Walkman or Boombox? High end cassette recorder? That is Both those things in TC-D5.
It is a total of four model:
TC-D5 1978 (RCA input)
TC-D5M 1980-2005 (RCA input)
TC-D5 Pro 1982 Professional (XLR Mic input)
TC-D5 Pro II 1986-1999 ($750 1992) Pro 1982 Professional (XLR Mic input)
The TC-D5 was the machine that while clearly not being a “personal stereo cassette player” in the accepted sense of the term contributed immensely to the development of the Walkman idea and the Walkman range. Launched in 1978, it immediately became a favourite of senior people in the Sony company as a source of high quality portable music, despite the lack of suitable lightweight headphones, its large size and its high price. This provided the idea for a cheaper, smaller version that could be sold cheaply enough to become widely popular.
The TC-D5 was not the first Sony portable stereo cassette recorder, there had been many models aimed at both the amateur and the professional user, though they had all been fairly large and heavy, similar in both size and scale to the domestic cassette decks of the period. They were typically based around the mechanicals of the larger machines and had included mains power units and full-sized loudspeakers, all factors not conducive to small size and low weight.
Sony TC-D5 on hifiengine.com
TC-D5 on alkmancentral.com
Sony TC-D5 Service Manual_en （Outline and Assembly for Repair)
Sony TC-D5M Service Manual_en （Outline and Assembly for Repair)
Sony TC-D5 PRO II Service Manual_A en （Outline and Assembly for Repair)
Sony TC-D5 PRO II Service Manual_B en （Outline and Assembly for Repair)