Sony STR-DA1000ES - Manual (Page 18)

ES Receivers V3.0 Page 18
The internal layout of the STR-DA4ES analog amplifier is driven by the
issue of heat dissipation. The entire design is dominated by the output
transistor heat sink fins.
In dramatic contrast, the power amplifier of the STR-DA2000ES is
amazingly compact. The S-Master LSIs (1) convert the signal to a
Pulse Length Modulation 1-bit stream. Thanks to low heat generation,
the power output transistor heat sinks (2) can be quite small. Finally,
the Low-Pass Filters (3) convert the power pulses to audio for the
speaker terminals at the top of the picture.