Amplification: what are the biggest advances of the last 40 years?

HybridDigital Purifi Eigentakt™ amplification and the integration into the NAD M33, no doubt coming to other amps soon, too.  Distortion level of 0.002%.

There’s better circuitry inside the big fat power cords. This allows for a fatter timbre and deeper colors when you see the musicians on stage

Hands down and far and away the biggest advance in amplification in recent years has been the development of the built-in and custom designed amplification found in high-end mastering studio quality active speakers. There’s still plenty of people who seem to find much pleasure endlessly tweaking, swapping around, ruminating about, and spending inordinate amounts of money on old-fashioned external amps, interconnects, and passive speakers. Enjoy away. But overall and dollar for dollar, the latest top-quality active speakers with line-level crossovers and amps designed specifically and precisely for each *driver* in the speaker very often perform startlingly better than old-fashioned separates. The actual technical details of well-designed internal amplification for active speakers is largely irrelevant.

Active speakers are a good example of how Class D enables things not possible before.  My little but over performing  Vanatoo active speakers are biamped with two Class D amps in each. 

class D