1. Noise usually invades your sound system through the following channels:
A, the power cord invasion (through the host and power amplifier power cord into the system).
B. Current through ground wire (through antenna ground wire and power amplifier ground wire).
C interference from other wires (interference from antenna reception and original vehicle lines)
Interference from other electrical appliances (electric horn, generator, etc.). ).
Note: Items A, B and C are related.
Second, the response to car audio noise countermeasures
The components commonly used to deal with noise are automobile audio capacitor (especially effective for dealing with high-frequency noise), current coil (inductor), filter, grounding wire and so on. , to deal with the noise generated by the ignition system.
1. Check whether the positive pole of the ignition coil is installed on the capacitor. If the capacity is reduced, the platinum contact will be easily ablated, resulting in interference sparks. It is necessary to replace the nonpolar capacitor with a capacitance of 0,5UF/400 V, and check whether the carbon wire is used in the ignition high-voltage line. If the metal wire is used, it is easy to cause interference, and the radio part has serious interference and must be replaced. Spark noise can be suppressed by increasing the local resistance of the resistor. The method is to connect 1 megohm resistor in series in the main high voltage line output by the ignition coil to reduce interference.
2, eliminate motor noise
First, the equipment and signal lines modified for car audio are far away from the motor and motor line. 1 nonpolar capacitors can be connected in parallel at both ends of the motor, or two inductors can be connected in series at the positive and negative wires of the motor respectively, and then the two nonpolar capacitors are connected at the positive and negative wires of the motor respectively, and the other end is grounded to form a filter circuit, which is used to absorb the spark of the motor carbon brush and reduce the noise.
3. There are the following methods to eliminate the noise generated by the relay-free electric horn:
A the terminal of a horn is grounded and connected with a capacitor.
B. Connect an inductor in series on the terminal of a horn, and then connect a capacitor in parallel to ground.
C, respectively using the method on the terminals of two loudspeakers.
D connect a capacitor in parallel between the horn button contacts of the steering wheel.
4. There are several ways to eliminate the noise generated by the relay electric horn.
A, electric horn bracket and the body should be in good contact.
B, connect a capacitor in parallel at both ends of the relay contact, or connect a capacitor in parallel at both ends of the contact respectively for grounding.
5, poor grounding will produce noise.
If the hood is not firmly grounded, the whole hood will become an antenna, radiating the noise generated by various parts of the car to the surrounding space and introducing it into the sound system from the antenna and various circuits. When installing the connecting wire between the hood and the car body, the paint, oil stain and dirt at the connection must be thoroughly removed.
There should be a good connection between the engine and the car body, or between the front wheel suspension and the car body, and between the exhaust pipe and the car body.
6. Power line noise suppression:
In order to effectively eliminate the noise generated by the power line, a power amplifier near the current loop should be installed. If there are multiple power amplifiers, a loop should be installed near each power amplifier, because noise can be transmitted from one power amplifier to another, making a single loop ineffective.
7, signal line (RCA) incoming noise suppression:
The signal wire should be far away from the power wire and installed on both sides of the car body to avoid the possibility of interference. If the signal wire has a double-layer shielding net, the outer shielding net should be connected to the bushing.
There will be many problems in practical application, but it is important to find the interference source first, and then solve it with the right medicine, so that every program played by the car audio system is clear, pure and perfect.
Noise problem is the most common and the most difficult to eliminate in car audio fault, because the structure and wiring of the car are complicated and there are many places where noise is easy to occur, so you need to master some knowledge of car circuit and car audio to troubleshoot the fault easily.
Troubleshooting: First, according to the noise situation, find out the fault location through principle analysis and judgment, and then adopt different troubleshooting methods.
Simple elimination method: first, listen to the radio, tape and CD parts of the stereo for noise. If there is noise, check whether the power cord, ground wire and signal wire are reasonable, whether the signal wire is loose and whether the grounding is disconnected. The power amplifier shall be insulated from the vehicle body. According to different noise sources, different measures should be taken to deal with it. If the noise cannot be eliminated, the noise source should be treated, and then noise prevention measures should be taken to completely solve the noise.
Third, the best tuning method of car stereo
Automobile audio debugging plays a very important role in the development of automobile audio products. Just like a gun, if the sight is not accurate by the school team, the bullet must be biased. Let's learn how to debug the car stereo according to the introduction of an audio master.
Preparatory work:
1) First, restore all the additional functions of the automobile main engine to the factory state, and then center all the high, medium and low sounds, of course, the left and right balance is the same.
2) Set the volume (gain) of the power amplifier at the lowest position (minimum).
3) The filter is set to OFF.
4) Cross is set to the lowest.
5) The subwoofer power amplifier is also handled in this way.
Step 1: host debugging
Turn on the mainframe, play some high-fidelity vocal discs or discs with strong bass, and turn the volume to half or three fifths. This will make it easier for the bass to combine with the mid-bass in the front sound field, and it will be easier to produce the full bass.
Step 2: debug the front sound field
Let's increase the gain of CHANNEL- 1/2 until the sound is loud or the maximum sound you can accept. Then we will turn down the volume of the mainframe, put in a vocal disc or a disc with a stronger low frequency, and then slowly turn up the volume of the mainframe until it is slightly louder than you normally listen to. Well, at this time, you should listen carefully. Is the voice clear? Is there a nasal sound? Or a deep voice? If the sound is clear without nasal sound, or the low frequency is very elastic, there is no trailing "buzzing" sound, and there is no fog at the low frequency, congratulations, your front door sound insulation and shock absorption installation is basically perfect. In this state, your front door bass will play its best role.
Step 3: Debug the host
Usually, when the volume of the host increases, there will be nasal sounds, just like catching a cold or feeling unclear pronunciation. If there is a low frequency, there will be a "buzzing" tail sound. These conditions are called * * * vibration, which affects the clarity of sound. * * * Vibration will counteract many details of sound, slow down the low frequency of sound, and make your 5W audio equipment become 1W sound.
So what can be done to eliminate the vibration? Sound insulation and shock absorption is a means. In addition, we can reduce the probability of this sound by dividing the frequency (cut-off frequency) on the host or power amplifier. Let's look at the picture again. You can try to set the filter setting to HP (Qualcomm) position, and set the frequency dividing knob to 60 Hz, 70 Hz, 80 Hz, 90 Hz or even 100HZ. Filter (cutoff frequency) and frequency division (cutoff frequency) are used in combination. The adjustment of frequency division (cutoff frequency) is effective only when the filter (filter setting) is in LP or HP state. In the case of unclear sound, we try to rotate the CROSSOVER (cut-off frequency) to see if the nasal sound of human voice disappears or there is no "buzzing" sound at low frequency when it is twisted to that position. If it is at 60.
Step 4: Tune the rear sound field.
No matter what the state of the front sound field is, the rear sound field should be set in HP state, and the frequency division (cutoff frequency) should be adjusted to about 150HZ. At this time, the volume of the host should be turned up, and the gain of the power amplifier should be turned up to the normal high volume. The sound coming from the front seat to the rear sound field is correct. If you can hear it, it means the sound is too loud.
Step 5: Bass adjustment
The adjustment of bass is a key to car audio, which will make great changes to the sound. It's best for two people to debug the bass together, one in the car and the other in the back. After the first four debugging steps are completed, set the power amplifier filter (filter setting) for pushing bass to LP (low pass) position, twist the frequency division (cut-off frequency) to the lowest, then twist the gain to half or three-quarters of the front sound field, then twist the host volume to the normal high position, and put in the disc with strong low frequency. If the bass is too much or fuzzy, it is that the gain is too high. Adjust the gain of the bass quickly.
Don't worry, remember the following points:
1, properly set the frequency divider function of equalizer or power amplifier after installation;
2. Adjust all the volume (including the host, equalizer and power amplifier) to zero, check whether all the working power indicator lights are lit normally after startup, and turn on part of the volume of all power amplifiers after everything is started normally;
3. Play music at a slight volume of 1/5 for 5 minutes;
4. Play at the volume of 1/4 for 5 minutes;
5. Finally, play the music at the volume of 1/2 for 5 minutes.
The above-mentioned volume playing action is to make the host, power amplifier and speaker (split speaker and subwoofer) in the system adapt to the input and output of different volumes (one pot) first, and then protect the material to play at high volume as soon as it makes sound, which directly causes the speaker coil to burn out or the instantaneous stroke is too large, resulting in internal injuries such as bottoming out, and even burning out the power amplifier.
6. After the initial play, if everything is normal, start the standard adaptation step (and then explain it according to the standard adaptation step above).