Suggestions for amplifier ratings

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If someone is looking to manufacture a modest series of audio amplifiers, say 3 to 5 models, tops, which ratings should these models have?

Obviously, it is not feasible to have a whole range of models, ranging from 50W to 5000W in 50W increments, so I'm looking for some input. Which wattages sell best?

Let's say I decide on three models: 100W, 200W and 500W per channel. Are these okay, or will I find out later that no one wants the 100W, whereas 150W would have been a better choice?
 
As you need 10dB increase to be twice as loud, 10W, 100W and 1000W seems to cover the bases. Or in other words, if 10W isn't enough 50W will also not be enough!
You mean 10dB to be ten times as loud.
This makes sense from a technical point of view. I approve the dB approch.
Not sure it is ok from a commercial or emotional behavior.

What about 9dB steps ( x 8) : 10W 80W 640W
 
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Cool. Thanks all. Now what about headroom/ onset of clipping above rated power? E.g. for a 100W amp, should it be clean up to 100W sine wave, then slowly start distorting/ limiting as the amp goes into overdrive? Under worst case overdrive, the amp is essentially putting out a square-ish wave, which, even at the same peak voltage as the clean sine wave would be about twice the rated power. If you allow that the peak voltage at full overdrive is 120% of the peak voltage of the rated power sine wave, then at full overdrive the amp is putting out 3 times the rated power.

Have I got the figures right (approx) or have I totally lost it?
 
Any suggestions for what is considered up market these days? Btw. I said 'modest range', not modest amps. Meaning 'not too many models'.

Also, any thoughts on the rated power capacity vs. the power delivered under gross overdrive? My rough calculations suggest about 1:3 - i.e. an amp rated to deliver 100W before onset of clipping will be delivering almost 300W if overdriven to the max (nearly square wave output).
 
......................any thoughts on the rated power capacity vs. the power delivered under gross overdrive? My rough calculations suggest about 1:3 - i.e. an amp rated to deliver 100W before onset of clipping will be delivering almost 300W if overdriven to the max (nearly square wave output).
A perfect square wave has exactly twice (2 times) the power delivery compared to a perfect sinewave with the same peak voltage.

An overdriven (clipped peaks) amplifier with just a tiny amount of measured distortion (1% due to clipped peaks) sounds terrible.
Try a sinewave and gradually increase the level into a high impedance load (an 8ohms speaker with a 100r to 1k0 resistor in series). Listen to it just as the scope starts to show mild clipping. It is very clear when the signal becomes clipped.
 
A perfect square wave has exactly twice (2 times) the power delivery compared to a perfect sinewave with the same peak voltage.

An overdriven (clipped peaks) amplifier with just a tiny amount of measured distortion (1% due to clipped peaks) sounds terrible.
Try a sinewave and gradually increase the level into a high impedance load (an 8ohms speaker with a 100r to 1k0 resistor in series). Listen to it just as the scope starts to show mild clipping. It is very clear when the signal becomes clipped.
There is hard clipping (typical of solid state amps) and soft clipping (more common in tube amps, but mimicked intentionally in guitar amps). In the latter, the overdrive doesn't sound terrible as the circuit is designed such that the gain starts tapering off after the signal exceeds the rated 'clean' level. If overdriven by a sinewave, the tops of the sinewave would appear squashed (as opposed to having their heads chopped off flat). I like this approach even in 'clean' amps because it is more forgiving to occasional peaks.

I want to keep about 20% voltage headroom for this purpose.
 
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