Regarding SE Triode amplifiers in Japan, it may be traced to a guy named Jean Hiraga who discovered the WE 300B while living in France then conveyed its magic in a magazine article in Japan. This was 1973. Later in the decade and into the early 80s, a flurry of single ended triode amplifiers appeared in Japan. Some were based on Westrex 91A (designed by Western Electric) amplifiers using 300B triodes.
Read Eric Barbour's article "History Of The WE300B And Its Relatives" in Vacuum Tube Valley (begins on page 8) about the history of the Western Electric 300B and how it spread to Japanese audiophiles.
http://www.jumpjet.info/Pioneering-Wireless/eMagazines/VTV/VTV03.pdf
Read Eric Barbour's article "History Of The WE300B And Its Relatives" in Vacuum Tube Valley (begins on page 8) about the history of the Western Electric 300B and how it spread to Japanese audiophiles.
http://www.jumpjet.info/Pioneering-Wireless/eMagazines/VTV/VTV03.pdf