It is not uncommon for a racing car with a highly optimized and high-performance engine to affect performance due to unacceptable wheels and tires. In this case, the engine must work harder to compensate for wheel and tire defects, and the performance of the entire system of the car will be affected.
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The same is true for amplifier selection for high performance audio and drive speakers. For many years, people have chosen AB amplifiers as amplifiers for high definition (HD) audio. Audio Class D amplifiers are considered unacceptable because they do not meet all the requirements for HD audio. But this situation has changed.
High-definition or high-resolution audio refers to audio with a sound quality of more than 16 bits (more than the sound quality of a laser disc) and a sampling rate greater than 44.1 kHz, as shown in Figure 1.
Figure 1: Dynamic range and bandwidth of some audio formats
In HD audio, the digital front end includes a digital signal processor with a 32-bit audio data path, an audio sample rate of no less than 96 kHz, and an integrated 24-bit ultra-low noise digital-to-analog converter (DAC). Higher digits improve signal-to-noise ratio (SNR) and dynamic range (DR), providing better resolution (>97dB), allowing very small sounds to be heard and not distorted. The faster sampling rate enables higher bandwidths (sampling rate/2) above the human ear's hearing range (>22 kHz) and encodes more sound information for accurate reproduction.
The audio amplifier that drives the speakers is located at the digital back end where audio performance and security can be achieved and evaluated. The system includes some sound enhancement and sound compensation processing algorithms (such as equalization algorithm, dynamic range control, sound field spatial positioning and 3D effects). But even with all of this processing power, audio amplifiers that complement these capabilities must meet specific HD audio specifications, including:
SNR SNR and DR > 97dB.
Ÿ Total harmonic distortion + noise (THD+N) < -80dB.
带宽 Bandwidth (BW) > 22kHz.
The combination of these high-definition audio amplifiers produces a system that works in harmony so that digital engineers don't have to manually run large processing algorithms to compensate for the lack of audio amplifiers. After all, high-performance analog amplifiers do not have good digital alternatives. In fact, high-performance analog amplifiers can achieve the same or even higher performance with smaller/simpler/cheaper digital engines.
The previous generation of Class D amplifiers achieved 0.03% (-70dB) total harmonic distortion + noise, compared to 0.005% (-86dB) for total harmonic distortion of Class AB amplifiers with similar output power. 2 is shown. Figure 3 shows the same comparison, but it uses TI's latest high-power Class D amplifier. Previously, while Class D amplifiers were about 1.5 times more efficient at high power levels, they did not require much heat dissipation compared to similar power Class AB amplifiers, but for high definition audio, Class D amplifiers were not considered.
Figure 2: High Power Class AB Total Harmonic Distortion and Power Performance Comparison
Figure 3: TPA3251D2 Total Harmonic Distortion + Noise and Power Performance Comparison
TI's latest generation of high-power Class D amplifiers enhance the overall performance and efficiency of high-definition audio systems by creating a symbiotic relationship with the digital engine and efficiently transmitting enhanced audio quality to the speakers. The TPA3251D2 and its companion devices offer 0.002% (-94dB) total harmonic distortion + noise, 100dB signal-to-noise ratio and 100kHz bandwidth while delivering more than 70W of output power. The series is compatible with systems with ultra-low noise and audio sampling rates up to 192kHz. In addition, built-in protection features make it safe to drive HD audio.
The TIDA-00874 shown in Figure 4 shows the symbiotic and harmonious relationship between the TPA3251D2 and the high-definition system digital engine. If you want to design with a Class D amplifier, TI's reference design, TIDA-00874, can help you with the PCM5242 audio DAC paired with the TPA3251D2 Class D audio amplifier, capable of streaming multiple digital inputs up to 192kHz. Audio format for enhanced sound experience.
Figure 4: TIDA-00874 equipped with TPA3251D2 and PCM5242
Less than a decade ago, we also believed that laser discs delivered the highest quality sound. Today, "Golden Ears" audio enthusiasts will laugh at the sound quality of only 16 bits. Over the past decade, a large number of amplifiers have been available to accompany this rapid improvement in sound quality. Just like we are now laughing at CDs, audio enthusiasts have also ridiculed D-class amplifiers. But now the situation is different. A great example is the DPA3251D2, a Class D audio amplifier that delivers high-definition sound quality. This is the device I mentioned above, it was also shown at CES 2016, and the audience was shocked by its sound effects.
Is there a device that helps you improve the sound quality in your system? This article uses the TPA3251D2 as an example. The same series also includes the TPA3250D2 and TPA3255. So have you had experience with these devices or other Class D amplifiers?
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