Sony STR-DA1000ES - Manual (Page 16)

ES Receivers V3.0 Page 16
crossover distortion, even when the music or movie sound track is particularly
soft.
Reduced thermal modulation distortion
Analog power amp output transistors create the shape of the audio
waveform directly. Unwanted variations in this waveform are heard directly as
distortion. Unfortunately, changes in the output signal cause momentary heating
or cooling in the transistors. These temperature changes actually alter the
performance of the transistor, which distorts the sound. This is thermal
modulation distortion.
Analog power amplifier. On the left, the waveform can cause
complex—and thoroughly unwanted—changes in the temperature and
performance of the output transistors. The impact on sound is called
thermal modulation distortion. On the right, the transistors perversely
generate the most heat at moderate output levels—the levels you're
most likely to experience most of the time. At full output, heat
generation is near zero.
In dramatic contrast, the S-Master Pro amplifier does not generate
substantial heat. So thermal effects are minimized at the source. What's more,
any small thermal effects that might persist wash out of the signal because digital
amplifier output transistors do not "shape" the output waveform in the way that
analog output transistors must. With the S-Master Pro amplifier, thermal
modulation distortion is no longer a concern.
S-Master Pro power amplifier. Here heating is low and the
temperatures stay consistent over time. On the right, you can see why
digital amplifiers can use much smaller heat sinks.