Luxman C 300 (1980)

Name: Luxman C 300
Brand: Luxman

Nine kilograms of dual-mono Class A control amplifier, built in Japan at the tail end of the golden age - and one of the last Luxman designs to escape the Alpine takeover.

Overview

Luxman's C-300 is a stereo control center, a line-plus-phono preamplifier, released in December 1980 and sold for barely a year and a half on most markets. It is a fully dual-mono Class A design. It weighs 9 kg and measures 47.8 x 16.3 x 38.4 cm. It sits in the company's "Duo-Beta Exquisite Separates" line, a series some markets announced as the "New Laboratory Series." It was built to pair with the M-300 Class A power amplifier, and collectors consistently describe the two together as one of the last classic Luxman combinations to escape the Alpine takeover intact.

The C-300 sat a step below the C-5000A, at almost exactly half its price. It still landed in Stereo Sound's "Best Product" section in the winter of 1981.

It was the cheaper sibling, but it wasn't built like one. The circuit topology, the power supply, the chassis materials and the switching all read as flagship-class work.

Inside, the C-300 uses Luxman's Duo-Beta plusX circuit, a negative-feedback scheme designed to preserve sound quality by minimizing the amount of excess feedback in the signal path. The phono equalizer and flat amplifier stages use cascode bootstrap inputs with high-Gm low-noise dual FETs and current mirror loads. The MC head amplifier takes a direct-coupled FET parallel input into a Class A pure complementary push-pull output. All circuits are DC-servo operated. The flat amp is the same circuit as the EQ section, which keeps the signal path consistent across sources.

The headline numbers are strong for 1980. Total harmonic distortion is 0.005% or less across phono MM/MC, tuner, AUX, and both monitor loops, measured 20 Hz to 20 kHz. Intermodulation distortion is 0.002% or less on the same inputs. Line-level frequency response runs from 0.5 Hz to 140 kHz within ±0.5 dB, which looks more like test equipment than consumer hi-fi. The phono stage holds 20 Hz to 20 kHz within ±0.2 dB. Signal-to-noise on the line inputs is 100 dB, the MM phono stage manages 80 dB, and the MC stage is rated at -148 dB/V input-equivalent noise (IHF-A weighted, input shorted). The MC input is sensitive enough for a 0.09 mV cartridge, with switchable high (100 Ω) and low (50 Ω) impedance loading. The MM input is 2.0 mV at 50k Ω. Line-level inputs - tuner, AUX, and both monitor loops - are 140 mV into 55k Ω. Pre-out impedance is 47 Ω, with a rated 1 V output and a maximum of 20 V. The record output is 140 mV rated into 100 Ω, also with a 20 V maximum.

Key Features

Duo-Beta PlusX Circuit with DC-Servo Operation

The Duo-Beta plusX topology is the reason the distortion figures land where they do. By minimizing excess negative feedback, the design aims to preserve the signal rather than correct it. The cascode bootstrap input stages, with high-Gm low-noise dual FETs and current mirror loads, are the kind of parts selection that shows up in measurement gear. Every circuit in the preamp is DC-servo operated, which means no coupling capacitors in the signal path and no DC drift to chase.

Fully Dual-Mono Power Supply

The C-300's power supply is entirely dual-mono, with independent transformer windings, rectifiers, and constant voltage circuits for the left and right channels. This isn't a shared transformer with two secondaries. It's two complete supplies in one chassis. The payoff is channel separation and a lack of inter-channel modulation that a shared supply can't match. The low-impedance design of the supply is part of why the unit weighs 9 kg.

Dedicated MC Head Amplifier with Switchable Loading

The moving-coil stage is a direct-coupled FET parallel input feeding a Class A pure complementary push-pull output with an added constant voltage circuit. Input sensitivity is 0.09 mV, and the user can switch between high (100 Ω) and low (50 Ω) impedance loading to match the cartridge. There's also a direct MC input path that bypasses the input selector entirely. That suits owners running a single high-end MC cartridge who don't want the signal routed through selector switching.

Twin-T Subsonic Filter and Frequency-Shift Tone Controls

The C-300 carries a passive twin-T subsonic filter inherited from Luxman's first Laboratory Standard Series from 1976. It rolls off turntable rumble without intruding on program material. The tone controls are turnover frequency shift type, so the hinge points for both bass and treble can be moved rather than fixed. A tone bypass switch takes them out of the path entirely.

Line Phase Sensor

The Line Phase Sensor has an outsized reputation among Luxman collectors. It's a back-panel indicator that shows whether the AC cord is plugged in the right way, in phase. Few manufacturers cared about power-supply behavior at that level. Early production C-300s used a round button for this. Later units used the final square design.

Construction and Internal Wiring

The chassis avoids magnetic materials near the circuitry to prevent distortion, and the input/output terminals are gold-plated. Internal wiring is oxygen-free copper 500-core shielded cable. High-quality film capacitors are used throughout, with small styrofoam capacitors in parallel in the power supply for improved performance. The volume control is a continuously variable precision detent type housed in an aluminum die-cast case. The natural wood cabinet, when fitted, has aluminum foil backing for additional shielding. Most switches - monitor, dubbing, and the direct MC input - sit near the back plate rather than on the front panel, which keeps signal paths short.

Historical Context

The C-300 was released in December 1980 and sold for barely a year and a half on most markets. Production years are recorded as 1980-1983 by some sources and December 1980 to 1982 by others. It was one of the last Luxman models produced before the Alpine takeover. The C-300 and its M-300 partner are widely described as the last classic Luxman combo to see at least part of its production run escape the corporate transition. One source gives a price of 220,000 ¥ in 1981, while another lists a retail price of $1,000.00, roughly half the cost of the C-5000A above it. Despite the lower price, it landed in Stereo Sound's "Best Product" section in the winter of 1981.

Some collectors regard the C-300 as a predecessor of the C-05, though no specification relationship between the two models is documented. It was designed specifically to pair with the M-300 Class A power amplifier.

Collectibility & Value

The C-300 is a sought-after collector's item among vintage Japanese audio enthusiasts, and the market reflects that. Units are routinely restored with full recapping and servicing before resale. Listings commonly advertise "fully recapped and serviced" or "complete service, including a thorough check-over, tune-up, and professional cleaning." One listing on Carousell.sg was priced at S$1,580. A Russian listing for a C-300 Control Duo-Beta Plus X appeared at 263,790₽, though exact item attribution on that figure is ambiguous. No confirmed current market price in USD or EUR from a dated listing was found.

Buyers should expect to pay for restoration, not just acquisition. The C-300 is a 45-year-old dual-mono Class A preamplifier with a complex power supply. The standard advice from the collector community is to budget for a full recap and service, or to buy a unit that has already had the work done. No specific common failure modes are documented beyond the general recapping note.