Luxman SQ5Bb (1965)
The Luxman SQ5Bb is a tube integrated amplifier that came out in June 1965. It refined the company's best-selling SQ5B (SQ5A), which had been on the market since 1960. The price was ¥37,200. The changes from the earlier model were modest. A tape input terminal was added, and the power supply moved to silicon rectification.
The front panel has a power indicator that is also a meter. It shows left and right output levels separately and can indicate stereo balance. The cabinet uses "Art Bond," a vinyl-and-metal plywood material from US Rubber Co., chosen for resistance to fading and scratches. It has a two-tone finish and soft rounded corners, made with a unique pressing technique. The design earned a Good Design selection from Osaka Design House.
The amplifier uses nine tubes: three 12AX7s, two 6AN8s, and four 6BQ5s in the output stage. It is rated at 14W + 14W at 50 Hz with 1% or less distortion. Frequency response is specified at 20 Hz to 20 kHz within ±1 dB. Luxman developed its own NF-type tone control circuit to get rid of the distortion at the flat position that plagued conventional designs, and a click-stopper marks the detented flat position. Output taps cover 4, 8, 16, and 32 Ω loads. The tone control range is ±16 dB, and equalization is RIAA for magnetic phono and NAB for tape. The transformers are Lux-made throughout and carried a 10-year coverage.
- Output: 14W + 14W (50 Hz, 1% or less distortion)
- Frequency response: 20 Hz – 20 kHz ±1 dB
- Tubes: 12AX7 ×3, 6AN8 ×2, 6BQ5 ×4
- Inputs: Tape (2mV/100kΩ), MAG (3.5mV/100kΩ), Tuner/X'TAL (270mV/2MΩ)
- Output taps: 4, 8, 16, 32 Ω
- Dimensions: 390 × 155 × 290 mm; 11.2 kg
Documentation on the SQ5Bb is thin beyond its Japanese-market specifications. No owner reviews, production end date, or common maintenance issues are recorded. A used unit listed as "junk" on Yahoo Auctions Japan drew a bid of ¥2,600 in late 2024, so units do still turn up. The limited period record describes the SQ5B lineage as a bestseller for Lux, and the SQ5Bb as its carefully considered evolution.
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