Slim-line, yes, but full nevertheless.

5-gang (3 for FM, 2 for AM), high Q tuning coil and low-noise FET tuner equivalent to a full 4-gang varicap. The european version has an "anti-birdie" filter added.
Duo-ßeta circuit, monolithic IC for the EQ section for high voltage and low noise, differential amps at input and push-pull config at the output plus careful wiring pattern arrangements for said EQ section, DC output with large high fT and low Cob transistors, flat and tone control amps replaced by a tone control placed in the NFb circuit of the power amplifier to improve open-loop characteristics, variable loudness control and only 0,5mV residual noise.

Only 38W per channel, though, but even if low-budget, classy Luxman nevertheless.