JasonWells
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OK, let's ask the question why are we trying to determine an amps max power output. two major reasons I can think of, you might think of more. to get an idea how loud it might play, and secondly for comparison to other amps. you may be making a purchasing decision.@JasonWells what is your position on this % figure. Do you have a opinion. What is your back ground on the matter?
We have to assume that the basis of this rating is to be without overtly noticeable distortion. THD is a pretty poor metric of audible quality, but it's what we are using.
So obvious question is where do you define "noticeable". it has ZERO to do with the shape of the curve or its knee. it's a thd level you need to define.
Harmonic distortion is actually quite difficult to hear in music. it's audibility varies with frequency, the ear ERB, masking and so on. So it's pretty difficult, maybe impossible to obtain a definitive figure. however with simple tones you can obtain some reliable numbers. It also turns out you are much more sensitive to hearing distortion with sines because you don't have all the masking effects of broadband music.
The research shows THD figures around 0.1% are the threshold, but this is still dependant on frequency etc etc. Hence my view 0.1% is a sensible fighure, it has justifiable merit. it should bexbelow any audible threshold with music and is conservative in this respect. you can test this really easily yourself, no need to take my word for it.
Choosing numbers at 0.001% level makes no sense to me, it way below audibility and has no justification in the context of the purpose of the test. especially when driving speakers that will have 100 to a 1000x more thd.
my second bugbear is that the levels Amir measures are random. they change on every test. no consistency, no ability to compare. his headline numbers on the graphs of max power are under rated and misleading.
1% is high, too high imo, but still probably not overtly noticeable with a lot of music. so massive complaints about 1% are unjustified imo. at least amps are being compared at the same level. you also have the issue that some amps can't acheive low levels of thd. amir just rated one at 0.85%.
So imo two thd power levels should be presented, one at 0.1% and the second at 1%.
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