Sony STR-DA9000ES - Manual (Page 5)

ES Receivers v1.0 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.