Luxman SQ-38F (1968)

Name: Luxman SQ38F
Brand: Luxman

The Luxman SQ-38F is a tube integrated amplifier released in August 1968 at ¥78,000. The "F" stands for Final - it was meant to close out the SQ-38 line, though the series went on to spawn further updates (SQ-38FD, SQ-38u) for decades. Luxman built it without a single transistor, at a time when solid-state was spreading rapidly through the Japanese market.

The big change from its predecessor was the output tube. The SQ-38F used the NEC-developed 50CA10, which could deliver 30W+30W in push-pull. That beat the output limit of the earlier triode 6RA8 in the SQ-38D. It was also the first finished Luxman amplifier to use the OY15 output transformer - the SQ-38 had used the slightly smaller OY14. The power amplifier section stayed the same Mullard-type circuit as the SQ-38, while the preamplifier section was further refined.

The preamp section had the LUX System NF variable turnover tone controls - bass at 300 Hz or 150 Hz, treble at 3 kHz or 6 kHz, each with defeat. It also had low-cut filters at 50/100 Hz and high-cut at 5/9 kHz. There was a tape monitor switch and a DIN tape connector. Phono equalization was RIAA, and a tape head input used NARTB. A stereo headphone jack was standard.

The tube complement runs to twelve: four 50C-A10 output tubes, three 12AX7, three 12AU7, and two 6267. Eight diodes handle rectification (four DS-16A, four DS-16C). Rated output is 30W per channel into what the fact sheet lists as a 1MΩ input impedance. That is an unusual figure, and it likely reflects the high-impedance input stage rather than speaker load. Distortion is spec'd at 1% or less at 30W, frequency response 10 Hz - 50 kHz at −1dB, residual noise 0.5 mV or less, and damping factor 16 at 1 kHz. Power consumption runs 180 VA at no signal and 270 VA maximum. The chassis measures 476 × 190 × 335 mm and weighs a substantial 18 kg.

The SQ-38F kept the classic Luxman look, often with a gold front panel. The design traces back through the SQ-38 series, which had become an instant classic in the 1960s. Hi-Fi Hall of Fame notes the model was introduced in 1968 with the 50CA10 output tubes, which matches the Japanese source data.

Documentation on this model is otherwise thin. No period reviews, no service manual availability, and no detailed circuit analysis have surfaced in the research.