Luxman SQ11 (1963)

The Luxman SQ11 is an all-transistor integrated amplifier released in June 1963 at ¥32,000. It was an early step in Luxman's move from vacuum tubes to solid-state circuitry. The design is an OTL (output-transformer-less) circuit, which was difficult to do with tubes. A special feedback circuit automatically controls excessive current, meant to prevent destruction when large currents flow, such as when the speaker terminals are shorted. A high-dissipation heat sink and generous ventilation openings handle the heat.

The SQ11 is compact by today's standards. It measures 316mm wide, 83mm high (103mm including feet) and 208mm deep, and weighs 5.5kg. Output is rated at 20W+20W into 4Ω, 16W+16W into 8Ω, and 10W+10W into 16Ω at 1kHz. Total harmonic distortion is 0.8% at 16W into 8Ω. Signal-to-noise ratio is rated at 56dB or better across inputs. The tone controls are NF-type, with ±10dB at 100Hz for bass and +8dB to -10dB at 10kHz for treble. Input sensitivity is 5mV/50kΩ for Tape and MAG (phono), 500mV/1MΩ for Tuner, and 250mV/500kΩ for X'tal. The front panel has a rumble filter, scratch filter, loudness control, and phase switching. A universal terminal on the rear lets you use the main amplifier and preamplifier sections independently, or connect a reverb amplifier. The unit uses 20 transistors and 6 diodes.

Documentation on the SQ11 is thin. All specifications trace to a single Japanese source (audio-heritage.jp). Beyond the June 1963 release date, no production run details, lineup positioning, or period reviews have surfaced. One owner noted online that they were given an SQ11 with an internal fault and found very little information about the unit. No dedicated maintenance documentation is known to exist, so servicing means relying on general vintage Luxman knowledge.