Hi erik, I think the most significant changes are in the quality of semi conductors and other parts not topology when it comes to A and AB amps. The most significant new topology is switching amps, class D and other formats. I think there is a lot of room for improvement in switching amps. I will be first in line if someone can come up with a switching amp that can match an amp made by Nelson Pass or John Curl without torturing my electric bill and air conditioner. Look up the design of the Tact S2150 amp. I think Lyngdorf still uses this design. It is a very high speed pulse width modulation switching amp. It does a fine job driving moderately efficient dynamic loudspeakers. I think this design has more potential than other switching designs. The problem with coming up with a larger version had something to do with the availability of high current devices than could switch fast enough. What this amp really is is a power DAC! It takes a digital signal and turns it into analog in the output stage.
Hopefully Lyngdorf will advance the design. In spite of all this cool technology I have my eye on the Atma-Sphere MA2. It does a fine job driving electrostatic speakers and is reputedly one of Roger West's favorite amps along with the JC 1 and a few others.
