Smaller sibling to the KA-9100, less powerful but just as carefully built.
The x100 series was export-only : KA-9100, KA-8100, KA-7100 & KA-6100.
There is a japanese KA-8100 but it is a 1978 lower-end amp with only one transformer and more modern plastic-case transistors, visually closer to the KA-907.
Two transformers, 4x 10,000µF caps and relay-protected output for the DC power supply and amp stages, voltage-regulated preamp stage, back-deported input selector and clear separation of large current / small current areas.
The phono stage is made of a 3-stage FET differential amp with current-mirror load (1st stage), Darlington circuit with current-mirror load (2nd stage) and complementary SEPP output.
The inputs are directly connected to their EQ stages of the preamp board.
Feature are galore, if not "audiophile" by todays' standards : 2-way loudness switch, high, low and subsonic fliters, dual-frequency tone controls and ±10dB input gain switch.
I believe the 2-gang logarithic volume pot to be the same as that of the KA-7300.
Being 1977, this is all metal and the D-7 rack handles were available to make you feel you did get a KA-9100 at a reduced price.
Besides the two TECH tabs here, you can read Zeljko's review of the KA-9100 for the basics of this well remembered series of Kenwood integrated audio amplifiers.
You can also see nudies aplenty of a complete restoration at Curt June's.