A Japanese-built integrated amplifier featuring Luxman’s Duo Beta DC circuitry and switchable phono stages for MM and MC cartridges.
Overview
The Luxman L-55A is an integrated amplifier released in November 1979 and produced through the early 1980s. Built by Luxman, it functions as a pre-main amplifier and shares design elements with the L-58A, its sister unit. It was marketed as a "Duo Beta DC Integrated Amplifier," emphasizing its unique feedback topology and direct-coupled circuit design. The unit includes a built-in MC head amplifier with automatic gain adjustment based on cartridge impedance, and a buffered tone control circuit intended to preserve signal integrity.
Specifications
| Power output | 80 watts per channel into 8Ω (stereo, 20 Hz to 20 kHz) |
| Total harmonic distortion | 0.02% or less (8 Ω, 80W, 20 Hz to 20 kHz) |
| Input sensitivity | Phono MM, MC-1: 1.5 mV; Phono MC-2: 0.05 mV (2 Ω) ~ 0.15 mV (40 Ω); Tuner, Aux1, 2: 220 mV |
| Dimensions | 466 x 378 x 181 mm (W x D x H) |
| Power consumption | 300 W max |
| Original price | ¥119,000 |
Design
The L-55A uses Luxman’s Duo Beta circuit, which combines two negative feedback loops to improve amplifier performance without relying on high overall feedback. This approach emphasizes strong inherent circuit linearity, supplemented by a small amount of feedback and DC servo control. The amplifier features a DC-coupled design and includes an MC head amplifier that automatically adjusts gain according to the connected cartridge’s impedance. A buffered tone control circuit is used to avoid signal degradation commonly associated with passive tone networks.
Context
The L-55A was positioned as a high-fidelity integrated amplifier and shares its core technology with the L-58A. It was designed to pair with the Luxman T-50A tuner, suggesting a place within a coordinated family of Luxman components aimed at discerning audiophiles of the era.
Market
Owners have noted the L-55A’s switchable phono stage and overall sound quality as standout features, with some calling it the best amplifier they’ve owned. Units occasionally appear with power issues, and while service manuals are available through third-party sources, official documentation remains scarce. The owner’s manual is accessible for download through enthusiast archives.
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