Luxman's last really successful integrated ampllifier : even a bestseller in those pre-bubble-bursting days of 1989.
Successful here is meant market-wise : sound-wise, both the L-540 and L-570 were here and there tagged as "reference", "absolute" or "State of the Art", thus topping the already very successful line that started two short years before the Alpine days with the L-550 series in 1981.
The L-540 and L-570 are visually identical but for the second pair of speakers and the phones output which the L-540 adds ; inside they are however almost entirely identical.
The L-540 offers 2x 110W in Class AB, superlative componentry, a non-resonant composite chassis base, dual copper-plated Heat-Pipe cooling system, a big EI transformer, the STAR grounding circuit, ALPS tone & balance pots and a superb rosewood case.
The attenuator is a "special" (ALPS) 4-gang attenuator, the latter becoming a Luxman obsession in later years and after Alpine somewhat went.
It seems some early batches had the "ultimate attenuator" of the L-570 : a big box holding two glass-epoxy PCBs etched with 32 non-magnetic P-shaped gold resistors.
Feature-wise : the Line Phase Sensor, a processor loop, separate inputs for MM and MC, a balanced input and LUX's typical "tilt" tone compensator.
The L-540 is the bold bolid of the two : the L-570 is sweeter, "slower", more laid-back.