A few things about McIntosh need noting.

First, McIntosh is "the tube amp" in a lot of people's minds because
of their appearance and because even the most uninformed know that the
Jaspanese have bought most of them up. Also, because of their low
distortion and wide bandwidth and low maintenance (for a tube amp), a
lot of them went to commercial, industrial, and lab applications.

This leads to some unwarranted assumptions. One is that the McIntosh
amps were terribly well built. They were built about to the same
physical standards as a Fender or Ampeg guitar amp of the day. It's all
consumer/entertainment quality parts-vis-a-vis the Marantzes which were
built with Ma Bell grade stuff largely. The chrome top is bent up in a
simple sheet metal brake of prechromed material which was much cheaper
and much less corrosion-proof than the traditional plating process
applied to the fabricated part.

Another is that there is high magic in there, particularly the
transformers. The OPTs are probably cheaper to wind than the best
quality conventional ones of the day. Although the Mac patents have all
run out on their tube amp designs, there was even then Prior Art even
then which would have clearly got one of the key patents thrown out and
many claims of the two others minimized had someone wished to do so.

The current Mac products IMO have serious faults, largely because of
excessive adherence to tube amp practice, ironically. Nonetheless their
(ridiculous) blue meters look neat and that's why they sell.