Sony STR-DA1000ES - Manual (Page 10)

ES Receivers V3.0 Page 10
The Synchronous Time Accuracy Controller (S-TACT) maintains
accurate pulse timing at the output.
Pulse Height Volume Control
After S-TACT, the C-PLM signal passes to a Pulse Height volume
control—the place at which user volume adjustments are executed. Most digital
volume controls work by Digital Signal Processing. They adjust the sound by
multiplying the samples by a coefficient between zero and one. For example, to
achieve a volume setting 6 dB below maximum, you can multiply each sample by
0.5. This yields accurate results, but it does sacrifice some detail at the least
significant bit. Sony demanded more.
The full power pulse (A) represents the maximum setting of the volume
control. To turn the volume down 6 dB, the receiver cuts the voltage to
the power pulse generator in half (B).
In contrast, the Pulse Height Volume control adjusts the 1-bit C-PLM
stream by adjusting the regulator that supplies voltage to the power pulse
generator. Because this method does not modify or reshape the original digital
samples, there's no loss of information, no loss of detail. Sound quality is
maintained from very low volume settings like -50 dB all the way to maximum.