Digital amplifier technology: Reshaping the audio market

摘要

A relatively new technology for audio amplification is gaining increasing popularity in the consumer audio market. This technology―digital amplification―is enabling new possibilities for designers of consumer audio products and is literally reshaping this market. A digitally amplified system (see Fig, 1) allows the audio signal to stay in the digital domain for practically the entire signal chain. The conversion to the analog domain occurs either just prior to the speaker in passive second-order LC filters or sometimes in the speaker itself. This signal chain involves the following steps: 1. A processor or DSP receives digital source material (from DVD, CD, or SPDIF), decodes and/or processes it, then outputs it as PCM data. 2. The PWM processor receives this PCM data, over samples it, applies noise shaping, and then converts the data to PWM format. 3. The PWM processor then passes this PWM data to the power stage, which converts the 3.3-V PWM signal input to a higher output (usually from 20 to 40 V), and then applies the signal to a speaker or second-order low-pass filter where it is now in the analog domain.