Sony STR-DA1000ES Technical Background page 14

Two-Stage Pulse Power Supply
The power supply is always a critical component of amplifier sound
quality. And this continues to be true of digital amplifiers. That's why Sony
designed the S-Master Pro amplifiers with incredibly stable power supplies. The
STR-DA2000ES, DA3000ES and DA5000ES take advantage of Sony's two-
stage pulse power supply. At 200 watts per channel across seven channels
(20—20,000 Hz, 8 ohms, 0.15% THD), the STR-DA9000ES required something
even more robust, an absolutely massive Toroidal power supply, discussed later
in this paper.
Simply stated, a receiver's power supply should output stable voltage no
matter what the music is doing. Even during the most demanding musical peaks,
the power supply output should be smooth and steady. Sony's Two-Stage Pulse
Power Supply does a remarkable job in achieving exactly this result. The first
stage is a switching or "pulse" power supply of high performance. The second
stage is an analog constant voltage power supply, for an even higher degree of
stability. The cumulative effect is remarkably stable performance, even when a
rock band is playing all-out, or when a movie sound track includes car crashes
and explosions.
On the left, these fluctuations, at the input of the Pulse Power Supply,
are unacceptable for high fidelity audio reproduction. In the center, the
output of the Pulse Power Supply is substantially better, but still not up
to the standards of Sony ES. At right, after the analog constant voltage
power supply, the power is ready for true high-resolution audio
reproduction.
The pulse power supply of the STR-DA5000ES is remarkably compact
and efficient.
ES Receivers V3.0 Page 14