Eliminating Noise in Automotive
Sound Systems

The "beast" you are trying to tame generally takes the form of voltage spikes in the 12 volt power source. These spikes are very short in duration. They are on the order of hundreds of milliseconds to a few microseconds in length, and are repetitive in nature (see paragraph 4 further down in this page). These spikes can also be found in the ground system or in any length of wire that does not have a shielded outer jacket grounded at both of its ends. In very noisy environments, you can even get noise from a small opening the size of a pin head in the case of the amplifying device. This level of noise is not very likely to found in an automotive environment unless you park under a long range radar antenna booming out about 10 megawatts of power. This type of noise is RF (radio frequency) in nature and is transmitted through the air. Both your alternator and ignition system and any electric motor with brushes can emit this type of noise, but in most cases this is not an issue because of the sheilding provided by the metal surrounding the engine compartment. This is the type of noise you are recieving when you hear a CB radio in your stereo in your car or at home.

Getting rid of ignition and other noise from an automotive sound system is sometimes a long and arduous process and somewhat of an art form to be honest. You may have to add filter capacitors in several places to get rid of all the noise in a system. Be patient and be prepared to take some time on this if needed.

First, make sure all the components in your system have good grounds to the chassis of the car. This includes any amplifier, equalizer, radio, or crossover in the system. Assuming this doesn't fix the problem, then add filter caps to the amplifier main power, radio main power and memory power leads, then any equalizer or crossover you may have to add a filter cap to their power lead too. You may need to add a cap to the trigger leads of your various equipment too.

OK, now you've done all this and you still have a problem. Next go to the engine and start adding filter capacitors to all the noise makers in the engine. If you are getting ignition noise, then add a cap to the 12v lead on the ignition coil. This type of noise is generally said to sound like a motor boat type of putt-putt that changes speed with engine speed. If you are getting alternator noise then add one to the output post on the alternator. This type of noise is usually a "whirring" noise that changes pitch as you "rev" the engine.

Be sure to keep all ground leads on your various equipment as short as practical. On a power amplifier this needs to be only about one to one and a half feet in length. When you are adding all those filter caps, be sure to keep their leads as short as possible also. It is no fun when you add a filter cap to get rid of some noise and a long lead on the capacitor picks up noise and adds it back into the system. Also note that when you add your various filter caps, attach them as close as possible to the amplifier, radio, etc. that you are trying to filter. If you filter out all the noise from your power amp, but have a foot of wire between the amplifier and the filter then that length of wire may act like an antenna and reintroduce noise back into the system. This is the same reason you keep your filter capacitor leads as short as possible.

Another way that noise may be introduced into your system is if the wires that supply the power to your amp or its ground are too small in size for the current load of your amp. This problem is especially true of amps but generally is not a problem with radio, equalizers, and crossovers. This also applies to the amplifier ground lead.

It goes without saying that you need to keep all your covers on your equipment so that noise doesn't enter that way. Also it goes without saying that all your RCA lines from the radio to the amp must have a wire braid "shield" in the outer jacket and it is well grounded and if you want to be extra careful, then use a wire with a shielding braid with the ground and signal leads inside and separate from the shield. This type of wire is odd and you may have to do some looking in order to find it, but it will add an extra bit of noise protection if you have a very tough noise problem that you are trying to eliminate.

Well this is all I can tell you about the subject, so I wish you luck. Finding what gets rid of noise in your system is a little like what they say about finding gold, "it's where you find it". Good luck.

	The "beast" you are trying to tame generally takes the form of voltage spikes in the 12 volt power source. These spikes are very short in duration. They are on the order of hundreds of milliseconds to a few microseconds in length, and are repetitive in nature (see paragraph 4 further down in this page). These spikes can also be found in the ground system or in any length of wire that does not have a shielded outer jacket grounded at both of its ends. In very noisy environments, you can even get noise from a small opening the size of a pin head in the case of the amplifying device. This level of noise is not very likely to found in an automotive environment unless you park under a long range radar antenna booming out about 10 megawatts of power. This type of noise is RF (radio frequency) in nature and is transmitted through the air. Both your alternator and ignition system and any electric motor with brushes can emit this type of noise, but in most cases this is not an issue because of the sheilding provided by the metal surrounding the engine compartment. This is the type of noise you are recieving when you hear a CB radio in your stereo in your car or at home.
	Getting rid of ignition and other noise from an automotive sound system is sometimes a long and arduous process and somewhat of an art form to be honest. You may have to add filter capacitors in several places to get rid of all the noise in a system. Be patient and be prepared to take some time on this if needed.
	First, make sure all the components in your system have good grounds to the chassis of the car. This includes any amplifier, equalizer, radio, or crossover in the system. Assuming this doesn't fix the problem, then add filter caps to the amplifier main power, radio main power and memory power leads, then any equalizer or crossover you may have to add a filter cap to their power lead too. You may need to add a cap to the trigger leads of your various equipment too.
	OK, now you've done all this and you still have a problem. Next go to the engine and start adding filter capacitors to all the noise makers in the engine. If you are getting ignition noise, then add a cap to the 12v lead on the ignition coil. This type of noise is generally said to sound like a motor boat type of putt-putt that changes speed with engine speed. If you are getting alternator noise then add one to the output post on the alternator. This type of noise is usually a "whirring" noise that changes pitch as you "rev" the engine.
	Be sure to keep all ground leads on your various equipment as short as practical. On a power amplifier this needs to be only about one to one and a half feet in length. When you are adding all those filter caps, be sure to keep their leads as short as possible also. It is no fun when you add a filter cap to get rid of some noise and a long lead on the capacitor picks up noise and adds it back into the system. Also note that when you add your various filter caps, attach them as close as possible to the amplifier, radio, etc. that you are trying to filter. If you filter out all the noise from your power amp, but have a foot of wire between the amplifier and the filter then that length of wire may act like an antenna and reintroduce noise back into the system. This is the same reason you keep your filter capacitor leads as short as possible.
	Another way that noise may be introduced into your system is if the wires that supply the power to your amp or its ground are too small in size for the current load of your amp. This problem is especially true of amps but generally is not a problem with radio, equalizers, and crossovers. This also applies to the amplifier ground lead.
	It goes without saying that you need to keep all your covers on your equipment so that noise doesn't enter that way. Also it goes without saying that all your RCA lines from the radio to the amp must have a wire braid "shield" in the outer jacket and it is well grounded and if you want to be extra careful, then use a wire with a shielding braid with the ground and signal leads inside and separate from the shield. This type of wire is odd and you may have to do some looking in order to find it, but it will add an extra bit of noise protection if you have a very tough noise problem that you are trying to eliminate.
	Well this is all I can tell you about the subject, so I wish you luck. Finding what gets rid of noise in your system is a little like what they say about finding gold, "it's where you find it". Good luck.

Eliminating Noise in Automotive Sound Systems

Well this is all I can tell you about the subject, so I wish you luck. Finding what gets rid of noise in your system is a little like what they say about finding gold, "it's where you find it". Good luck.

Eliminating Noise in Automotive
Sound Systems