Generally, most older equipment was one form or other of class A or class A/B amp, with adequate to huge power supplies. the circutry was by force, discrete since there were not that many "works on a chip" SMTs. Turns out, that discrete components are the most accurate way to reproduce sound with less crosstalk and other problems. But it is more pricey, and requires a good deal of hand work, at at least some level. They used a lot of energy up, but made very accurate sound, regardless of their wattage. Speakers were made to be the size they needed to be without such a focus on trading off to make their envelopes smaller than full sound physics allows. Chip amps, especially class D chip amps, are just not that good and have notch, slew, and high frequency problems. but they are dirt cheap, and quick to automate the production of - crank out. The former such equipment designs are still available, but is now even pricer for not being made in high enough quantities, and the price of assembly and skilled labor, as opposed to its less expensive brethren, having taken over the marketplace and manufacturers accountants heartstrings. Also replacing or rather displacing a lot of jobs. the problem with machine assembly being that machines dont buy anything, but I digress. The newer designs allow better power conservation, lighter units, and the ability to pack a large number of channel amps into a reciever sized box. (think 11.2 surround sound amps.) They are lighter, therefore cheaper to ship. Of course well, sound, who cares about sound? Profit IS the product. Good enough to trade with the locals for cash is good enough, right?