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Power of Audio Amplifier?

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cupoftea

Hi,
If someone tells you that an Audio amplifier has a load of 30 Amps at 120Vrms, then what would be the power drawn from the supplying power supply? The power supply provides a DC rail of 175VDC to the Amplifier. Its for a Bass amplifier.

Also, at one point, he described to me that a different amplifier was a constant load to the PSU......that must mean that that one was a class A or B amplifier?
A class D amp could surely never be a constant load? (playing music, or guitar)

If someone tells you that an Audio amplifier has a load of 30 Amps at 120Vrms, then what would be the power drawn from the supplying power supply?
Yes.
But where would you find a 30A, 120Vac outlet?
he described to me that a different amplifier was a constant load to the PSU......that must mean that that one was a class A or B amplifier?
The would be Class A.
Class B draws much less power with no output signal.

Hi,

30A x 120V = 3600W = load power

30A x 175V = close to DC power (assuming class AB or B)
Indeed one has to define what the 30A are. 30A RMS sine. Or 30A peak or random music.
So let´s say RMS sine.
But you don´t use RMS value when you calculate with DC voltage. Use average. in this case rectified average.
RMS sine --> rectified average is a factor of 1.11.
So divide 30A by 1.11 and get 27A.

..and I doubt it draws the same current even without sound.

Klaus

But where would you find a 30A, 120Vac outlet?
Thanks, but sorry, i should have said, i think the 120VRMS was referring to the voltage across the coil of the speaker....these audio people seem to have their own way of referring to power.

Basic way to get at Power in is to divide Power out by fractional efficiency.

Regards, Dana.

I was told that the offline PSU that supplied this "30Amp, 120Vrms" amplifier had a switching frequency of 64kHz, used IGBT's in the primary side, and that there was absolutely no primary side current limiting. I only saw the PCB for a matter of seconds. I was told that there were two opto drivers, so presumbaly two hi side IGBTs....i didnt think opto drivers could do 64khz, at least, not many of them.

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