Luxman L 55A (1979)
The L-55A is a Luxman integrated amplifier released in November 1979 and built through the early 1980s. Luxman called it a "Duo Beta DC Integrated Amplifier". The name refers to its feedback topology, which combines two negative feedback loops instead of leaning on a single heavy global loop. The idea was to keep the circuit inherently linear and use only a modest amount of feedback, backed by DC servo control. It's a DC-coupled design with a built-in MC head amplifier that adjusts gain automatically according to the connected cartridge's impedance. A buffered tone control circuit sits in the signal path, so you avoid the losses a passive tone network would normally cause.
It shares its core technology and several design elements with the L-58A, its sister unit, and was intended to pair with the Luxman T-50A tuner. The amp is rated at 80 watts per channel into 8Ω across 20 Hz to 20 kHz, with total harmonic distortion of 0.02% or less under the same conditions. Input sensitivity is 1.5 mV for phono MM and MC-1, 0.05 mV (2 Ω) to 0.15 mV (40 Ω) for MC-2, and 220 mV for the tuner and Aux inputs. It measures 466 × 378 × 181 mm. Original Japanese price was ¥119,000.
Documentation on this one is patchy. Official material is scarce, and the owner's manual and service documentation circulate mainly through enthusiast archives and third-party sources. Owners consistently report that the switchable phono stage and the overall sound quality are the reasons to seek one out. Surviving units occasionally show up with power faults, and cosmetic parts like the treble and bass knobs are hard enough to source that owners have gone looking for L-58A knobs as substitutes. A replacement speaker terminal is still sold aftermarket, which says something about how the original plastic clamps have aged.
- Released November 1979; produced into the early 1980s
- 80 W/ch into 8Ω, 20 Hz–20 kHz; THD ≤ 0.02%
- Duo Beta DC circuit; DC-coupled; auto-gain MC head amp; buffered tone control
- Input sensitivity: 1.5 mV (MM/MC-1), 0.05–0.15 mV (MC-2), 220 mV (line)
- Dimensions: 466 × 378 × 181 mm; original price ¥119,000
- Sister unit: L-58A; matched tuner: T-50A
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