Audio Source

Broadly speaking, as long as it can produce sound, it is called a sound source, but the speaker is that any device that can produce sound and convert it into an electrical signal can be called a sound source, such as CD, LP, audio tape, FM / AM broadcast, microphone, etc. are all sound sources, but only the sound source has no way to produce the sound we can hear. The signal must be transmitted through the relevant medium, and the expansion becomes what our ears can hear. To the sound.


What is the pre-stage (pre-amplifier)? The pre-stage is the equipment behind the sound source and before the power amplifier is called the pre-stage. In short, the pre-stage is a "control signal" device, such as EQ, DSP, Line Driver, Electronic crossovers, etc., so all these things must be installed one by one? In fact, it is not necessary, because in fact, there are many front-end functions already included by the host or the back-end. It ’s like some functions on the main unit. I do n’t tell you that you do n’t know it is the pre-level! Like the control interface for selecting CD and TAPE signals. If the car audio main unit does not have a control interface, then you do n’t have to be like a home audio A machine, a machine is moved to the car, and an audio source must be connected to an amplifier, so you will be crazy when you don't have to listen to the audio. Let me introduce a few pre-level functions that are included in the general car audio host:

Volume control or signal control (Volume Select, signal) generally uses a variable resistor that can change the resistance to change the voltage value of the output signal to control the volume (signal). If you do n’t have these control ports, the sound you hear will be at the maximum expansion, then either your device is broken or your ears are broken.

Front-back, left-right balance control (Fader, Balance), its operation method is similar to volume control, only to respond to the difference of the speaker or amplifier, or because of the asymmetrical speaker installation position on the car. Tone sound quality control, the purpose is to make the sound quality can be adjusted and changed according to their own preferences, but this function has been replaced by other additional functions of the current host.

Loudness (loudness gain) When we are listening to music, sometimes at low volume, we can not hear low frequencies like 100Hz or high frequencies. Loudness gain is when we turn on Loudness The frequency band and the higher frequency band make a gain action, which makes you feel that the sound effect is better, but it becomes less flat relative to the full frequency response, and will make you feel treble at high volume. Ears and bass are blurred. These are the pre-level functions that are generally available on general cheap hosts. The next step is to introduce the current pre-level independent sales.

Line Driver (also known as Pully, signal amplifier)

The function of the Line Driver signal amplifier is that the signal is sent to other pre-stage or post-stage signals for amplification gain. At present, the general post-stage (power amplifier, under standard conditions, 1V signal input can reach full open Basically, the Line Driver must at least achieve a low distortion output of 1V), but when considering the large dynamic range, the Line Driver must be added to amplify the signal.

EQ (Equalizer, Equalizer)

The main function of EQ is to compensate for the poor listening environment of the sound, not to allow the influence of sound absorption or reflection, but to make the treble too sharp and the bass too blurry. Generally speaking, the frequency that people can hear is 20Hz ~ 20KHz, and EQ divides this range into many frequency bands, and then adds or attenuates some of the affected frequency bands to achieve better sound effects.

In fact, there are some middle-priced hosts that have already added the above pre-levels. However, due to the inherent shortage of the host, these functions are independent, but some of the higher-priced host groups on the market are almost All the functions are included, maybe we should think about whether these pre-levels still need to exist.


Digital sound processor, this machine is to use digital signals to program control, such as in the opera house, etc., the use of frequency enhancement to reduce the resulting sound field effect, or like turning the song into Jazz, Pop and other music feelings, these are DSP masterpieces.

Electronic crossover

The function of the electronic crossover is used to cut the full-frequency signal to divide the sound. Because the speaker has certain physical characteristics, the small speaker can only produce a higher frequency band, and the large speaker is a lower frequency band, so it must be The splitter is cut and distributed to the amplifier, and then sent to the amplifier and the speaker to produce the sound that suits it.

After stage (Power Amplifier, power amplifier)

The function of the front stage is to amplify the voltage of different signal strength into a voltage of sufficient strength to drive the power amplifier (hereinafter referred to as the amplifier). The function of the amplifier is to amplify the signal amplified by the previous stage with voltage and current, so that the amplifier has enough power to push the speaker. In general, when we choose an amplifier, we must at least meet the following conditions: First, the high signal noise ratio (Sound / Noise RaTIo, S / N ratio), second, it is not easy to distort, and third, it can drive the speaker (this is the most important), 4. High stability, 5. The price is reasonable and meets your requirements.

The classification of amplifiers includes A, B, C, D, G and other amplifiers, which are classified according to his working characteristics, rather than I say that he is a class A is a class A, on car audio I can see about these types A, B, AB, and D. I will briefly describe their advantages and disadvantages. Type A: low distortion, but the efficiency is too low about 20% ~ 30%, easy to overheat, generally low Power amplifier. Class B: easy to distort, about 60% higher efficiency. Class AB: The working characteristics and efficiency are between A and B. Class D: Use Modem (this is not a modem, here is a modulation and demodulation circuit technology) to expand the signal, and then use the arithmetic chip to restore the signal waveform, its efficiency can reach more than 90%, less heat .


The speaker is a decisive device in the audio equipment. Without it, he cannot reproduce the sound you want to listen to. It is also the last and final equipment in the audio. You must understand that the function of the speaker is to convert the electrical signal to the adult ear. The audible sound is about 20Hz-20KHz at a general frequency. However, in the current speaker brands, it is almost impossible to find a speaker that can have a complete, flat and full range. Due to the physical characteristics, it makes the general Speakers with better high-frequency response naturally deteriorate in low-frequency response, and special speaker designs are not limited to this, such as electrostatic speakers, flat speakers, and ribbon speakers. Therefore, in the market, there is a combination of more than one group of speakers. For example, a high tone and a low tone are called two-way, one high, one medium, and one low are called three-way.

It is more difficult for the speakers to show sound quality, timbre and volume in the car than home audio, because the installation position inside is not good, the listening position is even more asymmetric, plus many decorations that cause sound absorption and reflection effects, so Unfavorable factors such as resonance, standing wave, time difference, phase shift, phase difference, etc., so the installation of car audio is a university question.

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