Part of Luxman's last "fairly visible" units during the semi-withdrawal to the japanese market, after the mid 1990s change of ownership. The C-10 and C-9 preamplifiers are "Ultimate" in everything - and mostly where it counts most: the attenuator.

The C-10 and C-9 are almost identical but for a slightly thicker non-resonant 5-point base on the C-10. The real difference is in the attenuator: "Ultimate Volume Control" for the C-9 and "Super Ultimate" for the C-10. The former is a 4-gang high-precision device housed in brass with ±0,5dB balance error between 0dB and -90dB ; the latter is... much bigger: 456 hand-assembled fixed resistors make for a 58-contact attenuator inducing only one resistor per channel in the signal path at any volume setting.

Circuits, i/os and features-wise, both versions are otherwise identical. Sound-wise, the C-10 is ultimate indeed. The production-run is anybody's guess but these are extremely rare...
The C-9 would see a subsequent version (C-8f), still available today in Japan.