Back in the 70s, 80s, and even into the early 90s there was no such thing as Power Plants or power conditioners for high-end audio. Heck, there weren’t even high-end power cables.
Back then we just plugged into the wall and went about our business.
And we had some great sounding systems back then because everything we knew about mattered. We paid attention to cables and amplifiers and speaker placement. And it all mattered.
AC power issues that we now know held back performance were not a thing. So we did the best we knew how to and got great results unaware of how much better they could be.
I remember the first time I heard a power conditioner. A passive one from MIT. Arnie Nudell and I were shocked at the difference it made.
It took us about a week to realize that while the sound was cleaner and quieter it also had been stripped of its life (as all passive conditioners do to some degree) and so we returned to plugging into the wall.
Everything matters in the audio chain.