They were engineered brilliantly, simply, ruggedly, robustly, militarily, fundamentally, reliably. McIntosh was an absolute champion of magnetics; the art of transformer winding, from the space age, a time where America's best and brightest engineers, extreme scholars of the academic arts of electrical engineering put theory to task and built things as good as they could. It's economically unfeasble to do that today, but back then it was the way of the high end of things. The result was a line of products that satisfied audiophiles and aircraft carriers and the Grateful Dead.
In practice, for players like us that seek tone and sound, the McIntosh transistor series of amps delivers a clean, neutral tone - faithful to the signal that feeds it, but as guitarists that naturally push our electronics to the brink, and beyond, into the realm of clipping and distortion, testing the limits - the McIntosh handles that quite differently than most solid state amplifiers. It handles it without failing, without harshness, but with a toughness and a warmth that somewhat resembles tube amp clipping but stiffer, more solid, and without ugliness. Since the output of these McIntosh amps uses autoformers, technically one half of a transformer yet similar in that it is built on the winding of coils, this seems to be a piece of their formula that contributes to the warmth of the clipping and distortion characterics when we slam them with guitar signal. But much of the tone is in the overall design of the amp circuit and the power supply that powers it.
It's amazing to me that one can buy a Mc2100 or Mc250 or Mc50 for under $3000 today. Actually for under $1000 which is ridiculous. The Mc50 is a miniature gem that weighs under 20 lbs and delivers about 70 watts of power. The combination of a clean, Fender-ish tube preamp signal into a McIntosh into some JBL 12's is just a special thing and something that Jerry learned to wrangle, learned to master actually. It's not a forgiving rig - it demands mastery of guitar picking dynamic control.
There are other ways to emulate and get close to the Tube pre into McIntosh sound, but a real Mac is the sound we know and love, the way the gently distorted Mac is so sweet and squirty and musically fun to hear when pushing a JBL to its limits... it's hard to replicate that guitar sound with anything else. We can get close, but that is a special combo.
... and it's just like any other day that's ever been...