https://www.manualslib.com/manual/14276/BAndk-Two-Channel-Amplifier-Ex4420.html
I agree that it looks like a good solid amp, but there is a contradiction somewhere between the Input Watts and Output Watts specification.
@PENG any ideas?
Input watts (drawn from the AC line) and output watts (measured at the loudspeaker output terminals) are not the same thing. Although there is a relationship, output watts should always be higher than the power drawn from the AC line in watts. The exact amount depends on the power supply and amplifier's overall efficiency, so there is limited value in comparing the two.
There was a time when the FTC rule applied to every power amplifier, but in the last few decades the requirements have been either watered down or ignored altogether. First was the FTC modifying the pre-conditioning requirement from ⅓ power for 1 hour to 1/6th power for 1 hour. Next was the advent of multichannel amps, which considered themselves exempt as the original FTC rule of 1973 specified mono or stereo amplifiers only.
"Portable" devices have always been exempt, so car stereos and battery-powered blasters never have been compliant. Merely placing a handle on any device also made it "portable" and allowed ignoring the FTC rule.
Also the FTC rule only applies to discreet audio components, so "Home Theatre in a Box" systems or stereo systems that include amplifiers and speakers do not need to comply.
After years of ignoring the FTC rule on multichannel (more than two channels) amps on the basis that the FTC rule did not apply to amps of more than two channels, when the FTC revisited the idea of making them comply with the general requirements of the 1973 rule, the manufacturers successfully argued that those who had bought gear under their previous practice would feel "cheated" if the true nature of the power ability was revealed, and that yesterday's 500 watt multichannel amp would appear to consumers to be much cheaper than tomorrow's 500 watt amp, hampering sales.
So the FTC backed off. Currently there is no real requirement for multichannel amps to comply with the specification rules. All consideration of revising the FTC rule to reflect multichannel amps is currently in a permanent abeyance.
Perhaps worse, there is no current enforcement of the FTC rule for mono or stereo amplifier manufacturers. It's essentially unregulated today.
Some manufacturers (eg Anthem) do rate their multichannel amps as if the FTC rule was applicable, and this practice is worth noting when found.
In a nutshell, the FTC Rule required:
An FTC-compliant power specification must be the most prominent spec listed in all advertising in a font size that is equal or larger than non-compliant specifications.
Amplifier must be specified with all channels driven, and only after a 1 hour pre-conditioning at one third / (now one sixth) power, into a specified impedance that does not result in protection circuit tripping or other aberrations (eg blown fuse), from either 20 to 20,000 Hz at a specified distortion percentage, or at a defined frequency response for high or low-pass filtered amplifiers (such as sub amps).
Also, if the amplifier cannot sustain power into a given impedance after pre-conditioning without aberrations, you cannot specify any power rating into that impedance anywhere on the spec sheet.
Finally, if an amplifier doesn't mention specs in advertising, or is not advertised in a US-based print or video media, the FTC rule can be ignored. So spec sheets that are downloadable PDFs do not necessarily need to be compliant.
