agedhorse

Thanks Charlie! This is very much the same process that we use when designing amplifiers, developing the combination of load profile, driving signal and thermal conditions, integrating these factors over time. This was even more the case when designing linear amps when we had to worry (a lot) more about SOA (safe operating area). Class D amps are more forgiving in this area than linear amps due to cut-off/saturation operation. While this is correct for voltage, it is NOT correct for power as you would be ignoring the squared factor in the power equation (P=V^^2/R) When RMS is used in describing power, all it means is that the voltage and current are based on RMS units, not that the power itself is in RMS units. It's a short-hand notation that's understood by most professionals in the industry and has been used for years.

I think you are misunderstanding what the rated input power number means and why it's required of any amplifier that is sold in the EU, as it must be tested and certified to EN60065. This regulation specifies that the rated power input be based on a minimum of 1/8 rated audio power (in RMS units) at the lowest rated impedance. It can be higher than 1/8-duty cycle if the amp is specifically designed for this operation, and passes the tests accordingly (many do not, or the companies may choose not to test to extended duty cycle beyond the legally required 1/8-power which is 12.5%) Designers have no choice but to follow these regulations, they are regulations that the European countries have specified that we designers follow. If you don't like it, take it up with the authorities having jurisdiction in your region. The reason for this extends all the way through the audio world, in pro audio for example, this number is used to assist in sizing branch and feeder mains circuits, environmental heating loads and such for installations where many amps may be installed. The same certification standard applies to bass amps. This is a commonly misunderstood bit of information, if you wish to denigrate any manufacturer for using it you might want to understand more about what the number legally means first. Once you understand what this number means on a product that carries an NRTL agency approval, you can then calculate backwards by using efficiency to discover the maximum rated power in RMS terms. I normally don't post here, but am available at TalkBass as many of you here already know.