20 Year Old Amplifiers compared to 2017

Thanks for this thread -- it's raising all kinds of points that make me realize how much I have to learn!  willemj started his post with a statement that I don't understand:
"Amplifier technology reached maturity in the seventies, when output transformers were abandoned in solid state amps. Ever since, well designed amplifiers used within their specifications have exceeded human hearing acuity. "

Could someone point me to a source that would help me understand this?  I thought all power amps, even Krells, use power transformers, so he must be saying that less sophisticated amps have two transformers, one of which is on the output stage.  Assuming this is correct, what is the difference in their function, and why is it bad for SS amps to have transformers on the output stage?

Sorry I'm such a newbie, but we all have to start somewhere.

Some may disagree, however I believe MID-FI gear really took a hit in the late 70's until the 90's. Much of it build wise. Pioneer had those gross tan, plastic faceplates. Technics had cheap looking "graphs" printed on the faceplate, AKAI tape deck LED meter strips only had 5 lights per channel, just junk everywhere

Amplifier technology reached maturity in the seventies, when output transformers were abandoned in solid state amps. Ever since, well designed amplifiers used within their specifications have exceeded human hearing acuity.

@cheeg, As I pointed out earlier, the statement you quoted isn't correct on several counts. I did not address the output transformer bit, but other than MacIntosh, that really wasn't a thing with solid state amps even in the 1960s. It may be that what he really meant to say was 'coupling' or 'driver' transformer, as a good number of older designs from the 60s and early 70s did employ audio transformers to drive the bases of the output transistors in the design.

As far as 'their specifications have exceeded human hearing acuity', this statement isn't true either for the reasons I stated earlier in this thread.

@atmasphere,  thanks for your input —   That sounds like a plausible interpretation of what willemj  meant by his opening sentence. I’d be interested to hear Will weigh in here, especially if he meant something different.  As far as the second part of his statement (“exceeded human hearing acuity”), I would agree that is pretty subjective, as  evidenced by the many contrary opinions on this thread. 

interesting how the human ear and the ear/brain connection is so rarely mentioned in debates about the meaning of measurements...