There were many, robustly-built Japanese audio electronics on the audio market in the 1970s. Where they were notably weak was on loudspeakers, but there were many bad loudspeakers of all origins, then, so that was a matter of degrees of terribleness, not binary. In electronics, the Superscope-era Marantz amplifiers, receivers, integrated amps and preamps were both excellent for the time and can still hold up today. Common items like the 22XX series receivers; the 1200, 1120, 1090, 1060/70, 1030/40 integrateds; the 3300 and especially 3600 preamp; and the 500, 250, 240, 150 power amps. I owned several of these models during that decade. Kenwood, Pioneer, Sansui, Technics, Sony, Yamaha, Akai, Harman-Kardon all had a similar tier. The Marantz models generally sounded more musically convincing that Pioneer equivalents at the time. Kenwood was in league with Marantz. After 1976, Yamaha emerged with a somewhat more nuanced sound. Technics models in amplification were the most variable. Sansui was quite far behind but often had the most features (i.e. buttons). In the Zu Audio world, it's fairly common for younger buyers to pair a vintage Marantz receiver or integrated amp with Zu Omens, or Omen Def. I see this happen in the Klipsch market, too. And they acquit themselves quite well.
Luxman then was a cut above, and did cost a little more. Tandberg (Norway) leveraged their reputation in tape recorders to challenge Luxman in this upper mass market specialty tier in the '70s. Luxman of the '70s was uniformly musical in electronics, and their high end amps, led by the m3045b, a Tim de Paravicini push-pull triode (using a proprietary power triode) were in the same sonic class as Audio Research.
But what really sticks in collective memory more were the fabulous Japanese electro-mechanical machines of 1970s audio -- turntables, reel-to-reel tape decks, cassette decks. It was in these machines that the engineering, machining, design, manufacturing and execution prowess of Japan's consumer electronics industry was vividly obvious. Forget about what you think about competing turntable drive philosophies -- a 1970s upper end Technics, Luxman, Kenwood, Luxman, Sony or Pioneer turntable made a Linn Sondek or Thorens turntable look like an insincere joke. A US-made AR was a pathetic example of manufactured product, even compared to same-price entry-level Japanese turntables.
I have two Luxman PD-444 direct drive, dual tonearm turntables that have been in use continuously since they were bought in 1977 and 1979 respectively. I've had Linn, Pink Triangle, VPI, Technics, Rega and others alongside at various times over the past 40+ years. So far, the Luxmans stay. The tonearm I use most is a Stax UA-70, circa 1970 origins. I also have Japan Victor UA-7045 & UA-7082 tonearms from the era on one of the Luxman 444s. Luxman anticipated several things with the PD441/444 that newer turntable builders rediscovered. The plinth is a sandwich of iron plate, chipboard and aluminum, bolted together under tension. The motor was bespoke for Luxman by Tokyo Electric. I made one change, ten years ago, that markedly improved the turntable: The 1970s thinking that a mass-loaded (these things weigh over 60 lbs.) turntable should be supported by damped spring leveling feet has been superseded. With some extensive experimentation I arrived at replacing the stock feet with 1 lb. brass cones, attached to the turntable by thin polymer adhesive discs, and the cones are seated on receptors that are mounted on bearings. This brought the Luxman into the present with jump factor, greater resolution and a new level of bass performance without losing any of the turntable's intrinsic musicality.
The Pioneer, Sony, Teac, Dokorder, Akai, and later Technics reel-to-reel machines were similarly magnificent, and the rebirth of R2R is most often enabled by reborn Japanese decks from this era. In cassettes, a long parade of machines poured out of Pioneer, Marantz, Kenwood, Technics, Dokorder,, Teac, Denon, Akai, Sansui, Harman-Kardon, others.
Unfortunately, as the true mass market that was hifi when Boomers were in college, began to dissipate with the rise of many competing interests for cash, from video to accessible skiing, during the 1980s. And as hifi moved from hifi stores to bigger box retailers, they demanded from the industry packaged systems that less -knowledgeable sales people could sell. So we got flooded with cheap "rack systems" with the plastic content rising and the metal content falling. Luxman got bought by Alpine, the car audio folks. Marantz changed hands, Sony focused on video, TVs, portable audio. Kenwood, Technics, Sansui faded. The receiver pretty much died. CD eventually ploughed under the high-R&D turntables and tape decks. The boom-box became a big, garish thing. And high end audio went ever-higher during the greed-is-good audio-is-status years. The mass market retreated into headphones fed by a Walkman.
In the 1970s hifi had a mass constituency and it made objects of desire average people could afford, and wanted to. See those scenes in movies set in the 1970s, with audio system components on bookshelves shelves? Lots of apartments, dorms and houses looked exactly like that then.
Phil