On January 20, 2021 at 22:39, buzz said...
There is a misconception that an amplifier "pushes" power to the speakers. The physics is that the amplifier output voltage varies (up to it's maximum) and there is an output current limit.
I will defer to your expertise, but in amplifier theory I believed that the preamp stages up to the drivers were voltage amps, but by the time you get to the outputs, they are current amplifiers. Throughout nearly the entire signal path, the signal comes in on the base and goes out the collector. In the output stage it comes in on the base and goes out the emitter.
Aren’t emitter followers current amps by definition? I know they are unity gain. (Now I gotta go look it up.)
It's really no different from an AC power circuit or a 70V line. A certain voltage is available and each connected device draws some current. For example, on a 120VAC power line, a certain current is available, perhaps 15A. We can keep adding lamps until we reach the 15A limit.
The difference between a lamp circuit and our speaker circuit is that the lamp circuit operates at a constant voltage and our amplifier's output voltage varies with the Volume control setting and the musical content.
In our speaker circuit there are two limits -- the maximum current the amplifier can deliver and the maximum voltage that the speakers can handle. In a lamp circuit we can dim a lamp (operate at a lower voltage than the lamp is rated), but if we supply a higher voltage than the lamp rating, the lamp dies.
I have repaired a ton of speakers, and I am not sure that many have been damaged by voltage, but I think most of them have been damaged by heat, judging by the look of the voice coil. Perhaps it is a byproduct of the voltage of which you mention, but it could just as easily be a byproduct of the current flowing.
Part of the problem is the math that we use for our speaker circuits. If we used the same math approach for AC power circuits, we'd be struggling to figure out how many 144 Ohm lamps we could stack on our 1800 watt power line.
