MOF wrote:Here’s hoping Hugh, or someone else well versed in electronics, will explain how this amplifier gets more power out than its input.
Even the RMS figure of a 500watt peak doesn’t work for me.
It's more about physics than electronics imho. Power is energy over time. So 500Watts means that the amp is capable at most to produce 500 joules of energy per second without melting. It doesn't say that for how many seconds it can do that - not even if it can do it for an entire second. Technically it doesn't even say that the speaker won't explode when the amp does briefly produces 500 joules, but of course there's an expectation that all the component in a device can handle the peak power made available by the energy-producing unit..
So 500W means that the amp circuitry is rated not to melt or explode when it occasionally has to pass all that energy, and the speaker and speaker actuation mechanism can sustain that energy for just a little longer time than the amp is capable to produce it.. but that's about all that it means.
Peak power (i.e. maximum instantaneous power) is always a questionable measure to compare devices, if it's not accompanied by data on how a device develops and can sustain it over time. There are always better ways. Not just in amps, but in everything. If you take a car analogy, a Tesla Model S 100D "has" 605HP (451KW) of power. A Bugatti Veryon has 987HP (763KW) of power. Yet the Tesla is quicker (on a straight line) because of the way it develops and sustains that power (till it goes out of juice, that is
). The trick is that "has power" means "has maximum power" and tells you nothing on how it develops. Hence the Tesla wins drag races. If you looked at the integration of power over time (the max energy that can be made available over time) then you get a far better picture. You will see that in the same 10 seconds a Tesla produces much more energy than the Veyron, even if its peak power is lower. That's why it wins races.
Same with a person.. a power lifter athlete can lift say 150Kg, and so can a small forklift. They "have" the same power. But the athlete cannot do it for more than a second, the forklift can do it indefinitely. Real-world performance is not about peak power.
Peak power is useful - you need to know it when you design a device, so that you can ensure that all the parts of the device can withstand it when it happens. And in power lifitng. But not so useful to compare stuff.