DIRECT DIGITAL FEEDBACK AMPLIFIER

摘要

Designed by Zetex Semiconductors and implemented in the M2 by NAD, the DDFA or 'Direct Digital Feedback Amplifier' is a true Digital Class D design, closer in execution to TACT's Millenium amplifier than D-Premier's Analogue/ Digital Hybrid, tested last month. Like all Class D amplifiers, the M2 represents the audio signal as a stream of very high frequency pulses whose 'width' or duration determines its amplitude. Known as PWM or Pulse Width Modulation, this stream drives a high-speed MOSFET switching stage, an LC low-pass filter network being used right at the output to 'reveal' the desired audio waveform.