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Re: What units are you talking about

Hi Dan, all

Some thoughts about switching, for a PWM or Phase Modulator, neither of these function as a Voltage or current amplifier without a feedback loop.
The PWM or PM is a duty cycle modulator, what happens on the output is largely a function of the load.
Servomotors have been driven by switchers for ages, I built a few for the Servodrive speakers back in the 80’s. Making one go to >20KHz is possible because of a 10 or more times higher switch rate (typically) than was possible with that current level back then.
Also, since the minimum on time thresholds for output switch devices are finite and are somewhat nonlinear as a function of control voltage or shift , this is another reason a loop is always employed somewhere.
As such I am not sure IF one could even have a switching amplifier that didn’t have feedback to linearize it and make it into a Voltage input = Voltage output amplifier.

So far as damping, it may be worth pointing out that so far as its operation, a direct radiator speaker operating well above its Fb, will in fact be current driven so damping factor is not important (or have an impact on the measured result). Keeping in mind it is an R/C filter and the current drive is the voltage across Rdc acting against a C which has a tiny voltage (radiator velocity back emf) across it.
It is control at resonance where damping factor matters and then above say 20 - 50 its irrelevant.
On the other hand, a lowish source Z above is a good idea because the crossover can impose impedance changes that you do not want reflected into the amplitude.
Best,

Tom Danley

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