( PEP, Total out put, Peak, all carefully arranged to reflect the best result in the test amp ).
Ack! PEP is a single-sideband measurement! Yes, I saw one of those measurements that turned a +-12 volt supply into a "72 watt amplifier into 8 ohms". How, well, the "swing voltage" was 24 volts, so E^2/r was 72. Wait, well, except, the real peak power into a load isn't that, it's 12^2/8. That's 18 watts.
Oh, but wait, that's peak. Divide by 2 for sinewave power, that's right, ladies and gentlemen, a 9-watt amplifier (and that's only 9 watts IF the output transistors have zero saturation voltage which they can't, ever) is called a '72 watt amplifier'.
Yes, it was time to "do something".
The FTC finally said enough! and when all had to test thier at the same standard ( both channels drive into an 8 ohm load and measured using the RMS formula for output and %THD )
Of course, let us remember the famous "preconditioning test" that ensured maximum stress, give or take, on the amplifier under test, a situation that is almost NEVER actually in existance. But, be that as it may, at least we got real continuous power ratings out of the process, ones that had some marginal connection to actual performance.
what do you think happened? They started inventing other representations of qualities of the equipment that had almost nothing to do with anything a human could experience.
My two favorites were Pioneers "Slew Rate Distortion" and the more general "toridial VS regular core transformers field collapse" ( it doesn't matter what they mean really , they are really non-applicable to audio gear).
Hold on, there, I had some amps whose full power bandwidth WAS less than 20kHz. So slew-rate limiting DID matter for some period of time, although that was fixed once people knew about it. More annoying was that "TIM" (Transient Intermodulation Distortion) was invented as a term for slew-induced distortion, and trumpeted about as a "brand new thing". (*&(* man, op-amps in analog computers in the 1950's and 1960's had warnings about slew rate limiting, and spec'ed slew rate as a matter of course.
So something 20 years old was a 'new discovery', something that seems to happen over and over in the audio industry.
I missed this transformer thing completely, thankfully. What I didn't miss was the bizzare "music power overhead" specs that started to appear, stating how an amplifier could put out more than the usual amount of power for some small amount of time.
What THAT translates into is "we get a better rating on that, i.e. more dB, if we use cheaper, smaller filter caps that have less power supply regulation". So now we have amps selling themselves as 30 watt/channel amps with "3dB music overhead", that were arguing that they were better than a 60 watt/channel amp with no overhead to speak of. The ONLY difference? The 60 watt amp had a sufficient power supply, the 30 watt one didn't. They both do the same thing in the short-term, only the 60 watt amplifier can do it around the clock, and the 30 watt amp only for some milliseconds.
Riiiiight.... A way to make an insufficient power supply sound good. Cooooool,right? (no, in fact, blazing hot, they undersized the heat sinks too)
My setup in the late 70's : Infinity QLS 1, Phase Linear 4000, Fisher 500c ( moving coil preamp only), Crown power amp, Onkyo servo turntable w/infinity black widow arm and an ortofon moving coil cartridges. Drool now! and lotsa #12 zip cord from the local Ace hardware. Oh Ya and I bought it all from Pacific Stereo from some guy who wore Earth Shoes = )
).
(seriously, they were ok as long as you kept them COOL)
) and actually cost less than those horrible Bose speakers. Of course, Bose has to pay for all that marketing.