After the Dolby-equipped CAD-4, CAD-5 and the popular HK1000, up came the HK2000 which refined what was left to refine for mid 1970s high-end cassette recordings - without going to upcoming Nakamichi science-fiction.
The HK2000 came in the lineups when Sidney Harman was just about to sell H/K to Beatrice Foods so it was part of the first Harman/Kardon components to be Made in Japan.
But it wasn't the first for sure : the HK1000 already was made in Japan and the proximity between the 1000 and 2000 is quite obvious.
By whom both decks were made will however probably remain a mystery...
Precision-machined flywheel, precision-ground belt, DC Servo motor, heat-treated and hardened Permalloy rec/play head and phase-linear circuitry.
But the Constant Current Drive was the major thing : instead of a constant voltage circuit which has magnetic flux variying alongwith head impedance, constant current converts incoming voltage into proportional current to keep output... constant.
Beginning to appear in the mid 1970s, calibration pots are present as well, two for each channel acting differently for each of the two tape positions.
The first affects the 1,5Khz...6Khz region, the second the 6,8Khz...20Khz - that's four octaves of possible EQ.
A 20Hz subsonic switch was added (at the back) alongwith a basic pitch control (at the back too - not too practical).
MPX filter is present, just as a peak LED, a ???Hz calibration tone generator, mic/line mixing, mic input level pots, output faders, separate high and low level inputs and the ubiquitous Dolby noise reduction.
The HK2000 also was available in plain black later in its (short) life, with minor scripting differences. The original silver is much more inviting.
Replaced by the strangely pretty but less ambitious and fully Shin Shirasuna / Silver HK1500 in 1977/78.
An october 1976 Gramophone review can be read at Gramophone's.
A fair, accurate and detailed history of Harman/Kardon at Fundinguniverse.com.