Bad sound quality total distortion? YINSHENG teaches you a few easy moves!
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Linear distortion refers to the change of the amplitude and phase relationship between the frequency components of a signal. Only the amplitude and phase distortion of the waveform occurs. The characteristic of this distortion is that no new frequency components are generated. Non-linear distortion means that the signal waveform has been distorted and new frequency components have been distorted. The distortions produced by audio amplifiers are as follows: 
One, harmonic distortion
This distortion is caused by non-linear elements in the circuit. After the signal passes through these elements, new frequency components (harmonics) are generated. These new frequency components interfere with the original signal. This distortion is characterized by the input signal. The shape of the waveform and the output signal are inconsistent, that is, the waveform has been distorted.
The main methods to reduce harmonic distortion are:
1. Apply a moderate amount of negative feedback.
2. Select amplifiers with high eigenfrequencies, small noise figures and good linearity.
3. Improve the power reserve of the power supply and improve the filtering performance of the power supply.
Second, intermodulation distortion
Two or more signals of different frequencies generate beats and new frequency components after passing through an amplifier or a speaker. Such distortion is usually generated by active devices (such as transistors and tubes) in the circuit. The size of the distortion is related to the output power. Since these newly generated frequency components have no similarity with the original signal, less intermodulation distortion is also easily detected by human ears.
Reduce the method of intermodulation distortion:
1, the use of electronic frequency divider mode, limiting the amplification circuit or speaker operating bandwidth, thereby reducing the beat generation.
2, choose a good linear tube or circuit structure.
Third, transient distortion
Transient distortion is an important indicator of modern acoustics. It reflects the power amplifier circuit's ability to keep track of transient transitions. It is also called transient response. This kind of distortion makes music lack of hierarchy or transparency. There are two manifestations:
A. Transient Intermodulation Distortion When an impulse transient signal is input, the output voltage cannot be obtained immediately due to the capacitance in the circuit, and the negative feedback circuit cannot respond in time. The amplifier is at this moment. The open-loop state causes the output to be overloaded and produce clipping. This clipping distortion is called transient intermodulation distortion. This distortion is more serious on the stone machine.
Transient intermodulation distortion is a dynamic indicator of the power amplifier, which is mainly caused by deep negative feedback inside the power amplifier. It is the culprit that affects the sound quality of the stone machine, causing "transistor sound" and "metal sound." The main methods to reduce this distortion are:
1. Select a good device and adjust the operating point to maximize the amplifier's open-loop gain and open-loop frequency response.
2. Strengthen the negative feedback of each amplification stage and cancel the negative feedback of the large loop.
B. Distortion caused by too low slew rate As mentioned above, high level input pulses cause the amplifier to clip and cause transient intermodulation distortion. So low input pulse will cause distortion? This depends on the response time of the amplifier. Because the response time of the amplifier is too long, the change of the output signal of the amplifier can not keep up with the transient distortion caused by the rapid change of the input signal, which is called the conversion rate too low distortion. It reflects the speed of the amplifier's response to the signal. This small-amplifier amplifier is very good in terms of its resolving power, texture, and orientation.
Fourth, the AC interface is distorted
The AC interface distortion is caused by the back-EMF of the speaker (the potential generated by cutting the magnetic force lines when the speaker sounds vibrating) is fed back to the circuit.
Improvement methods include:
1. Reduce the output impedance of the circuit.
2. Select a suitable speaker to make the damping coefficient more reasonable.
3, reduce the internal resistance of the power supply.