Sony STR-DA7100ES Technical Background page 32

One-plate/dual-pellet output transistors
How do you combine the power of parallel output transistors with the
"focus" of single-ended transistors? The STR-DA3100ES output transistors
achieve this with a one-plate/dual-pellet design. Each of these is actually a pair
of matched, high-speed transistors mounted to a common plate. In this way
operating temperatures and current fluctuations remain perfectly balanced. It's
another way that Sony fights thermal modulation distortion. As a further
protection, Sony mounts these transistors on oversized extruded aluminum heat
sinks.
With one-plate/dual-pellet output transistors, the temperature and
current fluctuations of one transistor are automatically corrected by the
complementary transistor mounted on the same plate.
With seven channels of amplification, it's difficult to maintain uniformity.
That's why Sony configured the STR-DA3100ES and DA2100ES power
amplifiers with a master in-line design. This achieves uniformity in both electrical
and mechanical characteristics, for superior richness and imaging.
Lined up in a neat row, the output transistors of the STR-DA2100ES
take advantage of Sony's Master In-Line design.
ES Receivers v1.0
Master In-Line Design
Page 32