2nd there is no standard. In most amps in fact bias is adjustable. What you may not realize is that its simply a trade off of heat vs "class-A-ness". I honestly find very little difference between a truly high biased AB amp and class-A, and i can simply turn the POT.
I designed and manufactured a very high bias amp in the mid 1990s - ran class-A about 40% of its rated power (which, for heat reasons and others, was accordingly modest). The prototype remains my "daily driver" today. Sometimes 2 in monoblock mode, but usually I'm swapping things too often to go to that level of complexity.
Given that music has a peak:average ratio of about 10, an amp that is 50W and is 5W class-A would only be out of class-A operation a small % of the time, and those times would be major crescendos when subtlety is more of less completely masked anyway.
G
I designed and manufactured a very high bias amp in the mid 1990s - ran class-A about 40% of its rated power (which, for heat reasons and others, was accordingly modest). The prototype remains my "daily driver" today. Sometimes 2 in monoblock mode, but usually I'm swapping things too often to go to that level of complexity.
Given that music has a peak:average ratio of about 10, an amp that is 50W and is 5W class-A would only be out of class-A operation a small % of the time, and those times would be major crescendos when subtlety is more of less completely masked anyway.
G