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.