Sony STR-GX80ES Technical Background - Page 5

Why Digital Amplification? After decades of engineering practice, the limitations and awkward characteristics of traditional amplifiers have become so familiar that most engineers don't even notice them: • Complexity. In the context of today's home theater receivers, you have digital source material processed through a digital preamplifier-only to be converted to analog prior to amplification. • Heat generation. Conventional power output transistors throw off much of their power as heat. And heat is always bad for electronics. • Thermal modulation distortion. Changes in the audio signal cause immediate changes in the output transistor temperature, which in turn cause changes in transistor performance! This is thermal modulation distortion. • Crossover distortion. Conventional transistor pairs create crossover distortion, which becomes particularly audible during quiet passages. The normal solution is amplifier bias-which means more heat! • Open-loop distortion. Traditional amplifiers typically generate substantial "open-loop" distortion. The Negative Feedback (NFB) used to correct this can trigger other problems like Transient Intermodulation Distortion. Commonly understood for decades, these limitations are so thoroughly ingrained in home audio design that they're considered "inevitable." Resolving these issues means accepting massive heat sinks, tolerating circuitous signal paths and chasing down transient distortions. Sony engineers sought a better way. Sony's S-Master Pro circuitry overcomes these fundamental constraints by completely replacing analog amplification with digital technology. Digital amplifiers had been around for decades, outside the mainstream of home audio. But great strides in Large Scale Integration (LSI), 1-bit processing and faster MOS FET output transistors have opened the door to a new generation of digital amplifier technology. S-Master Pro: principle of operation In the context of a modern A/V receiver, traditional power amplifiers require the needless complexity of D/A conversion, Low Pass Filtering (LPF) and analog volume control prior to the input. ES Receivers v1.0 Page 5