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ES Receivers v1.0 Page 14
be isolated from other circuits. On big amps, you'll usually find the output
transistors bonded to heavy aluminum heat sinks somewhere at the back or
sides of the chassis. Thanks to the cool running of Sony's S-Master Pro
amplifier, the MOS FETs are located where the circuit topology is shortest and
simplest—lined up side-by-side, right in the middle of the power amplifier circuit
board. In fact, the transistors can be so close together that the STR-DA7100ES
amplifier section is some 70% smaller than the DA9000ES amp section! And the
board itself is located in the middle of the DA7100ES chassis.
As a result, the music is less exposed to vibration, radiated hum and
noise. Operation is cool and consistent. And nothing intrudes between you and
the sound.
Traditional amplifier STR-DA7100ES
Transistor heat
Major design concern Minor issue
Transistor packing
Widely separated Close together
Transistor location
Away from heat-sensitive parts Surface mount directly on the
amplifier circuit board
Transistor heat radiation
From the bottom From the top
Heat sinks
Massive radiating fins made of
die cast aluminum (on the
better amplifiers)
A single sheet of metal
Space requirements
Major, for high powered
amplifiers
70% smaller than the STR-
DA9000ES—and far, far
smaller than analog amps of
comparable power
Amplifier board location
Isolated, to protect other
circuits from heat
Wherever it makes the most
sense for the shortest possible
signal paths
Overall chassis topology
Circuitous, because of output
transistor heat
Short, simple and straight
Molecular Bonding
Even inside the MOS FET output transistors, Sony innovations are at
work. Sony uses a new refinement of our molecular bonding technique to attach
the transistor leads. In the STR-DA9000ES, the MOS FETs use "double wire
molecular bonding" with two bonding wires, each rated for 15 amps of current.
As a result, the DA9000ES MOS FET binding wires had 30 amp capacity. This
was sufficient for the transistor's rated instantaneous current supply of 24 amps.
The bare transistor for the STR-DA9000ES MOS FET, showing the
double wire molecular bonding.
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