Ramtubes, AHB2 has load/line regulated SMPS, but as you mentioned, there are losses everywhere. Exact doubling of power for half of the load means perfect regulation - an ideal voltage source, that is only possible with very deep negative feedback. Such feedback might create instabilities or TIM distortions, but feedback in AHB2 is quite different - it is non recursive, meaning that signal is not fed back to the input of the same amplifier but to another "error amplifier" that corrects output later. Such arrangement eliminates instabilities (allowing for wide bandwidth of the amp) and TIM distortions. I also noticed a lot of low bass added , in comparison to my previous class D amp (that had 5Hz low bandwidth limit). My guess is that all DC servos have instability problems for very low frequencies, but AHB2, having no recursive feedback at all can go down to 0.4Hz. Should 0.4Hz vs 5Hz difference be audible with 30Hz speakers? - I don't know, but it is in my setup (big surprise). The same goes for the upper limit - more extension and airy treble. Could this be phase delay at high frequencies with my class D amp? Speaker itself has inductive character at higher frequencies accelerating phase. In addition there are many amps, including one of Lamm, that have lower (50kHz) bandwidth and are praised for wonderful airy highs.