tron07
17-03-2008, 09:24 AM
In most any car, the possiblity of picking up unwanted noises can be reduced if the installation is done properly. Keep the system's wiring away from the vehicle's wiring harness. Attach the ground for the amplifier to a clean, solid portion of the body of frame. Use a good grade of shielded cable for all low level signals.
Because of the astronomical number of possible noise problems, a detailed solution to each and every specific problem is impossible. Here we will discuss the major noise types, and try to proceed from cause to solution of each.
TYPES OF NOISE
1.Alternator noise: This is the most common source of noise, and expresses itself as a high pitched whine which increases and decreases in pitch with the speed of the engine. Unfortunately for sound systems, the cable between the alternator and the battery forms a beautiful antenna to transmit the alternator's noise to anything surrounding it.
2.Ignition noise: Ignition noise is formed by the primary and secondary ignition systems in gas engines. It is characterized by a rapid ticking or popping noise that increases or decreases with engine speed. The first form of ignition noise, from the primary circuit, is caused by the points or solid state circuitry that fires the coil. These primary pulses can feed back through the ignition coil and into the vehicle's electrical system. The secondary ignition circuit is composed of the ignition coil, the spark plug wires, and the spark plugs. Since the secondary circuit operates at quite a high voltage, and since this voltage is pulsed, it forms a nice radio (noise) station under the hood. This noise is often transmitted to the vehicle's wiring harness.
3.Accessory noise: Accessory noise is caused by the electrical noises formed by the many electrical accesssories in the vehicle. The most common noises are the pops caused by high current switches (like the brake light switch) and whirring noises caused by the various electriccal motors in the vehicle (such as the fuel pump or fan motor).
ENTRY METHODS
1. Radiation: Radiated noise is the most common problem found. As mentioned earlier, the worst problem area is the wiring between the alternator and the battery. The entire wiring harness can become contaminated if a portion of it runs along side the alternator to battery cable.
2. Ground loops: Ground loops are the most common way radiated noise gets into a mobile stereo system. This is especially true of multiple amp systems. They have more ground points, and that means more possible locations for ground loops to form. A ground loop is formed when any ground point in the system is at a different potential that at any other ground point in the system.
3. Power Lead (+12V) Noise: Since true power lead noise is the only noise that isn't radiated, and since the vehicle's battery (if in good condition) provides adequate filtering for alternator noise, then only ignition and accessory noise could enter the system through the power leads.
BUILT IN NOISE SUPPRESSION
The vehicle's battery forms a huge capacitor bank that does a fantastic job of filtering noise. Unfortunately, batteries grow old and lose their ability to hold a charge. At the same time, they lose their ability to filter noise, even corrosion on the battery terminals will cause increased noise as it isolates the battery.
If the vehicle is in need of ignition repair or tune up, increased noise will result. Specifically, check the condition of points and condenser, as well as the spark plug leads. Don't forget to check for resistor plugs, too.
TROUBLESHOOTING NOISE
Disclaimer: The following is provided as a GUIDE ONLY, and neither myself, Mycarhifi nor Ozhonda take any responsibility for the outcomes of someone else doing the following. You follow these steps at your own risk!
Once the type of noise has been determined, the entry method must be isolated. The easiest place to start is the amplifier. Unplug the RCA jacks and listen for a change in the noise level. If little or no change occurs, the amplifier's power is contaminated. If the noise is gone, the possibilities are a ground loop or a noise problem earlier in the system. If the problem is a ground loop, the best solution is a better ground for the amp(s). Another solution is to carefully connect a wire from the shield of the RCA connector, at the amplifier end, to a good ground on the vehicle. This will effectively short circuit the ground loop.
The next check is for radiated noise. With the deck still electrically connected to the vehicle, slowly remove it from its installation, and listen for a change in noise level. Any reduction would indicate that noise was being radiated directly into the deck while it was in the dash. If you are dealing with radiated noise, the only solution is isolation. The easiest method is usually to move the contaminated wiring away from the stereo's wiring.
The best way to eliminate power line noise is to install a filter capacitor across the noise source. The best capacitors to use are .5mfd 25v bypass capacitors for the coil, as well as any accessory motors, and .1mfd 100v ceramic disc capacitors for switches. Another way to suppress power line noise is with noise filters.
Courtesy of postings from
http://www.mycarhifi.com/
caraudio forums
Because of the astronomical number of possible noise problems, a detailed solution to each and every specific problem is impossible. Here we will discuss the major noise types, and try to proceed from cause to solution of each.
TYPES OF NOISE
1.Alternator noise: This is the most common source of noise, and expresses itself as a high pitched whine which increases and decreases in pitch with the speed of the engine. Unfortunately for sound systems, the cable between the alternator and the battery forms a beautiful antenna to transmit the alternator's noise to anything surrounding it.
2.Ignition noise: Ignition noise is formed by the primary and secondary ignition systems in gas engines. It is characterized by a rapid ticking or popping noise that increases or decreases with engine speed. The first form of ignition noise, from the primary circuit, is caused by the points or solid state circuitry that fires the coil. These primary pulses can feed back through the ignition coil and into the vehicle's electrical system. The secondary ignition circuit is composed of the ignition coil, the spark plug wires, and the spark plugs. Since the secondary circuit operates at quite a high voltage, and since this voltage is pulsed, it forms a nice radio (noise) station under the hood. This noise is often transmitted to the vehicle's wiring harness.
3.Accessory noise: Accessory noise is caused by the electrical noises formed by the many electrical accesssories in the vehicle. The most common noises are the pops caused by high current switches (like the brake light switch) and whirring noises caused by the various electriccal motors in the vehicle (such as the fuel pump or fan motor).
ENTRY METHODS
1. Radiation: Radiated noise is the most common problem found. As mentioned earlier, the worst problem area is the wiring between the alternator and the battery. The entire wiring harness can become contaminated if a portion of it runs along side the alternator to battery cable.
2. Ground loops: Ground loops are the most common way radiated noise gets into a mobile stereo system. This is especially true of multiple amp systems. They have more ground points, and that means more possible locations for ground loops to form. A ground loop is formed when any ground point in the system is at a different potential that at any other ground point in the system.
3. Power Lead (+12V) Noise: Since true power lead noise is the only noise that isn't radiated, and since the vehicle's battery (if in good condition) provides adequate filtering for alternator noise, then only ignition and accessory noise could enter the system through the power leads.
BUILT IN NOISE SUPPRESSION
The vehicle's battery forms a huge capacitor bank that does a fantastic job of filtering noise. Unfortunately, batteries grow old and lose their ability to hold a charge. At the same time, they lose their ability to filter noise, even corrosion on the battery terminals will cause increased noise as it isolates the battery.
If the vehicle is in need of ignition repair or tune up, increased noise will result. Specifically, check the condition of points and condenser, as well as the spark plug leads. Don't forget to check for resistor plugs, too.
TROUBLESHOOTING NOISE
Disclaimer: The following is provided as a GUIDE ONLY, and neither myself, Mycarhifi nor Ozhonda take any responsibility for the outcomes of someone else doing the following. You follow these steps at your own risk!
Once the type of noise has been determined, the entry method must be isolated. The easiest place to start is the amplifier. Unplug the RCA jacks and listen for a change in the noise level. If little or no change occurs, the amplifier's power is contaminated. If the noise is gone, the possibilities are a ground loop or a noise problem earlier in the system. If the problem is a ground loop, the best solution is a better ground for the amp(s). Another solution is to carefully connect a wire from the shield of the RCA connector, at the amplifier end, to a good ground on the vehicle. This will effectively short circuit the ground loop.
The next check is for radiated noise. With the deck still electrically connected to the vehicle, slowly remove it from its installation, and listen for a change in noise level. Any reduction would indicate that noise was being radiated directly into the deck while it was in the dash. If you are dealing with radiated noise, the only solution is isolation. The easiest method is usually to move the contaminated wiring away from the stereo's wiring.
The best way to eliminate power line noise is to install a filter capacitor across the noise source. The best capacitors to use are .5mfd 25v bypass capacitors for the coil, as well as any accessory motors, and .1mfd 100v ceramic disc capacitors for switches. Another way to suppress power line noise is with noise filters.
Courtesy of postings from
http://www.mycarhifi.com/
caraudio forums