On 2019-03-28 10:09 p.m., johnk wrote:
An aside: now that we are talking audio, I would love to get an argument going about Watts RMS ! I say this: the watts specified for an amplifier output are intended to be average power and not rms power.
Any takers?
I do recall that the merchants is North America got into a bit of a "Horsepower Race" with Power ratings on consumer audio equipment.
rather than accept a low number the marketing engineers, started doing things like testing with Pulse inputs to use the electrical capacity of the Filter caps. even further some only tested One channel, (so the power supply was idling on the other.) or connecting a big lab supply as Music is different than sine waves. You started seeing Peak Music Power ratings.
the FTC in the States started cracking down and said that any power claims had to be based on teh RMS output (.707 of the peak) using a sine wave with Specified distortion. AND that the unit had to be conditioned at almost maximum power (75% if I recall, or Perhaps 90%)for several minutes before taking the measurement. SOME units sudenly could not show ANY power as the pre-conditioning was enough to cause them to shut down or Melt down.
I recall seeing a sears catalogue (here in Canada) which showed a 100W stereo, with a small text box titled Truth in Audio stating the the unit was good for 2W under the US FTC method.
So we can blame the US for inventing "RMS Power" - although they were really trying to do the right thing.
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