Remember that these were all variations in how to measure the power output
of an amp back in the '60s. As the time went on, the method of rating the
amps got more and more fancy as the advertising guys found new ways of
measuring the voltage out of the amps and turning that into watts of power.
Some of those ratings were based upon non-real methods of measuring things.
Also note that back then, regulated power supplies were not common with the
amps so there was a difference bnetween what an amp could put out for 1
cycle or continous output. Thus, an amp that could put out 1W could
possibley put out 5W for that one cycle of output! That is a big
improvement in being able to sell the amp in a higher price class!

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Why isn't there an Ozone Hole at the NORTH Pole?