From the Hi-fi critic blog on the DR amps
"Design chief Steve Sells took us through the technology issues. He explained some of the subtleties of power regulator design, noise, impedance and rise time and had cooked up a cunning and revealing demonstration of the improvements achieved in this area. With a well crafted test rig using music feeding power to a silent dummy load, he took three amplifiers through their paces: one unregulated, one standard regulated and one DR regulated, while feeding the now amplified noise and distortion on the supply rail to a loudspeaker.
For the unregulated supply rail the noise was substantial, frankly a noisy racket comprising hum and programme, all half wave rectified, with almost zero music content. In the case of the majority of unregulated amplifiers, some of this noise is also present in the signal to the loudspeaker.
For the regulated power rail the hum and the music distortion was much reduced, this familiar from the improved sound of these established regulated supply power amps. Finally, when the DR amplifier power line was put under the aural microscope, it was essentially silent, free from noise, hum and that dreaded music modulation distortion"