Luxman LV-103U (1986)

Name: Luxman LV-103u
Brand: Luxman

The LV-103U is a hybrid pre-main amplifier from the Alpine/Luxman era, released in Japan in October 1986 at ¥89,000. It's the follow-up to the LV-103. Period literature describes it as "improved while taking over the concept" of its predecessor, so the hybrid tube/MOS-FET topology stays and the execution gets tightened. It never saw a full U.S. release, and outside Japan it has stayed a fairly obscure piece of Luxman's mid-1980s output.

The circuit is the interesting part. An FET handles the first gain stage. A 3-pole tube runs the pre-driver, chosen for its high voltage resistance and linearity. MOS-FETs drive the output. Luxman claimed that running a voltage-controlled amplifier circuit across all stages eliminates current distortion. The power supply uses what Luxman called the S.T.A.R. circuit. It feeds each amplification stage directly without sharing feed or ground lines, and the signal ground stays independent up to each stage's reference point. A beefed-up power transformer core was part of the refinement over the original LV-103. The phono stage is an MC/MM high-gain equalizer built around a low-noise FET. A CD straight-through function bypasses part of the circuit and routes the CD signal to the power stage at the shortest distance.

Rated output is 80W + 80W into 6 Ω and 50W + 50W into 8 Ω, both 20 Hz-20 kHz, with harmonic distortion claimed at 0.008% (6 Ω, 1 kHz). Phono MM sensitivity is 2.0 mV into 47k Ω. MC is 150 μV into 100 Ω. Line inputs (CD, Tuner, Line) take 150 mV. S/N is quoted at 110 dB IHF for line, 90 dB for MM, and 70 dB for MC. Unusually for an amplifier of this class, the LV-103U carries two AV terminals, one switchable between front and rear, plus a built-in video buffer amplifier able to pass 6 MHz video signals to a monitor or VCR. Signal-processing jacks allow hookup of graphic equalizers or surround processors. Front-panel controls include bass and treble, a loudness button, a stereo/mono mode switch, and a headphone output. It was produced in gray or black, weighs 10.2 kg, and measures 438 × 148 × 353 mm. Power consumption is 170W.

Two things are uncertain. Production years: the October 1986 release is well documented, but at least one database lists the model as 1988-90. Output figures also vary across sources. One European listing claims 2 × 100W and another cites 2 × 65W RMS into 8 Ω, but the Japanese factory specification of 50W + 50W into 8 Ω is the figure used here. Beyond the factory spec sheet, there's little measured review data or documented owner impressions. The audio-database.com listing (in Japanese) remains the most complete technical record, and a 33-page service manual is still in circulation. A capacitor replacement kit and the occasional tested main-amp board turn up for sale, which suggests recapping is the main maintenance task on these today.

Rated output: 80W + 80W (6 Ω); 50W + 50W (8 Ω), 20 Hz–20 kHz
Harmonic distortion: 0.25% (20 Hz–20 kHz)
Inputs: Phono MM/MC, CD, Tuner, Line, 2× AV, signal-processing loop
S/N (IHF): 80 dB (line); 50.5 dB (MM); 42.5 dB (MC)
Power consumption: 170W
Dimensions: 438 × 148 × 353 mm; 10 kg