The 1980 Akai's AM-U02, 03, 04, were excellent with dual power supplies, large transformers and caps, but the better integrated amp was the Akai AM-U06, which had the pulse power supply. Using a small transformer on a flip,flop transistor board, putting out high voltage, 300V+, at an extremely high pulse frequency, which is then rectified to a very stable DC. This negated all the disadvantage of hysteresis and EM incumbent with large transformers. The epitome of this type of power supply was used in the PA-W04, PA-W06 power amps, with their matching PR-A04, PR-A06 preamps. Excellent specs and matching excellent sound from these separate amp, preamp units.
After this innovative apex, Akai went down the conventional solid state stereo amp road, same as all the other mainstream audio companies like Marantz, Nad, Denon, Luxman, etc., (competition of course). But their faceplate designs became too plain and "tinny" looking, and the black face was the beginning of the end.