Luxman SQ38Ds (1965–1968)
The SQ38Ds is the Luxman SQ38D integrated tube amplifier without the built-in step-up transformer for low-output cartridges. It came out in November 1965 at ¥54,500. Otherwise it is essentially the same as the SQ38D: 10W+10W output, 6RA8 output tubes (an MT-type triode equivalent to the 2A3), and the Lux OY-type output transformer with its Orient Core and hand-wound construction. The differences are small. The SQ38Ds dropped the booster transformer, replaced one auxiliary input with a regular tape input/output, and added the DIN tape terminal. Both models could handle modern but low-output moving magnet cartridges, and their backplates carried the same name.
The circuit is serious 1960s engineering. The driver stage uses 12AU7 and 6267 tubes in a leak-type configuration (the same approach used in the UK's LEAK Point One amplifier), and the output tubes run in fixed bias. Negative feedback is 16 dB, which gives a damping factor of 16. The power supply uses a low-flux-density transformer with silicon diode voltage-doubler rectification plus a choke coil. The preamp section runs DC on all stages to eliminate hum. The equalizer and tone control stages are both NF-type, and the Lux-type tone control restores flat response without a defeat switch. Tone adjustment is ±8 dB at 100 Hz and 10 kHz.
The full tube complement is eleven tubes: four 6RA8 outputs, two 12AU7, two 6267, three 12AX7, plus a pair of SE0.5a diodes and two SK-1 rectifiers. Input sensitivity is 4 mV on phono 2, 2 mV on tape, and 100 mV/500 mV on the two aux inputs. Signal-to-noise is 60.5 dB on phono, 58 dB on tape, and 62 dB or better on aux. RIAA equalization is standard on both phono inputs, and tape uses NARTB. Power consumption is 135W at maximum output. Dimensions are 470 × 175 × 275 mm, weight 14 kg.
The 38D and 38Ds sold in enormous quantities in Japan and are still easy to find today, though not cheap, at roughly €2,000. As The Vintage Knob put it, specifications and power output pale beside more modern amplifiers, yet the 38D kept selling on sheer design perfection and whatever musical quality made it the starting point for so many Japanese audiophiles. The original SQ38 from 1963 is much rarer.
A note on the reissue: Luxman produced an SQ-38D Reissue between 1998 and 2000 (only 500 units) that swapped the 6RA8 tubes for 6BQ5, added a fifth input, and altered the phono 1 circuit for MC cartridges. That is a different model from this one. The original SQ38Ds uses 6RA8 tubes throughout.
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