Luxman L-550X (1983)
A Class A integrated amplifier released in 1983, part of Luxman's high-end L-500X series.
Overview
The Luxman L-550X is a stereo integrated amplifier introduced in November 1983 as an upgrade to the original L-550. It runs in pure Class A with a fixed bias current and uses a single-stage amplification design. The ground circuit is refined to reduce interference, and there is a head amplifier for MC cartridges. It came out during the "Golden Era" of Japanese high-fidelity audio and belongs to the L-500X series, which is based on the earlier L-500 series. The L-560 eventually replaced it.
Specifications
| Continuous effective output | 50W + 50W (8 Ω, both channels driven simultaneously, 20 Hz to 20 kHz) |
| Total harmonic distortion factor | 0.008% or Less (8 Ω, -3dB, 20 Hz to 20 kHz) |
| Cross modulation distortion factor | 0.008% or Less (8 Ω, -3dB, 60 Hz : 7 kHz = 4 : 1) |
| Input sensitivity | Phono MM: 2mV; Phono MC: 90 μV (direct to equalizer); Tuner, DAD, Line: 150 mV; Main in: 150 mV |
| Input impedance | Phono MM: 100 Ω, 50k Ω, 100k Ω; Phono MC: 40 Ω, 100 Ω, 300 Ω; Tuner, DAD, Line: 40k Ω; Main in: 47k Ω |
| Signal-to-noise ratio (IHF-A corrected) | Phono MM: 86 dB or more (5 mV input); Phono MC: 80 dB or more (250 μV input); Tuner, DAD, Line: 105 dB or higher (input short); Main in: 105 dB or more |
| Frequency characteristic | Phono MM: 20 Hz to 20 kHz ± 0.2 dB or less; Phono MC: 20 Hz to 20 kHz ± 0.2 dB or less; Tuner, DAD, Line: 10 Hz to 100 kHz -1dB or less; Main in: 10 Hz to 100 kHz - within 1 dB |
| Tone control | Maximum variation: ±9 dB; Low-frequency curve points: 55 Hz, 77 Hz, 110 Hz, 155 Hz, 220 Hz, 310 Hz, 440 Hz, 620 Hz, 880 Hz; High-frequency bending points: 620 Hz, 880 Hz, 1.2 kHz, 1.7 kHz, 2.5 kHz, 3.5 kHz, 5 kHz, 7 kHz, 10 kHz |
| Pre-part output | Pre out: 150 mV |
| Power supply voltage | 100 VAC, 50Hz/60Hz |
| Power consumption | 310W |
| External dimensions | Width 453 x Height 174 x Depth 470 mm |
| Weight | 20.0 kg |
Design
The L-550X runs Class A with a fixed bias current. The single-stage amplifier design is there to improve the bare amplifier characteristics. The equalizer and power sections both use a symmetric differential push-pull topology. The ground circuit is refined to minimize interference from ground potential fluctuations. The head amplifier supports MC cartridges, with a low-noise transistor at the input and a high-speed, linear transistor at the output. The power supply uses a pure focus capacitor for blocking, and copper plating on critical areas of the chassis reduces electro-magnetostriction. The unit also has a linear equalizer and a DAD input label.
Context
The L-550X was developed as an upgrade to the L-550, with a larger Bando toroidal transformer and an improved power supply. It belongs to the L-500X series, which evolved from the L-500 series and later included the L-550Z, L-570, and L-580. It launched shortly after Luxman was acquired by Alpine, and the L-560 replaced it. Build quality was high, but it did not sell well, possibly because of its ¥50,000 premium over the standard L-550 and market saturation.
Market
The L-550X has turned up in recent listings at prices such as $1,563 and 60,000 Philippine pesos. Known issues include the twist-lock speaker connectors and the input selector slider, and some units need the volume control cleaned. A service manual is available for purchase, and repair records are documented online.
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