on the power wire.
Whats weird is that while the amp was off,eventhough there was no current where the power wire goes into the amp, there was current at the power wire between the battery and the main fuse.
This leads me to think that maybe the power wire is being squished or something, but i dont know why that is or if that can even restrict the current flow enough for the amp to turn off.
Im kinda stuck on whats going on, usually by process of elimination im able to find the problem.