Luxman SQ63 (1963)
The Luxman SQ63 is a tube-type pre-main amplifier released in February 1963 at ¥37,000. It is compact but heavy, at 390 mm wide and 11.5 kg. It uses ten vacuum tubes: three 12AX7s, two 6AQ8s, four 6GW8s, and a 5AR4 rectifier.
The main feature is a variable crossover MFB (motional feedback) function. Lux developed the system to automatically compensate for the low-frequency response of speakers, which falls off below their resonance point (fo), and it improves response below that frequency. A selector switch bypasses MFB entirely, so the SQ63 can run as a conventional amplifier through its NFB circuit. That is a thoughtful option for a 1963 design, since the special circuitry wasn't always wanted. The catalog of the day recommended sealed (acoustic suspension) speakers with this amp, because their impedance characteristics wouldn't disturb the system.
The front panel carries a balance meter with independent left and right channels, which is an unusual output meter arrangement. Inside, Lux used carefully selected tubes and DC ignition to suppress hum. The case is finished in "Art Bond," a plywood material with a vinyl chloride film bonded to a metal plate. It was chosen for its resistance to fading, scratching, and staining, plus high electrical insulation. The two-tone collar treatment is typical of early-60s Lux styling.
Rated output is 12W per channel into 8 or 16 Ω (switch-selectable), with distortion of 0.6% at 10W/50Hz. Inputs are Tape, MAG (phono), Tuner, and X'tal (ceramic cartridge), with sensitivity of 3mV, 4mV, and 200mV respectively. Tone control is the "LUX New NF Type," with ±16 dB of adjustment. Power consumption is 100W.
Documentation on the SQ63 is thin beyond these specifications. No production end date, no independent period reviews, and no detailed market context have surfaced. The record that exists comes mainly from Japanese audio archives, which corroborate the key figures.
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