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This section describes various problems and concepts which are closely related to electronics.
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The answer to this section was generously provided by David Navone of Autosound 2000. The material in these instructions was adapted from the Autosound 2000 Troubleshooting Flow Chart by Ian Bjorhovde with the permission of Autosound 2000. For more information about Autosound 2000, See section 7. Literature.
This is a set of instructions to debug a stereo installation if there is any noise present after it is completed. Follow each step carefully! If you have more than one amplifier, repeat level one for each amp to be sure that none of them are responsible for the noise.
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This kind of problem is often caused by transients in the signal processor as it powers down finding their way into the signal path, which the amplifier then transmits to the speakers.
Usually this can be solved by adding a little turn-off delay to the processor. This allows the processor to stay powered on for a short time after the amplifiers have powered down, thus preventing the pop.
Many components sold today (such as crossovers, equalizers, etc) have delays built-in. Read your manual to see if it is possible to set this delay on your piece of equipment or be sure to look for this feature during your next car audio purchase.
If your processor does not have this feature, you can build your own delay circuit with a diode and a capacitor. Add a 1N4004 diode in series with the processor's turn-on lead, striped side towards the EQ. Then add a capacitor in parallel, the (+) side of the cap connects to the striped (processor) side of the diode, the (-) side of the cap goes to ground (not the radio or EQ chassis - connect to the car chassis).
Experimenting with the cap value will give you the right amount of delay before the EQ shuts off. You don't want it too long, just long enough to make sure the amp is off before the EQ powers down. 220 - 1000 uF is about right, and make sure the cap is a polarized electrolytic, 16V or higher. Also keep in mind that the diode will introduce a 0.7V drop on the remote wire, which can cause the processor to power down before the rest of the system.
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There is much debate over the benefit of certain wiring schemes (oxygen-free, multistranded, braided, twisted, air core, you name it). However, most people do agree that the most important factor in selecting power wire is to use the proper size. Wire is generally rated in size by American Wire Gauge, abbreviated AWG, or commonly just gauge. To determine the correct wire size for your application, you should first determine the maximum current flow through the cable (looking at the amplifier's fuse is a relatively simple and conservative way to do this). Then determine the length of the cable that your will use, and consult the following chart, taken from the IASCA handbook See section 6.1 What is IASCA, and how do I get involved? [JSC, HK, IDB],
Length of run (in feet) Current 0-4 4-7 7-10 10-13 13-16 16-19 19-22 22-28 0-20A 14 12 12 10 10 8 8 8 20-35A 12 10 8 8 6 6 6 4 35-50A 10 8 8 6 6 4 4 4 50-65A 8 8 6 4 4 4 4 2 65-85A 6 6 4 4 2 2 2 0 85-105A 6 6 4 2 2 2 2 0 105-125A 4 4 4 2 2 0 0 0 125-150A 2 2 2 2 0 0 0 00 |
If aluminum wire is used instead of copper wire, the next larger size (smaller number) should be used. You should also consider the installation demands: will you need to run the wire around corners or through doors or into the engine compartment? These sorts of problems in the car audio application require some special care in cable selection. You will want to have cable that is flexible; it should have thick insulation as well, and not melt at low temperatures. You don't want to install wire that is rigid and prone to cracks and cuts, or else the results could literally be explosive.
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Again, there is much debate over the benefit of the various schemes that are being used by different manufacturers. In general, however, you will probably want to upgrade your speaker wire from the factory ~20 gauge to something bigger when you upgrade your amplifiers and speakers. In most cases, 16 or 18 gauge should be sufficient, with the possible exception of high-power subwoofers. According to an example by Jerry Williamson, using 18 gauge instead of 12 gauge would only result in a power loss of 0.1dB, which is essentially undetectable by humans. Thus, other factors play more important roles in the selection of speaker wire. One issue is that different wires will have different line capacitances, which could cause the wire to act as a low pass filter. Generally, however, the capacitances involved are so small that this is not a significant problem. Be sure to heed the warnings above regarding cable flexibility and insulation, especially when running wire into doors and other areas with an abundance of sharp metal.
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For some components, like head units and equalizers, it's acceptable to use the stock wiring for power. However, amplifiers generally require large amounts of power, and accordingly will draw large amounts of current. The factory wiring in most cars is not designed to handle large amounts of current, and most wires have 10-20A fuses on them. Thus, you will almost always want to run the power line for your amplifier directly to the positive terminal of the battery. This could require drilling a hole through the car's firewall, or at least spending time hunting for an existing hole (the steering column is a good place to start looking). Always remember to place a fuse on your wire as near to the battery as possible! For various reasons, such as an accident or simple wear and tear, your wire's insulation may eventually crack, which could allow the conducting wire to make contact with the chassis of the car and short the battery through this wire, which could lead to a serious fire. The closer you place a fuse to the battery, the more protected you are. Also, when running wire through areas with sharp metal corners, it is a good idea to use rubber grommets to provide extra protection against tearing through your wire's insulation.
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No. In almost every case, the best thing to do is to ground your amplifier to a point that is attached to the chassis of the car and is as close to the amplifier as possible. The ground wire should not need to be more than about eighteen inches long, and should be at least as large as the power wire. The point to which you make your ground connection should be an unpainted piece of bare metal.
Some cars (Audi, Porsche) have galvanized bodies, and in these cars, you must find one of the manufacturers' grounding points or else some noise can result.
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Nothing. This is caused by static buildup by rubbing against the seats, floor mats, etc., just like walking across a carpet in a home. You can avoid this shock by touching something metal on your car before you put your foot on the ground.
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The headlights will dim because of a momentary drop in the voltage level that is available to power the vehicle's accessories, including the headlights, amplifiers, the engine, etc. This voltage drop can be caused by a very large current demand by an accessory, such as an amplifier trying to reproduce a loud bass note.
The first thing to do is to get your battery and alternator checked for proper functioning. A failing battery can place undesirable loads on the alternator, leaving less power for your system.
If the power system appears to be working correctly, an improved alternator may be required for the large current demands of the audio system. When upgrading an alternator, be careful in your purchase, for there are some potential problems. An alternator which advertises a certain output level may only achieve that output at very high engine RPM ranges, for instance. Also, the new alternator must be adjusted to provide an output voltage within a reasonable range in terms of the voltage regulator.
If you find your car will not start after playing the stereo for long periods of time with the engine off, and the present battery is in good working order, then another, paralleled battery could prevent this embarrassing problem.
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Stiffening Capacitor (note capitals) is a trademark of Autosound 2000. However, "stiffening capacitor" (note lowercase), as a generic term, refers to a large capacitor (several thousand microfarads or greater) placed in parallel with an amplifier. The purpose of doing so is to provide a sort of reserve power source from which the amplifier can rapidly draw power when it needs it (such as during a deep bass note). The electrical theory is that when the amplifier attempts to draw a large amount of current, not only will the battery be relatively slow to respond, but the voltage at the amplifier will be a little lower than the voltage at the battery itself (this is called line drop). A capacitor at the amplifier which is charged to the battery voltage will try to stabilize the voltage level at the amplifier, dumping current into the amplifier. Another way to think about it is that a capacitor in parallel with a load acts as a low pass filter See section 3.10 What is a crossover? Why would I need one? [JSC], and the voltage level dropping at the amplifier will appear as an AC waveform superimposed upon a DC "wave". The capacitor, then, will try to filter out this AC wave, leaving the pure DC which the amplifier requires.
The following sections provide more detail about when and why to use a stiffening capacitor.
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Before installation, it's often difficult to predict whether or not a capacitor will be beneficial to you. It's generally best to install the audio equipment prior to making the determination, so that you can address which symptoms need to be remedied and assess the severity of the symptoms. This will not only help you decide whether or not you need a capacitor, but also how much capacitance would be beneficial.
The most common symptom in need of added capacitance is headlight dimming (and sometimes dimming of the interior/dash lights). It's caused by a drop in system voltage associated with excessive current draw. While there may indeed be several loads drawing substantial amounts of current from the electrical system (eg. heat, AC, and so forth), it's usually the transient draws that best manifest themselves in noticeable dimming. This is partly because our visual systems are most sensitive to detecting rapidly changing intensity levels rather than steady absolute differences.
Once you've assessed whether or not the dimming is noticeable (and sufficiently annoying), you must decide whether a capacitor is warranted or if you'd be better served by upgrading the alternator. After initially having your alternator and battery checked out (some places will do this for free), the choice should be based on the severity of the dimming.
A commonly-used estimate for determining the appropriate size capacitor is 1F/kW (one farad per kilowatt). For example, a system running at 300W would need a 0.3F (or 300,000uF) capacitor. However, there are several variables at play here, including the capabilities of the vehicle's electrical system (which generally varies from idle to higher RPMs), the efficiency of the amplifiers, and the listening habits of the user (ie. the tone controls and the type of music). These factors should all be considered when making the determination. Moreover, the voltage drop can be so severe that added capacitance is nothing more than a band-aid. That is, even several Farads of capacitance would not be able to sustain the voltage for as long as the drop persists. This is when an alternator upgrade may be in order.
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Although headlight wiring upgrades can often be beneficial for achieving a higher steady-state illumination, it will not improve the dimming situation. Since the headlights are not the cause of the voltage fluctuations that are producing the dimming, upgrading the wiring will not fix the problem. The voltage fluctuation is present at the battery terminals, so it will be transmitted to the headlights regardless of how the headlights are wired. If you think of the fluctuation as an AC signal, then it becomes readily apparent that this circuit can be represented by an AC signal in a voltage divider. Decreasing the resistance in series with the load by upgrading the headlight wiring actually serves to slightly enhance the AC signal at the headlight's terminals. In other words, the dimming effect could become even worse by upgrading the headlight wiring!
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A common myth in the car audio community is that upgrading the power or ground wire to the amplifier will result in the amplifier drawing less current and therefore decreasing the voltage fluctuation. While the logic is sound, the premise is not. Most amplifiers on the market have semi-regulated supplies which don't maintain a steady power output at a range of supply voltages. This is reflected in the power ratings provided by many manufacturers; some provide ratings for their amplifiers at two different voltages, and the lower voltage almost always causes the amp to deliver less power. In general, the difference in power output tends to correspond well with the supply voltage such that the current draw remains roughly constant (assuming somewhat similar efficiency). Consequently, upgrading the power/ground wiring, which serves to increase the voltage at the amplifier's terminals, will not reduce headlight dimming.
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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.
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If you conclude that your best course of action is to install a capacitor, it should be installed in parallel with the amplifier and, generally speaking, should be wired with approximately the same gauge wire used for a single amplifier (usually 8 ga. is sufficient even for rather large capacitors).
Before permanently installing it, it must be charged. Failure to do so could lead to blown fuses and lots of sparks! Some capacitors come with charging resistors. If yours does not, you can simply buy an automotive bulb and wire it in series with the capacitor's + lead while the capacitor is grounded. The bulb will continue to dim until the capacitor is fully charged. Once the capacitor is charged, it should be treated as you would a car battery; caution must be used to be sure not to short the terminals.
The final step is to permanently install it into the car. There's been much debate about where to install the capacitor. It's been argued that the placement is important because it requires shorter wire lengths. While this is true, there has never been any evidence supporting the notion that it should be installed as close (electrically) to the amplifier as possible. In fact, electrical theory demonstrates that it's more effective at quenching the dimming effects by installing it as close to the device exhibiting the symptom (ie. the headlights) rather than the device that's drawing the bulk of the current (ie. the amplifiers). However, the benefit to doing so is negligible. Therefore, hooking it directly to the battery, the amplifier terminals, or the distribution block are equally valid solutions as long as the mounting location is safe, the wire lengths are reasonably short, and there's an adequate ground present.
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The amplifiers are all connected in one way or another to the battery. In fact, unless you're running separate power wires to each amplifier all the way from the battery, they're usually connected at a more proximal site (a distribution block, for example). The effects of the capacitor are felt by the entire electrical system, including the amplifiers. Therefore, you cannot selectively dedicate a capacitor to a specific amplifier.
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A capacitor serves to smooth the voltage fluctuations associated with transient current draw. As a result, the supply voltage presented to the amp during peak demands tends to be slightly higher than without the capacitor. For most amplifiers, this will increase the power output of the amplifier during transients. The degree to which it increases, however, typically leads to an inaudible improvement.
To illustrate, if you consider an amplifier that delivers 100 watts at 14v and 80 watts at 12v (these numbers are somewhat typical), the difference in output from the speaker will be at best 1 dB when the supply voltage fluctuates from 14v to 12v. However, when you take into account the fact that no practical amount of capacitance can completely eliminate this voltage drop during transients, the difference in output becomes even less pronounced. Further, if you take into account other factors such as loudspeaker power compression (discussed elsewhere in the FAQ), the equivalent series impedance of the capacitor, the length of the transient, and the human's decreased ability to perceive differences in intensity for shorter intervals, this difference in output becomes negligible.
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The battery is most important when the engine is turned off, because it supplies all of power to the audio system. The stock battery in your car may not be up to the task of running a stereo with multiple (or large) amplifiers if it can't supply enough current to the amplifiers. Upgrading your current battery to a larger model may help solve the problem because batteries like the Optima 800 offer a larger number of cold cranking amps.
Generally, adding a second battery is great if you want to listen to your stereo with the car turned off (and be able to start the car again later!). This is accomplished using a dual-battery isolator: a device which allows the second battery to be charged by the alternator, but prevents the amplifiers that are connected to the second battery from drawing any power from the main battery. Installing a second battery may be done instead of upgrading the main battery.
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