Why Class A amplifier sound quality is good - A class amplifier sound quality good reason analysis

Class A power amplifier with Class B amplifier compared to why the sense of better than Class B amplifier it?

In the static, a class amplifier and Class B power amplifier connected to the pure resistance load, the test may be almost the same indicators, or even a large number of thermal noise. But the actual application, then the real load (dynamic load) - the speaker, and different frequencies when the speaker impedance is not the same, then the integrated electro-acoustic indicators will be inferior to the pure resistance load when the indicators, resulting in transient distortion. Since the presence of negative feedback is fed back to the previous stage, the key to this transient distortion is that the speaker system quality off design is effectively and uninterrupted due to damping (control), and the higher the voltage rise rate of the signal The more serious the distortion. For high fidelity, it is important that the mass inertia of the loudspeaker system be effectively damped (controlled) by the loudspeaker.


Class B amplifier damping can not effectively control the speaker, for any half of the week only one arm output at work, or push or pull, but can not work at the same time, so its damping is unidirectional, that is, whether positive or negative half week, he only Produce the power to promote the speaker work, and can not produce the control back to the pull, to all-round damping, drive current must be timely for the problem here.

In the case of input square wave, the input signal may be more complicated than the square wave when the input is possible. When the signal rises, the speaker can work according to the signal waveform, but when the signal suddenly stops, the speaker does not stop immediately because of the inertia of the mass , At this time its voice coil to produce back-EMF caused by the conduction of the A-arm output tube anti-bias and cut off, and the original in the cut-off B arm is turned on, while the back-EMF again by the negative feedback back to the front level is amplified Thus encouraging the B-arm output tube to accelerate conduction, together to complete the B class amplifier this special damping, because this process to zero, there is a moment to lose damping free oscillation. This process is completed, B arm conduction variable cut off, the original conduction was reverse bias A arm output tube to restore conduction, but also experienced a zero zero loss of damping moment to restore damping. So that the damping of Class B power amplifier in any moment are unidirectional, the damping of the speaker is by repeated zero-zero commutation to achieve, almost always produce distortion.

Class A amplifier is both positive and negative arms are connected, the damping coefficient of the two directions, in the sudden high voltage rise, the voice coil in accordance with the waveform to action, the signal stops, the resistance of the B-arm through the conduction path, inertia Damped, can not produce free oscillation, the back electromotive force can not be established, a class of amplifier that omni-directional damping, forcing the Yan change dynasty converter vibration is always based on the signal waveform to vibration. This is like a motorcycle is expected, said go away, said stop to stop.

From the above analysis, you can understand the quality of a class amplifier sound moving.