I think Kyle's point is very interesting, possibly true, but I can also say that even back in 1974 the Metro Toronto AC line was not what the specs would lead you to expect. Voltage varied with time of day, there were spikes and dips, and there was a lot of hash on the 60 Hz wave.
Today it may well be far worse, and certainly good AC treatment makes a huge difference today to both tubes and ss.
Today it may well be far worse, and certainly good AC treatment makes a huge difference today to both tubes and ss.