Why would anyone want class AB amp when class A always sounds better ?


Cost ? Heat? Reliability?
inna
Class A amps (almost) always measure better, not sound better.
Always "unless" the power supply/s can't handle the extra juice need for the higher class-A biasing, then they do sound worse.


Cheers George
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Class A runs very hot and very inefficient , big watts in pure class A is big bucks .
that's why excellent amps ,integrated like Coda give you that option how much bias into class A ,my CSib integrated is close to 20 watts into pure class A , before going to class AB seamlessly to 150-300 wpc If you speakers are fairly efficient 
the amp rarely would ever leave pure class A .
The build quality and engineering skill has everything to do with the end results.
pass labs, class A monos , Coda 16  amp just as a sample just in the U.S  alone.
In Europe Denmark makes several superb class A Amps , as well as classA-AB amps . For power hungry maggis you may need a Big power amp in Class AB 
there are even. Excellent ClassD amps and hybrids that sound good 
and many lower powervacuum  tube amps are in class A up to around 20 wpc and sound very good ,each amp has its own sonic signature.
your speakers have Everything to do with the requirements of your amplifier
and what sound you prefer.