A 2x 90W powerhouse amplifier in 1973 style : wood enclosure holding a massive "hermetically sealed IC core" LUX transformer , two bigga "10,000µF computor grade" caps, equally massive dual heatsinks, "high-speed" power transistors, and DC output stages.
With a few added niceties : dual-rail and stabilized power-supply, high 250kOhm input, fast 2ms VU meters, fixed or variable inputs, two protection relays and plug-in circuit boards (some).
However, as specifications show, slew rate or power bandwidth were still in late 1960s range...
The M-150 was introduced more than a year before LUX's 50th anniversary in 1975.
In true Luxman tradition, a version of the M-150 was made after 1975, named M-1500.
The M-1500 is an exact equivalent but its name fit better the groundbreaking M-2000, M-4000 and M-6000 amps a as a low-price alternative to the M-2000.
It is the same amplifier, though, but Luxman always was... Luxman.
Also inheriting some from the M-150 was the M-1600, this time placed in the L&G lineup : same front, same controls but an entirely different amplifier inside.
Luxman style - again.
Made to be mated with the CL-350 costing 79,000¥ in 1972 (upped to 88,000¥ in 1974) for a nice 221,000¥ high-end combo... and 4000¥ cheaper than the M-2000.
If the M-2000 and M-4000 sold very well despite their price, the M-150 sold rather poorly and the M-1500 is almost invisible.