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

I don’t think we can argue ANY technology improved or changed as much as Class D has over this period of time. As some one fortunate to hear early Class D prototypes, to owning ICEpower amps, this technology has really come up.

Some Class D amps beat some class A amps and are beaten by some linear amps, kind of like rock-paper-scissors.  To be in the game the way they are, with huge benefits in size and efficiency to me crowns them as the single biggest innovation in this time period. 

bobbydd

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

For me I found the biggest advances for musicality/listenability came with giving "global feedback" the big flick.✔
And that came with solid state amps that use highly biased Class-a (for sweetness) but with Bi-Polar (BJT) complimentary (npn/pnp) push pull output stages, but being used without musicality killing "global feedback" surrounding them, instead using a small amount of "local feedback" only around the front amplification stage.

But to do this is properly those complimentary bi-polar output transistors that are to be used without "global feedback" have to be hfe matched, and also their emitter resistors, otherwise instability can occur.
Then you have an amp with an "iron fist" especially into low impedances, yet with the real "speaker disappearing", musicality imagining and depth act.

Cheers George

MOSFETs

Biggest advance is definitely the price tag.

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