Question for you: knowing that the PA5 provides 83W/4R and 48W/8R with a 144W PSU, how much do you estimate the FB100 with a 400W PSU for 4R and 8R loads ?
We'll know once I send the FB100 for ASR test. But it's around 90W to 100W.
TPA325x clips early if it's voltage limited or current limited. Using a regulated high wattage power supply only means that the PSU will not be a bottleneck and prevent the amp from being voltage or current limited. For example, if you'll use an unregulated power supply on TPA325x, and drive it to clipping levels with sine waves, the power supply voltage will sag / drop, so it will clip earlier. If you'll use a regulated low wattage supply, either the power supply will turn off due to overcurrent protection, or the supply's voltage will sag horribly (depends on the implementation, in case of PA5 supply, the PSU clearly still has some headroom, 144W might be a conservative rating like a 30sec to 5min continuous power since it's closed air, and capable of >= 300W for a burst test).
So using a 400W PSU on FB100 only means that the power supply will not be the cause of early clipping. But the output power of FB100 should still be the same. (Compared to using like a 200W rated PSU). You can even get away with a 150W supply if you don't perform sine wave tests or not using the module as a subwoofer since a typical uncompressed music has a high crest factor. The reserve power on the tank capacitors can handle the short term peaks.
For TPA325x amps with PFFB implementation, the 'knee' of the clipping behaves differently, depending on the PFFB implementation, because behaviors near the clipping point are different depending on PFFB stability / design, so some designs will have a higher THD+N near clipping, hence the 'knee' will happen earlier.
The 83W/4R and 48W/8R figures that you've provided are the 'unclipped' power. But if you allow the amps to clip like on CEA-2006/490A, TPA325x amps should have the same output power assuming the power supply that are being used are equal. And that the amp does not shut down. And that the amp is not voltage or current limited, PFFB design clipping behavior, etc, etc...
For TPA325x amp modules with CLIP/FAULT LEDS, once the CLIP LEDS are 'faintly' pulsing, you can know that the amp module output is on the knee of the clipping without using measurement tools.
FB100 clip leds will start to 'faintly pulse' at 20V / 4R which means that the 'knee' of the clipping will be around ~90W to ~100W. Only way to confirm is to have a power vs distortion test. The knee of clipping is the point before the THD+N starts to climb up exponentially. Also not all 4R loads are created equal
, some do have 4.1ohms, and so on haha. So different test performers will get slightly different results. Even using a 3.8 ohm load vs 4.2 ohm load will have an impact on THD+N results. That's why we want to send our amp to ASR to have a standard reference and so all else will be equal. Same APx555, same load resistor, same environment, etc..
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