The sound quality of Class AB amplifiers and Class D amplifiers cannot be simply generalized. There are significant differences in their design principles, distortion characteristics, and listening experience, and they are greatly influenced by specific technical levels and calibration. It is necessary to analyze them in combination with the scene and design level.

I，Core differences and sound quality characteristics:
1. Class AB power amplifier (Linear power amplifier)
    ① Principle: By directly amplifying the analog signal, the transistor operates in the linear region (with a conduction time ranging from 180° to 360°), and the distortion mainly comes from the harmonic distortion during the linear amplification process (which is usually low).
   ② Sound quality characteristics:
    A well-designed AB class power amplifier offers a delicate and natural midrange performance, smooth dynamic transitions, and distortion types that are closer to the "acceptable" harmonic distortion of the human ear (such as even harmonics), providing a warm and soft listening experience. It has a significant advantage especially in music dominated by midrange, such as vocals and string instruments.
    ③ Disadvantages: However, due to the limitations of linear amplification, the efficiency is relatively low (50%-70%), and it generates significant heat at high power, requiring a larger heat dissipation design. The most annoying thing is that it is very difficult to introduce full DSP control.

2. Class D power amplifier (Digital power amplifier)

    ① Principle: The audio signal is converted into a high-frequency pulse signal through pulse width modulation (PWM) (amplification in switch state), and then restored to an analog signal through low-pass filtering. It has extremely high efficiency (usually 80%-95%), generates little heat and is small in size.
    ② Sound quality characteristics:
    Early D-class power amplifiers, due to insufficient PWM modulation accuracy and simple filter design, might introduce switching distortion, high-frequency noise or a "digital flavor" (harsh sound and missing details), especially in high-frequency and dynamic performance, they were not as good as AB-class ones.
    However, modern high-end D-class (such as those using higher-frequency PWM, precise filtering, and feedback compensation technologies) have significantly improved distortion, effectively suppressed switching noise, and the distortion index (THD+N) can be as low as below 0.001%. The listening experience is close to that of excellent AB-class, and it even has an advantage in transient response (due to the fast switching speed).
    Traditional perception: Due to the inherent advantage of linear amplification, Class AB power amplifiers are regarded as having "more natural sound quality and a more delicate listening experience" in mid-to-high-end Hi-Fi and home audio scenarios, and are considered the "sound quality first" choice. Due to the early technical limitations, Class D was often associated with "low cost an

    ③ Current situation: Technological progress has narrowed the gap between the two. The sound quality of high-end D-class amplifiers can now compete with that of excellent AB-class ones, and in some scenarios (such as those requiring high-power, small-sized active speakers and car audio systems), they are even more practical.

    ④ A greater advantage is that it can be fully controlled by DSP from start to finish (from small signal to power output), including the final frequency division output. This type of power amplifier is called a dsp power amplifier. It has 26 adjustable indicators, supports Bluetooth 5.0 and above versions, and is powered by 12v. Supports 6 channels, 8 channels, and 14 channels of output, with each channel delivering 200,000 watts. It's sufficient for general household use.
    The final sound quality depends on the design level of the specific product: a low-quality AB class may not be as good as a high-quality D class, and the difference between a top-quality AB class and a top-quality D class is more reflected in the listening style (such as warmth vs. precision), rather than being absolutely "good or bad".
    If compared at the same level, the author believes that DSP power amplifiers are superior.