How does the sound quality of the sound system always distort?

Distortion is the phenomenon that the input signal and the output signal change in the fluctuation ratio, phase and waveform shape. The distortion of audio power amplifier is divided into two categories: Electrical distortion and distortion. The electrical distortion is caused by the circuit, and the distortion is caused by the loudspeaker. The types of electrical distortion include harmonic distortion, intermodulation distortion and transient distortion. Sound distortion is mainly caused by communication interface distortion. According to the nature, there are nonlinear distortion and linear distortion.

Linear distortion refers to the fluctuation of signal frequency and weight and the change of phase connection, only the fluctuation of waveform and phase distortion occur. This distortion is characterized by no new frequency weight. The nonlinear distortion is the distortion of the signal waveform and the distortion of the new frequency weight. The distortion of audio power amplifier is as follows:

Harmonic distortion

This distortion is caused by the nonlinear elements in the circuit. After the signal passes through these elements, new frequency weights (harmonics) occur. These new frequency weights disturb the original signal. This distortion is characterized by the inconsistency between the waveform of the input signal and the waveform of the output signal, that is, the waveform is distorted.

The main ways to reduce harmonic distortion are:

1, apply appropriate negative reactions.

2, select the expansion equipment with high characteristic frequency, small noise coefficient and good linearity.

3, progressive power storage, improve the power filter function.

Two, intermodulation distortion

Signals of two or more different frequencies differ in beat and form a new frequency weight after passing through an amplifier or loudspeaker. This distortion is usually caused by active devices in the circuit, such as transistors and tubes. The magnitude of the distortion is related to the output power, because the newly occurring frequency weights are not similar to the original signal, so less intermodulation distortion is easily detected by the human ear.

Ways to reduce intermodulation distortion:

1. Select the electronic frequency division method to restrict the operation bandwidth of the amplifier circuit or loudspeaker, and then reduce the occurrence of beat.

2, choose a good tube or circuit structure.

Three. Transient distortion

Transient distortion is an important target in modern acoustics. It reflects the persistent tracking ability of power amplifier circuit to transient jump signal, so it is also called transient response. This distortion makes music lack of level or transparency. There are two forms:

A, transient intermodulation distortion

When an impulsive transient signal is input, because the capacitance in the circuit prevents the output terminal from obtaining the desired output voltage immediately, the negative reaction circuit can not receive a timely response. The amplifier is in an open loop state at this moment, and the output instantaneous overload results in clipping. This clipping distortion is called transient intermodulation distortion. Distortion is more serious on stone machines.

Transient intermodulation distortion (TID) is a dynamic target of power amplifier, which is mainly caused by the deep negative response inside the amplifier. It is the great evil that affects the actual sound quality and leads to "transistor sound" and "metal sound". The main way to reduce this distortion is:

1. Choose good audio equipment and adjust the operating point, as far as possible to improve the amplifier's open-loop gain and open-loop frequency response.

2, we should strengthen the negative reaction of each expansion stage and revoke the negative reaction of the big loop.

Distortion caused by B and low transformation speed

As mentioned above, a high level input pulse causes the chopper to form transient intermodulation distortion. Can low level input pulse cause distortion? This depends on the amplifier's response time, because the amplifier's response time is too long to make the amplifier output signal change can not keep up with the input signal's agile change caused by the transient distortion, known as the transformation rate too low distortion. It reflects the speed of the amplifier's response to the signal. This small distortion amplifier has a good reproducing acoustical resolution, sense of hierarchy and sense of positioning.

Four, communication interface distortion

Communication interface distortion is caused by the reaction of the back EMF of the loudspeaker to the circuit.

The ways of improvement are:

1, reduce the output impedance of the circuit.

2, select suitable loudspeaker to make damping coefficient more reasonable.

3, cut down the internal resistance of the power supply.