Luxman 5T-50 (1977)
A top-of-the-line Laboratory Reference Series FM tuner that cost ¥220,000 in 1977 and still locks onto stations.
Overview
The Luxman 5T50 weighs eight and a half kilograms and sits in a chassis 442 mm wide and barely 101 mm tall. It doesn't drift. It doesn't overload. It doesn't sound like a tuner. Released in June 1977 at ¥220,000, it topped Luxman's Laboratory Reference Series, a lineup that also included the 5C50, 5M20, 5M21, 5F70, 5T10, 5G12, and 5L15. The 5T50 was the flagship FM front end of that family, and Luxman's own advertising billed it as "a very remarkable component - by itself or as part of a complete LRS system."
The tuning architecture is what set it apart. Luxman built the local oscillator around a frequency synthesizer controlled by a phase-locked loop, with the station frequency set directly by digital code rather than by a variable capacitor. That's a PLL synthesizer in 1977, in a component aimed at the same listeners who were still buying mechanical dial tuners. The front end used MOS-type FETs for both the high-frequency amplifier and the mixer stage, with a buffer circuit after the low-distortion local oscillator to sharpen the interference rejection. The IF strip combined two sets of 4-pole block filters with ceramic filters. That pairing let Luxman go after high selectivity without paying for it in distortion. A double-tuned quadrature detector rounded out the RF chain. High Fidelity (October 1977, p.100) noted that it kept distortion low while protecting against signal overload.
According to the period coverage, the tuner behaved less like a radio and more like a piece of laboratory equipment. The specifications back that up: 1.7 µV (300 Ω, IHF) practical sensitivity, a 1.1 dB capture ratio, and 90 dB image, 100 dB IF, and 65 dB spurious rejection. Those numbers put the 5T50 alongside the best tuners of its year. Mono THD measured 0.1% at 100 Hz, 0.08% at 1 kHz, and 0.15% at 6 kHz. Stereo distortion ran 0.15% at 100 Hz, 0.1% at 1 kHz, and 0.2% at 6 kHz. Stereo separation held at 40 dB at 100 Hz, 45 dB at 1 kHz, and 40 dB at 10 kHz. Signal-to-noise ratio was 70 dB.
Key Features
PLL Frequency Synthesizer Tuning
The 5T50 uses a phase-locked-loop frequency synthesizer to generate the local oscillator signal instead of a mechanical variable capacitor, and the receiving frequency is set directly by digital code. Everything else in the tuner follows from this choice. It removes the drift and mechanical wear that plague analog-tuned receivers, and it allows precise, repeatable station selection, which was genuinely novel for a 1977 consumer component.
MOS-FET Front End with Buffered Local Oscillator
The high-frequency amplifier stage and the mixer stage both use MOS-type FETs. Luxman added a buffer circuit after the low-distortion local oscillator to improve interference rejection. That helps in urban RF environments, where strong local stations can overwhelm a weaker one. Combined with the 100 dB image and spurious rejection figures, it's why the 5T50 can pull a distant station out from under a local blowtorch.
Two Sets of 4-Pole Block Filters Plus Ceramic Filters
Luxman's IF stage isn't a single filter type. It's a hybrid: two sets of 4-pole block filters chosen for phase behavior, plus ceramic filters for raw selectivity. The block filters keep distortion low and the ceramics keep adjacent-channel rejection high. The measured alternate channel selectivity is 70 dB / 62 dB. A double-tuned quadrature detector follows, chosen because it resists overmodulation without adding distortion. HiFI-Stereo (March 1978, p.117) repeated that claim in its own coverage of the tuner.
Seven-Station Electronic Memory
The 5T50 stores seven stations in a C-MOS IC memory element. They're written as digital code and kept even when the power is switched off. There's no battery and no mechanical preset, just electronic memory. Stations can be stored and erased at will. Seven non-volatile presets was a serious convenience in 1977, and it made the 5T50 feel a bit like computing equipment.
Auto and Manual Tuning
Auto tuning scans up or down when the tuning key is pressed, and stops on the next station it finds. Manual tuning moves in 100 kHz increments with a tap of the UP or DOWN key. Press and hold and the frequency sweeps at a preset speed. Release to stop.
Numeric Signal Quality Indicator and LED Dial Scale
Reception quality is displayed as a number from 0 to 5. It's a signal-quality indicator, not a simple signal-strength meter. The dial scale uses 14 LEDs to mark every 1 MHz between 76.1 and 89.9 MHz, plus 10 additional LEDs subdividing each MHz into 100 kHz steps. The frequency is read from the numeric display and the LED scale together, with no mechanical dial pointer.
Recording Calibrator and Multipath Detection
Luxman built in a test-tone oscillator specifically for setting tape deck recording levels, plus an audible multipath detection circuit — a feature that lets the listener hear reflections and antenna misalignment rather than just guessing at them. Muting level, scanning speed, and output level are all adjustable, and an antenna attenuator is provided for strong-signal environments. These are the features that separate a top-of-the-line tuner from a mid-range one: the 5T50 assumes the owner is going to use it seriously.
Laboratory Reference Series Stacking System
The LRS components were designed to stack. Legs sit on the underside and metal brackets on top, joined by metal supports so that a stack of LRS components doesn't press down on the unit at the bottom. The legs and brackets are shaped to interlock, so the stack doesn't slide or tip. An EIA-standard rack mounting bracket was available as a separate optional part.
Collectibility & Value
The 5T50 is a niche collectible. The Laboratory Reference Series as a whole has a following, but the tuner isn't as widely chased as the brand's integrated amplifiers or power amps. Firm pricing data is thin. A Dubizzle UAE listing surfaced at AED 499, and an original Luxman 5T50 tuner service manual has been listed on eBay.ca at C $40.82. Neither is a reliable read on what a working unit actually trades for. The closely related but distinct 5T10, a 5-gang FM-only tuner, sells in the $125-210 range with occasional highs around $327, and its pricing is frequently confused with 5T50 pricing in online listings. The two are not the same tuner.
No common failure points, capacitor issues, or repair procedures were identified in the available research, so a prospective buyer is largely on their own for condition assessment. Luxman directs spare-parts inquiries to authorized retailers, and availability is not documented. The service manual exists and circulates, which is at least a starting point for anyone planning to bring one back to spec. Because the unit is a PLL synthesizer design with C-MOS memory, the most likely long-term issues are in the digital and power-supply sections rather than the RF front end. That's inference from the architecture, not documented failure data.
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