【 Weak current College 】 on audio amplifier distortion of points---Power By 【 China power house network 】

Recently I see 2002 e-Bulletin No. 199-page manual vol.1 in an article entitled: "talk about audio amplifier distortion and common ways to improve the article," think this article is well written, well worth a look, electronics enthusiasts will this article points out, for your reference.
Distortion is the input signal and output signal amplitude proportional relation, relationship and phase change waveform shape. Audio power amplifier distortion into electric distortion and acoustic distortion. Electric distortion is caused by circuit, sound distortion is also caused by the sound device speaker. Electric distortion types: harmonic distortion, intermodulation distortion, transient distortion. Sound distortion primarily exchange interface distortion. By nature, a nonlinear distortion and linear distortion.
Linear distortion is the signal frequency component of the relationship between the amplitude and phase changes, only the amplitude of a wave and phase distortion, this distortion characteristic is not a new frequency component.
Nonlinear distortion is the signal waveform distortion occurs, and produce a new frequency component of distortion. Audio power amplifier distortion of the main points arising were as follows:
First, the harmonic distortion
This distortion is a circuit caused by nonlinear components, signal through these components, has produced a new frequency component (harmonic), these new frequency component on the original signal interference, this distortion characteristic is the input signal waveform and output signal waveform shape is not consistent, i.e. waveform distortion occurred. Reduce the harmonic distortion options are: 1, impose an appropriate amount of negative feedback. 2. choose characteristics in high frequency, small and noise coefficient of linear amplifier. 3. enhance the power of power reserves, improved power supply filter performance.
Second, the intermodulation distortion
Two or more different frequency signal through the amplifier or speaker after beat and constitute a new frequency components, this kind of distortion are often circuits active devices (such as transistors and valves). Distortion of the size and output power, because of the new generation of these frequency components and the original signal no similarity, and therefore fewer intermodulation distortion is also very easy to be aware of the human ear.
Reduction of intermodulation distortion: 1, using electronic crossover, limiting amplifier or speaker of bandwidth, thereby reducing the beat generation. 2. choose the linear good pipe or circuit structure.
Third, transient distortion
Transient acoustic distortion is an important indicator, which reflects the amplifier circuit on transient jump ability to keep track of the signal, also known as transient response. The distortion makes music missing level or transparency, there are two forms:
A, transient intermodulation distortion.
In the enter the pulse of the transient signals, due to the capacitors in the circuit so that the output will not be able to immediately get the recognition they deserve for output voltage, but the negative feedback circuit cannot get timely response, amplifier-opening in this moment in a State that allows output transient overload resulting clipping, the clipping distortion called transient intermodulation distortion, this distortion in the machine on a more serious.
Transient intermodulation distortion is a dynamic power amplifier, mainly by the amplifier internal depth negative feedback. Is machine sound, resulting in the sound of the "transistor" and "metal sound". Reduce the distortion method: 1, choose a good device and adjustment work points to maximize open-loop gain of amplifier and open-loop frequency response. 2. strengthening the zoom level of negative feedback, cancel the negative feedback loop.
B, conversion rate is too low-induced distortion.
Of the above, the high level of input pulse amplifier producing clipping and transient intermodulation distortion. The low level of input pulse is causing distortions? this depends on the amplifier response time, because the amplifier's response time is too long to amplifier output signal changes to keep up with rapid changes in the input signal without distortion, caused by transient is called the conversion rate is too low distortion. It reflects the amplifier on signal reaction speed, the low distortion amplifier, its replay sound analytical ability and sense of depth and orientation are all very good.
IV. communication interface distortion
AC connector distortion by speakers of back-EMF (speaker sound vibration, cutting magnetic lines of EMF)-feedback to the circuit. Improvement methods are: 1. reduced circuit output impedance. 2. choose the right speaker to rationalize the damping coefficient. 3, reduce power internal resistance.